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Upcoming Events

Event Date and Location Summary
James Bonifacio (CWRU) Tue. January 22nd, 2019
11:30 am-12:30 pm
at Foldy Room
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Shift Symmetries in (Anti) de Sitter Space

Evelyn Hu (Harvard University) Thu. January 24th, 2019
4:00 pm-4:00 pm
at Rockefeller 301
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Defects” as Qubits in SiC: “Inverted Atoms”

There is often a natural assumption that a “perfectly structured” material is required to produce “perfect functioning” of a device, where the function may relate to precision sensing, or the storing or transmission of information. Recently, however, there has been excitement about the performance of defects in crystalline semiconductors such as diamond and SiC. The defects are deviations from perfect, periodic crystalline order, yet can manifest optical emission at a variety of wavelengths, distinctively coupled to long spin coherence times. Rather than focusing on the defect within a semiconductor,

The 2018 Nobel Prizes in Science: What were they given for? Thu. January 31st, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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Kathleen Kash (Physics) on the prize in Physics, Gregory Tochtrop (Chemistry) on the prize in Chemistry and Alex Huang (Department of Pediatrics) on the prize in Physiology or Medicine. 

One-half of the 2018 Nobel Prize in Physics was awarded to Arthur Ashkin, “for the development of optical tweezers and their application to biological systems”. Optical tweezers use the radiation pressure of light to move small particles, and enabled Ashkin to manipulate living cells without damaging them. This work has had major impact in several fields, especially in biology, for example in developing methods to sort healthy from infected or cancerous cells,

Joshua Berger (University of Pittsburgh) Tue. February 5th, 2019
11:30 am-12:30 am
at Foldy Room
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Geoffrey Landis (NASA, Glenn) Thu. February 7th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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Geoffrey Landis (NASA Glenn) Thu. February 7th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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TBA

Riccardo Penco (Carnegie Mellon University) Tue. February 12th, 2019
11:30 am-12:30 pm
at Foldy Room
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Ken Singer (CWRU Physics) Thu. February 14th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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TBA

Aaron Pierce (University of Michigan-Ann Arbor) Tue. February 19th, 2019
11:30 am-12:30 pm
at Foldy Room
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Raman Sundrum (University of Maryland) Thu. February 21st, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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Brian Batell (University of Pittsburgh ) Tue. February 26th, 2019
11:30 am-12:30 pm
at Foldy Room
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Michelle Soares-Santos (Brandeis University) Thu. February 28th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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Cosmology in the era of multi-messenger astronomy with gravitational waves 

Motivated by the exciting prospect of a new wealth of information arising from the first observations of gravitational and electromagnetic radiation from the same astrophysical phenomena, the Dark Energy Survey (DES) has established a search and discovery program for the optical transients associated with LIGO/Virgo events using the Dark Energy Camera (DECam). This talk presents the discovery of the optical transient associated with the neutron star merger GW170817 using DECam and discusses its implications for the emerging field of multi-messenger cosmology with gravitational waves and optical data.

Bhupal Dev (Washington University) Tue. March 5th, 2019
11:30 am-12:30 pm
at Foldy Room
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No Colloquium. APS March Meeting. Thu. March 7th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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No Colloquium. Spring Break. Thu. March 14th, 2019
1:00 am-1:00 am
at Rockefeller 301
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Shixiong Zhang, Indiana University Mon. March 18th, 2019
12:45 pm-1:45 pm
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host: Xuan Gao

Benjamin Monreal (CWRU) Tue. March 19th, 2019
11:30 am-12:30 pm
at Foldy Room
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Subir Sachdev (Harvard University) Thu. March 21st, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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Ira Rothstein (Carnegie Mellon University) Thu. March 28th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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Matthew Fisher (KITP Santa Barbara) Thu. April 4th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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Vladimir Dobrosavljevic, Florida State University Mon. April 8th, 2019
12:45 pm-1:45 pm
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host: Xuan Gao

James Wells (University of Michigan-Ann Arbor) Tue. April 9th, 2019
11:30 am-12:30 pm
at Foldy Room
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Horacio Castillo, Ohio University Mon. April 15th, 2019
12:45 am-1:45 am
at Rockefeller 221 (Les Foldy Room)
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Host: Philip Taylor


External website: https://www.ohio.edu/cas/physastro/faculty/profiles.cfm?profile=castillh
Yue Zhang (Fermilab) Tue. April 16th, 2019
11:30 am-12:30 pm
at Foldy Room
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Allan MacDonald (U Texas Austin) Thu. April 18th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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Moiré pattern physics  in two-dimensional materials

Aldo Romero, West Virginia University, Mon. April 22nd, 2019
12:45 am-1:45 am
at Rockefeller 221 (Les Foldy Room)
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host Walter Lambrecht


External website: https://physics.wvu.edu/faculty-and-staff/faculty/aldo-romero
Sinead Griffin (Lawrence Berkeley Lab) Thu. April 25th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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Bharat Ratra (University of Kansas) Thu. September 5th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
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Spatial Curvature, Dark Energy Dynamics, Neither, or Both?

Experiments and observations over the two last decades have persuaded cosmologists that (as yet undetected) dark energy is by far the main component of the energy budget of the current universe. I review a few simple dark energy models and compare their predictions to observational data, to derive dark energy model-parameter constraints and to test consistency of different data sets. I conclude with a list of open cosmological questions.

Bharat Ratra (Kansas State University) Fri. September 6th, 2019
11:30 am-12:30 pm
at Foldy room
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Cosmological Seed Magnetic Field from Inflation

A cosmological magnetic field of nG strength on Mpc length scales could be the seed magnetic field needed to explain observed few microG large-scale galactic magnetic fields. I first briefly review the observational and theoretical motivations for such a seed field, two galactic magnetic field amplification models, and some non-inflationary seed field generation scenarios. I then discuss an inflation magnetic field generation model. I conclude by mentioning possible extensions of this model as well as potentially observable consequences.

Past Events

Event Date Summary
Colin McLarty (CWRU Philosophy) Thu. January 17th, 2019
4:00 pm-5:00 pm

The two mathematical careers of Emmy Noether

A talk describing Emmy Noether’s life, how she encountered the conservation problem in General Relativity, and how her theorem on it relates to her later larger plan to reorganize all of pure mathematics.

Alexis D. Plascencia (CWRU) Tue. January 15th, 2019
11:30 am-12:30 pm

Tau-philic dark matter coannihilation at the LHC and CLIC 

 

Abstract: We will discuss a set of simplified models of dark matter with three-point interactions between dark matter, its coannihilation partner and the Standard Model particle, which we take to be the tau lepton. The contribution from dark matter coannihilation is highly relevant for a determination of the correct relic abundance. Although these models are hard to detect using direct and indirect detection, we will show that particle colliders can probe large regions in the parameter space. Some of the models discussed are manifestly gauge invariant and renormalizable,

Stephane Coutu (Penn State) Tue. December 4th, 2018
11:30 am-12:30 pm

Abstract: 

Host: Covault

Samo Kralj,Josef Stefan Institute in Ljubljana and University of Maribor, Slovenia, Topological defects in nematic liquid crystals: playground of fundamental physics Mon. December 3rd, 2018
12:45 pm-1:45 pm

Topological defects in nematic liquid crystals: playground of fundamental physics

Samo Kralj

 

1Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia

2Solid State Department, “Jožef Stefan” Institute, Jamova 39, Ljubljana, Slovenia

 

       Topological defects (TDs) are an unavoidable consequence of continuous symmetry breaking phase transitions [1]. They appear at all scales of physical systems, including particle physics, condensed matter and cosmology. Due to their topological origin they display several universalities that are independent of the systems’ microscopic details.

Mark Griswold (CWRU Radiology) Thu. November 29th, 2018
4:00 pm-5:00 pm
Mark B. Wise (Caltech) Tue. November 27th, 2018
11:30 am-12:30 pm
Loop induced inflationary non-Gaussianites that give rise to an  enhanced galaxy power spectrum at small wave-vectors
 
Abstract:  I outline the calculation of non-Gaussian mass density fluctuations that arise from one-loop Feynman diagrams in a de Sitter background.  Their impact on the distribution of galaxies on very large length scales (i.e. l > 200/ h Mpc) is discussed. The role that  symmetries of the de Sitter metric play in determining the form of the power spectrum,  bi-spectrum and tri-spectrum of primordial curvature perturbations is emphasized.

Host: Fileviez Perez

Jure Zupan (University of Cincinnati) Tue. November 20th, 2018
11:30 am-12:30 pm

 Effective field theories for dark matter direct detection

Abstract:

I will discuss the nonperturbative matching of the effective field theory describing dark matter interactions with quarks and gluons to the effective theory of nonrelativistic dark matter interacting with nonrelativistic nucleons. In general, a single partonic operator already matches onto several nonrelativistic operators at leading order in chiral counting. Thus, keeping only one operator at the time in the nonrelativistic effective theory does not properly describe the scattering in direct detection. Moreover, the matching of the axial–axial partonic level operator, as well as the matching of the operators coupling DM to the QCD anomaly term,

Maryam Ghazisaeidi, Ohio State University, High entropy alloys: mechanical properties and phase stability Mon. November 19th, 2018
12:45 pm-1:45 pm

High entropy alloys: mechanical properties and phase stability
Maryam Ghazisaeidi, Department of Materials Science and Engineering, Ohio State University

The term “High entropy” alloys (HEA) refers to a relatively new class of multicomponent—usually
five or more—metallic alloys in equal or near equal atomic concentrations. Instead of ordered
intermetallics, expected from classical physical metallurgy, some HEA systems strikingly crystalize
as single phase solid solutions with simple crystal structures. The complex compositions of these
alloys, and their derivatives, lead to unique properties. They also encourage new ways of viewing
fundamentals of physical metallurgy,

Tracy Slatyer (MIT) Thu. November 15th, 2018
4:00 pm-5:00 pm

The Dark Side of Cosmic Dawn.

Dark matter constitutes more than 5/6 of the matter in the universe, but its nature and interactions remain one of the great puzzles of fundamental physics. Dark matter collisions or decays, occurring throughout the universe’s past, have the potential to produce high-energy particles; such particles may already have reshaped the history of our cosmos, leaving traces of their existence in ionization and heating of the intergalactic medium. I will discuss possible signatures of new dark matter physics in cosmological observations, from the cosmic dark ages to the epoch of reionization,

Jonathan Ouellet (MIT) Tue. November 13th, 2018
11:30 am-12:30 pm

First Results from the ABRACADABRA-10cm Prototype

The evidence for the existence of Dark Matter is well supported by
many cosmological observations. Separately, long standing problems
within the Standard Model point to new weakly interacting particles to
help explain away unnatural fine-tunings. The axion was originally
proposed to explain the Strong-CP problem, but was subsequently shown
to be a strong candidate for explaining the Dark Matter abundance of
the Universe. ABRACADABRA is a proposed experiment to search for
ultralight axion Dark Matter, with a focus on the mass range
10^{-14} ~<

Joe Trodahl, Victoria University of Wellington, Rare-earth nitrides; semiconductors, spin/orbit magnetism, tunnelling MRAM, superconductivity Mon. November 12th, 2018
12:45 pm-1:45 pm

Rare-earth nitrides; semiconductors, spin/orbit magnetism, tunnelling MRAM, superconductivity

Joe Trodahl

 MacDiarmid Institute for Advanced Materials and Nanotechnology

Victoria University of Wellington New Zealand

Controlling the flow of electronic spin in addition to the charge promises speed and power demand advantages. However, there are as yet few “spintronic” devices on the market, in part due to a lack of intrinsic ferromagnetic semiconductors that would permit full exploitation of the coupled spin/charge technology. To date the only full series of such materials are the mononitrides of the lanthanides, the 14 rare-earth elements.

Pino Strangi (CWRU Physics) Thu. November 8th, 2018
4:00 pm-5:00 pm

Plasmons at the Interface Between Physics and Cancer Nanotechnology: The Next Big Thing will be at the Nanoscale

In recent years significant efforts have been made to design and fabricate functional nanomaterials for biomedical applications. These research activities unlocked a complete new research field known as nano-biophotonics. Extreme optics of artificial materials characterized by hyperbolic dispersion allowed to access new physical effects and mechanisms. The unbound isofrequency surface of hyperbolic metamaterials opened the way for virtually infinite photonic density of states and ultrahigh confinement of electromagnetic fields in multilayered nanostructures. This has lead to speed up significantly the spontaneous emission of quantum emitters1,

F. De Angelis, Istituto Italiano di Tecnologia, Genoa, Italy, 3D plasmonic nanostructures for biology and medicine Mon. November 5th, 2018
12:45 pm-1:45 pm

3D plasmonic nanostructures for biology and medicine

Francesco De Angelis

Istituto Italiano di Tecnologia, Genoa, Italy

In this talk we will show our last achievements and future perspectives of distinct class of plasmonic devices devoted to biological and medical applications. Among them, we will introduce the concept of meta-electrodes, namely a nanostructured surface that can work as electrode, a broad band plasmonic antenna, and optimal cellular interface (see Figure 1). We show that meta-electrodes combined with commercial CMOS technology enable high quality intracellular electrical signals on the large network scale of human neuron and cardiomyocytes .

Federico Capasso (Harvard Univ) Thu. November 1st, 2018
4:00 pm-5:00 pm

Flat Optics: from Metalenses to New Polarization Optics and New Routes to Vector Beam Generation 

Arrays of optically thin, sub-wavelength spaced optical elements (meta surfaces) have major potential for wavefront shaping through local control of the phase, amplitude and polarization of light [1]. Flat optics has emerged from this approach [2] with the goals of replacing refractive lenses in most applications requiring aberrations’ correction [3,4] as well as conventional phase plates used in polarization optics [5] and last but not least of providing a new path to the creation of structured light [6]. 

 

Francesc Ferrer (Washington University) Tue. October 30th, 2018
11:30 am-12:30 pm

Primordial black holes in the wake of LIGO

The detection of gravitational waves from the merger of black holes of ~30 solar masses has reignited the interest of primordial black holes (PBHs) as the source of the dark matter in the universe. We will review the existing constraints on the abundance of PBHs and the implications for several fundamental physics scenarios. A small relic abundance of heavy PBHs may play and important role in the generation of cosmological structures, and we will discuss how such a PBH population can be generated by the collapse of axionic topological defects.

Ezekiel Johnston-Halperin, The Ohio State University, Quantum Magnonics in V[TCNE]2 Mon. October 29th, 2018
12:45 pm-1:45 pm

Quantum Magnonics in V[TCNE]2

 

The study of quantum coherent magnonic interactions relies implicitly on the ability to excite and exploit long lived spin wave excitations in a magnetic material. That requirement has led to the nearly universal reliance on yittrium iron garnet (YIG), which for half a century has reigned as the unchallenged leader in high-Q, low loss magnetic resonance, and more recently in the exploration of coherent quantum coupling between magnonic and spin [1] or superconducting [2] degrees of freedom. Surprisingly, the organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]2) has recently emerged as a compelling alternative to YIG.

Mike Martens (CWRU Physics) Thu. October 25th, 2018
4:00 pm-5:00 pm

Conserving Helium: A story of MgB2 superconducting wire and MRI magnets

The fabrication of MgB2 superconducting wire has enabled the development of novel magnet designs for MRI systems. Compared to MRI magnets in use today, which are submerged in a bath of liquid helium, the higher critical temperature (39K) of the MgB2 facilitates conduction cooling which reduces the use of liquid helium by a factor of 100 or more. In collaboration with Hyper Tech Research, a world leader in the manufacture of MgB2 wire, and the Center for Superconducting and Magnetic Materials at the Ohio State University,
Georgia Karagiorgi (Columbia University) Thu. October 18th, 2018
4:00 pm-5:00 pm

The art of neutrino detection: What does it take, and why?

Neutrinos are fundamental blocks of matter. As we’ve learned more and more about them and their properties over the past few decades, we’ve also been led to some important questions about the role of neutrinos in the evolution of our universe; we have also gathered perplexing evidence that makes us question our assumptions about neutrinos in the first place. This talk will review what we know about neutrinos, questions about them that we have yet to answer, and some challenging engineering quests we have embarked on in order to try and settle those questions.

Xiaoju Xu (University of Utah) Tue. October 16th, 2018
11:30 am-12:30 pm

Multivariate Dependent Halo and Galaxy Assembly Bias

Galaxies form in dark matter halos, and their properties and
distributions are connected to the host halos. With a prescription of
the galaxy-halo relation and the theoretically known halo clustering
(e.g., from N-body simulations), galaxy clustering data from large
galaxy surveys can be modeled to learn about galaxy formation and
cosmology. In the above halo-based model, it is usually assumed that
the statistical distribution of galaxies inside halos only depends on
halo mass. However, it is found that in addition to mass halo
clustering also depends on the formation history and environment of
halos,

Sergey Kravchenko, Northeastern University, The latest developments in the field of the metal-insulator transition in 2D Mon. October 15th, 2018
12:45 pm-1:45 pm

Sergey Kravchenko,

Northeastern University

The latest developments in the field of the metal-insulator transition in 2D

Abstract:
Ignited by the discovery of the metal-insulator transition, the behavior of low-disorder two-dimensional (2D) electron systems is currently the focus of a great deal of attention. In the strongly-interacting limit, electrons are expected to crystallize into a quantum Wigner crystal (Wigner, 1934), but no definitive evidence for this effect has been obtained despite much experimental effort over the years. Now we have found two-threshold voltage-current characteristics with a dramatic increase in noise between the two threshold voltages.

Brian Keating (UC San Diego) Thu. October 11th, 2018
4:00 pm-5:00 pm

Fundamental Physics with the Simons Observatory

The Simons Observatory is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. I will describe the scientific goals of the experiment, motivate its design, and forecast its performance. The Simons Observatory will measure the temperature and polarization anisotropy of the cosmic microwave background with arcminute resolution over approximately 40% of the sky in six frequency bands: 27, 39, 93, 145, 225 and 280 GHz. In its initial phase, three small-aperture (0.5-meter diameter) telescopes and one large-aperture (6-meter diameter) telescope will be fielded.

Brad Benson (University of Chicago) Tue. October 9th, 2018
11:30 am-12:30 pm

New Results from the South Pole Telescope

I will give an overview of the South Pole Telescope (SPT), a 10-meter diameter telescope at the South Pole designed to measure the cosmic microwave background (CMB).  The SPT recently completed 10 years of observations, over which time it has been equipped with three different cameras: SPT-SZ, SPTpol, and SPT-3G. I will discuss recent results from the SPT-SZ and SPTpol surveys, including: an update on the SPT Sunyaev-Zel’dovich (SZ) cluster survey, and joint analyses with the optical dark energy survey (DES); a comparison of CMB measurements between SPT-SZ and the Planck satellite;

Tim Linden (Ohio State University) Thu. October 4th, 2018
4:00 pm-5:00 pm

2018 Michelson Postdoctoral Prize Lecture 3: Colloquium 

Indirect Searches for Weakly-Interacting Massive Particles

Recent observations at gamma-ray and radio energies, as well as local observations of charged cosmic-rays, have placed increasingly stringent constraints on the annihilation cross-section of Weakly Interacting Massive Particle (WIMP) dark matter. Excitingly, these studies have begun to rule out the infamous “thermal annihilation cross-section”, where WIMP models are expected to naturally obtain the observed relic abundance. As expected when multiple cutting-edge observations coincide, there is currently tension between different studies. For example, strong limits from gamma-ray searches in dwarf-spheroidal galaxies lie in significant tension with dark matter explanations for the observed “Galactic Center excess” observed near the center of the Milky Way.

Tim Linden (Ohio State University) Tue. October 2nd, 2018
11:30 am-12:30 pm

2018 Michelson Postdoctoral Prize Lecture 2

The Rise of the Leptons: Emission from Pulsars will Dominate the next Decade of TeV Gamma-Ray Astronomy

HAWC observations have detected extended TeV emission coincident with the Geminga and Monogem pulsars. In this talk, I will show that these detections have significant implications for our understanding of pulsar emission. First, the spectrum and intensity of these “TeV Halos” indicates that a large fraction of the pulsar spindown energy is efficiently converted into electron-positron pairs. This provides observational evidence necessitating pulsar interpretations of the rising positron fraction observed by PAMELA and AMS-02.

Tim Linden (Ohio State University) Mon. October 1st, 2018
12:45 pm-1:45 pm

Michelson Postdoctoral Prize Lecture 1

Astrophysical Signatures of Dark Matter Accumulation in Neutron Stars

Over the past few decades, terrestrial experiments have placed increasingly strong limits on the dark matter-nucleon scattering cross-section. However, a significant portion of the standard dark matter parameter space remains beyond our reach. Due to their extreme density and huge gravitational fields, neutron stars stand as optimal targets to probe dark matter-nucleon interactions. For example, over the last few years, the mere existence of Gyr-age neutron stars has placed strong limits on models of asymmetric dark matter. In this talk,

Dan Hooper (Fermilab) Thu. September 27th, 2018
4:00 pm-5:00 pm
The WIMP is Dead. Long Live the WIMP!
 
Abstract: Although weakly interacting massive particles (WIMPs) have long been the leading class of candidates for the dark matter of our universe, the lack of a confirmed detection of these particles has left the community increasingly skeptical of their existence. In this talk, I will ask the following questions: How surprised should we be that WIMPs have not yet been detected? What assumptions might we change in order to explain the lack of any clear signals of dark matter? In light of the current experimental situation,
Mahmoud Parvizi (Vanderbilt University) Tue. September 25th, 2018
11:30 am-12:30 pm

Cosmological Observables via Non-equilibrium Quantum Dynamics in Non-stationary Spacetimes

Abstract: 

In nearly all cases cosmological observables associated with quantum matter fields are computed in a general approximation, via the standard irreducible representations found in the operator formalism of particle physics, where intricacies related to a renormalized stress-energy tensor in a non-stationary spacetime are ignored. Models of the early universe also include a hot, dense environment of quantum fields where far-from-equilibrium interactions manifest expressions for observables with leading terms at higher orders in the coupling. A more rigorous treatment of these cosmological observables may be carried out within the alternative framework of algebraic quantum field theory in curved spacetime,

Alkan Kabakcioglu, Koc University, DNA folding thermo/dynamics with a twist Mon. September 24th, 2018
12:45 pm-1:45 pm

 DNA folding thermo/dynamics with a twist

Alkan Kabakcioglu, Koc University, Istanbul

DNA denaturation is possibly one of the earliest problems in biophysics that grabbed the attention of statistical physicists. The nature of the folding/melting transition has been subject to debate since 60’s until a breakthrough in the past decade mostly settled the question. We recently readdressed the problem for circular DNA (which has a topologically imposed, fixed linking number due to helicity) and found that the melting behavior is qualitatively different from that of the unconstrained DNA with freely dangling ends.

Charles Rosenblatt (CWRU Physics) Thu. September 20th, 2018
4:00 pm-5:00 pm

Manipulation of Topological Defects in Liquid Crystals

 A topological defect (TD) occurs at a wall, line, or point where the relevant order parameter — in our case the liquid crystal’s orientational order parameter — becomes ill-defined, and where this singularity cannot be removed by varying the order parameter continuously. Studies of TDs can be used to obtain values of elastic constants and surface tension, and can serve as an important signature when determining the symmetry of phases. Defect dynamics provide another important field of study, as defect motion is extremely sensitive to boundary effects and provides information about surfaces and impurities.
Miguel Zumalacarregui (UC Berkeley & IPhT Saclay) Tue. September 18th, 2018
11:30 am-12:30 pm

The Dark Universe in the Gravitational Wave Era
Evidence shows that we live in a universe where 95% of the matter and energy is of unknown nature. Right from the onset, Gravitational Wave (GW) astronomy is shaping our understanding of the dark universe in several ways: GW signals of black hole mergers have resurrected the idea of Dark Matter being made of primordial black holes, while multi-messenger GW astronomy has generated novel ways to test Dark Energy and the fundamental properties of gravity. I will discuss the impact of gravitational waves on the landscape of gravitational theories,

no seminar/faculty meeting Mon. September 17th, 2018
12:45 pm-2:00 pm
Laura Grego (Union of Concerned Scientists) Thu. September 13th, 2018
4:00 pm-5:00 pm

Missile Defense and Space Weapons

Missile defenses and space weapons have been pursued at modest levels for many decades, but both are poised to see an enormous increase in funding and scope in the United States. Developments in North Korean nuclear and missile programs are providing justification to build more of existing missile defense systems as well as new types of systems.  And recent policy directs the Pentagon to create a Space Force and to begin building both offensive and defensive space systems.

Missile defense and space weapons are also closely related technologically. Defense systems designed to target ballistic missiles have inherent capabilities as anti-satellite weapons.

Andre De Gouvea (Northwestern Univ.) Fri. September 7th, 2018
12:45 pm-1:45 pm

Chiral Dark Sectors, Neutrino Masses, and Dark Matter

I discuss the hypothesis that there are new chiral fermions particles that transform under a new gauge group. Along the way, I present one mechanism for constructing nontrivial, chiral gauge theory and explore the phenomenology – mostly related to nonzero neutrino masses and the existence of dark matter – associated to a couple of concrete example.

Host: Fileviez Perez

Andre De Gouvea (Northwestern University) Thu. September 6th, 2018
4:00 pm-5:00 pm

The Brave nu World

I review the current theoretical and phenomenological status of neutrino physics. I will discuss our current understanding of neutrino properties, open questions, some new physics ideas behind nonzero neutrino masses, and the challenges of piecing together the neutrino mass puzzle. I will also comment on the new physics reach of the current and the next generation of neutrino oscillation experiments.

Anastasia Fialkov (Harvard Univ.) Tue. August 7th, 2018
11:30 am-12:30 pm

SHINING LIGHT INTO COSMIC DARK AGES

The first billion years is the least-explored epoch in cosmic history. The first claimed detection of the 21 cm line of neutral hydrogen by EDGES (announced at the end of February this year) – if confirmed – would be the first time ever that we witness star formation at cosmic dawn. Join Dr. Fialkov as she discusses theoretical modeling of the 21 cm signal, summarizes the status of the field after the EDGES detection, and shares thoughts on prospects for future detections of this line.

Amy Connolly (The Ohio State University) Tue. May 8th, 2018
11:30 am-12:30 pm
High Energy Neutrino Astronomy through Radio Detection 

Multimessenger astronomy has entered an exciting new era with the recent discovery of both gravitational waves and cosmic neutrinos.  I will focus on neutrinos as particles that can uniquely probe cosmic distances at the highest energies.  While optical Cerenkov radiation has been used for decades in neutrino experiments, the radio Cerenkov technique has emerged in the last 15 years as the most promising for a long-term program to push the neutrino frontier by over a factor of 1000 in energy.   I will give an overview of the current status and future of the radio neutrino program,

Stuart Raby (Ohio State University) Tue. May 1st, 2018
11:30 am-12:30 am

Fitting amu and B physics anomalies with a Z’ and a Vector-like 4th family in the Standard Model

The Standard Model is very successful.  Nevertheless, there are some, perhaps significant, discrepancies with data.

A particularly interesting set of discrepancies hints at new physics related to muons. I will review the data and recent

NP models trying to fit the data.  Then I will discuss a very simple model which is motivated by heterotic string constructions.

Laura Gladstone (CWRU Physics) Thu. April 26th, 2018
4:00 pm-5:00 pm
Report from the International Conference on Women in Physics: Reaching Towards Equity and Inclusion
 
In July 2017, I was one of the US delegates to the IoP International Conference on Women in Physics, held in Birmingham, UK. The conference brought together feminist scientists from around the world to share their work and inspiration, to mentor each other, and to share best practices. Each country’s delegation summarized the status and main obstacles for women physicists in their country. In this talk, I will briefly describe the status within several countries, then explain the issues presented in the US country poster: implicit bias,
Tyce DeYoung (Michigan State University) Tue. April 24th, 2018
11:30 am-12:30 am

First light at the IceCube Neutrino Observatory
The IceCube Neutrino Observatory, the world’s largest neutrino detector, monitors a cubic kilometer of glacial ice below the South Pole Station to search for very high energy neutrinos from the astrophysical accelerators of cosmic rays.  Since its commissioning in 2011, IceCube has discovered a flux of TeV-PeV scale astrophysical neutrinos, at a level with significant implications for our understanding of the dynamics of the non-thermal universe.  The sources of this flux have remained elusive, however.  In the last six months, hints to the identity of at least some of the sources may have begun to emerge,

Wei-Cheng Lee, Binghamton University-SUNY, Orbital Selective Mott Transition in Thin Film VO2 Mon. April 23rd, 2018
12:45 pm-1:45 pm

Orbital Selective Mott Transition in Thin Film VO2

Wei-Cheng Lee

Department of Physics, Applied Physics, and Astronomy, Binghamton University – SUNY

In this talk, evidences of strain-induced modulation of electron correlation effects in the rutile phase of epitaxial VO2/TiO2 will be presented. The strain is engineered by different growth orientations (001), (100), and (110). We find that the hard x-ray photoelectron spectroscopy (HAXPES) reveals significant suppression of the density of states at the Fermi energy in (100) and (110) samples at a temperature well above the metal-insulator transition temperature, but not in the (001) sample.

Jacob Scott (Cleveland Clinic) Thu. April 19th, 2018
4:00 pm-5:00 pm

Learning to perturb the evolutionary mechanisms driving drug resistance in cancer and microbes: an integrated theoretical and experimental approach.

The evolution of resistance remains an elusive problem in the treatment of both cancer and infectious disease, and represents one of the most important medical problems of our time. While the illnesses are different on several non-trivial levels including timescale and complexity, the underlying biological phenomenon is the same: Darwinian evolution. To comprehensively approach these problems, I have focussed my attention on building a broad suite of investigations centered around the causes and consequences of the evolutionary process in these contexts.
Camille Avestruz (Kavli Institute for Cosmological Physics, University of Chicago) Tue. April 17th, 2018
11:30 am-1:30 pm
Computationally Probing Large Structures
We can constrain cosmological parameters by measuring patterns in the large scale structure of our universe, which are governed by the competition between gravitational collapse and the accelerated expansion of our universe.  The most massive collapsed structures are clusters of galaxies, comprised of hundreds to thousands of galaxies.  For galaxy clusters, the telltale cosmological pattern is simply their number count as a function of mass and time.  In this talk, I will discuss the challenges in using galaxy clusters as a probe for cosmology.  We address these challenges through computational methods that explore galaxy formation processes such as energy feedback from active galactic nuclei,
Fac. meeting Mon. April 16th, 2018
12:45 pm-1:45 pm
Dimitar Sasselov (Harvard University) Thu. April 12th, 2018
4:00 pm-5:00 pm
Ocean Worlds: from Familiar to Exotic and Extreme Planets
 
Water is a common molecule in the the galaxy and an abundant bulk component of planets – like Neptune, far from their stars. Liquid water – a precious solvent, might be significantly more rare. Exoplanet exploration is both motivated by the search for surface liquid water and is helping us understand the wide diversity of ocean worlds. Such understanding is necessary if we are to succeed in the search for planetary conditions that could lead to the emergence of life.
Jesse Berezovsky (CWRU Physics) Thu. April 5th, 2018
4:00 pm-5:00 pm

The Broken Symmetry of Music: Applying Statistical Physics to Understand the Structure of Music

The ubiquity of music throughout history and across cultures raises a fundamental question: Why is this way of arranging sounds such a powerful medium for human artistic expression? Though there are myriad musical systems and styles, there are certain characteristics that are nearly universal, including a restriction to a discrete set of sound frequencies (pitches). In this talk, I will present a bottom-up approach to a theory of musical harmony, starting from two basic (and conflicting) principles: a system of music is most effective when it 1.

Hayden Lee (Harvard University) Tue. April 3rd, 2018
11:30 am-12:30 am
Collider Physics for Inflation
Cosmological correlation functions encode the spectrum of particles during inflation, in analogy to scattering amplitudes in colliders. Particles with masses comparable to the Hubble scale lead to distinctive signatures on non-Gaussianities that reflect their masses and spins. In addition, there exists a special class of partially massless particles that have no flat space analog, but could have existed during inflation. I will describe their key spectroscopic features in the soft limits of correlation functions, and discuss scenarios in which they lead to observable non-Gaussianity.
Susan Fullerton, University of Pittsburgh, Using Ions to Control Transport in 2D Materials Mon. April 2nd, 2018
12:45 pm-1:45 pm

Using Ions to Control Transport in 2D Materials

Susan Fullerton, University of Pittsburgh

 

Electrostatic gating of two-dimensional (2D) materials with ions is an effective method to achieve high carrier density (10^13 – 10^14 cm^-2) and excellent gate control by creating an electric double layer (EDL) with large capacitance density (>2 μF/cm^2). I will review our use of EDL gating to investigate transport properties of 2D materials including MoTe2, MoS2 and WSe2, and introduce new device concepts that employ EDL gating as an active device component. These include a monolayer electrolyte for application in flash memory,

Olle Heinonen, Argonne National Laboratories, Quantum Monte Carlo modeling of real materials Fri. March 30th, 2018
3:30 pm-4:30 pm

Quantum Monte Carlo modeling of real materials

Olle Heinonen, Argonne National Laboratory

 

Because of recent advances in algorithms and hardware, it is now possible to do quantum Monte Carol simulations of real materials systems, such as correlated oxides, for which standard density functional theory methods have well-known problems. I will here briefly introduce variational and diffusion Monte Carlo methods, and then discuss some results for correlated oxides as well as for some chemical systems. I will end with discussing on-going developments and an outlook towards the future.

 

 

TBA Thu. March 29th, 2018
4:00 pm-5:00 pm
Benjamin Fregoso, Dept of Physics, Kent State University, Nonlinear photocurrents in two-dimensional ferroelectrics and beyond Wed. March 28th, 2018
12:45 pm-1:45 pm

 Nonlinear photocurrents in two-dimensional ferroelectrics and beyond

Benjamin Fregoso, Dept. of Physics, Kent State University

Abstract:

In recent years, it has become clear the need for efficiently harvesting solar energy. Unfortunately, silicon-based solar cells with high efficiency are very costly. These devices rely on pn-junctions to separate positive and negative charge carries. I this talk, I explore a less known (but very interesting) nonlinear optical effect, so-called `shift current’, to generate large photocurrent beyond the pn-junction paradigm. I will describe the shift-current mechanism in insulators and ferroelectrics and its relation to spontaneous electric polarization.

Segev BenZvi (University of Rochester) Tue. March 27th, 2018
11:30 am-12:30 am

The Latest Results from the HAWC Very High-Energy Gamma-ray Survey
The High Altitude Water Cherenkov (HAWC) observatory, located in central
Mexico, is conducting a wide-angle survey of TeV gamma rays and cosmic
rays from two-thirds of the sky. TeV gamma rays are the highest energy
photons ever observed and provide a unique window into the non-thermal
universe. These very high energy photons allow HAWC to conduct a broad
science program, ranging from studies of particle acceleration in the
Milky Way to searches for new physics beyond the Standard Model. In this
talk,

Sebastian Deffner (Univ Maryland Baltimore County) Thu. March 22nd, 2018
4:00 pm-5:00 pm

Quantum speed limits: from Heisenberg’s uncertainty principle to optimal quantum control

One of the most widely known building blocks of modern physics is Heisenberg’s indeterminacy principle. Among the different statements of this fundamental property of the full quantum mechanical nature of physical reality, the uncertainty relation for energy and time has a special place. Its interpretation and its consequences have inspired continued research efforts for almost a century. In its modern formulation, the uncertainty relation is understood as setting a fundamental bound on how fast any quantum system can evolve. In this Colloquium we will discuss important milestones,

Katy Keenan Applied Physics Division, Physical Measurement Lab National Institute of Standards and Technology Quantitative MRI for Precision Medicine Thu. March 22nd, 2018
2:00 pm-3:00 pm

IMAGING PHYSICS SEMINAR

Katy Keenan
Applied Physics Division, Physical Measurement Lab
National Institute of Standards and Technology

Quantitative MRI for Precision Medicine

The ability of MRI to measure real, physical parameters of interest requires reference standards to ensure accuracy and reproducibility of data. Currently, variability exists across MRI systems, manufacturers, models, software versions, and analysis packages, which impedes comparison of data across patients, centers, and time. To move towards precision medicine, we must be able to determine the threshold of normal compared to disease state with a diagnostically useful uncertainty.

Cliff Cheung (Caltech) Tue. March 20th, 2018
11:30 am-12:30 pm
Unification from Scattering Amplitudes
 
The modern S-matrix program offers an elegant approach to bootstrapping quantum field theories without the aid of an action.  While most progress has centered on gravity and gauge theory, similar ideas apply to effective field theories (EFTs).  Sans reference to symmetry or symmetry breaking, we show how certain EFTs can be derived directly from the properties of the tree-level S-matrix, carving out a theory space of consistent EFTs from first principles.  Furthermore, we argue that the S-matrix encodes a hidden unification of gravity, gauge theory, and EFTs.  In particular, starting from the tree-level S-matrix of the mother of all theories,
Debra McGivney, Dept. Radiology CWRU, Inverse Problems in Medical Imaging Tue. March 20th, 2018
1:00 pm-2:00 pm

IMAGING PHYSICS SEMINAR
Debra McGivney
Research Scientist, Department of Radiology
Case Western Reserve University

Inverse Problems in Medical Imaging

Mathematical inverse problems are used to model a wide variety of practical problems, including problems in medical imaging. Here, the unknown of interest is an image of the inside of the human body, which is not directly observable, but must be reconstructed given measurements made outside of the body. Oftentimes, reconstruction problems in imaging are ill-posed, which can result in errors in the reconstructed solution. Medical imaging plays a vital role in the diagnosis,

Yuan-Ming Lu, The Ohio State University, Tunable Surface States of Topological Materials Mon. March 19th, 2018
12:45 pm-1:45 pm

Tunable Surface States of Topological Materials

Yuan-Ming Lu, The Ohio State University

 

The discovery of topological insulators revealed a large class of topological materials, which exhibit novel surface states with unusual properties. I will discuss some recent progress in engineering surface states of topological materials, focusing on two different systems. The 1st class of materials is three-dimensional Dirac semimetals including Na3Bi and Cd3As2, whose topological surface states can be deformed in these materials by either doping or applying mechanical strain. The 2nd class of materials are spin-orbit coupled quantum magnets,

Spring Break Thu. March 15th, 2018
4:00 pm-5:00 pm
Alexey Tonyushkin University of Massachusetts Boston, Breaking the Rules in Magnetic Particle Imaging and Ultra-High Field MRI Thu. March 15th, 2018
12:30 pm-1:30 pm

IMAGING PHYSICS SEMINAR
Alexey Tonyushkin
University of Massachusetts Boston
Breaking the Rules in Magnetic Particle Imaging
and Ultra-High Field MRI

Magnetic Particle Imaging (MPI) is a new tomographic imaging modality that offers high spatial and temporal resolution. Compared to the other imaging modalities such as MRI/CT/PET, MPI is non-toxic, more sensitive, and fully quantitative technique. To date a few small-bore MPI systems were developed, however, human-size MPI scanner has yet to be built. The major challenge of scaling up of MPI is in high power consumption that is associated with the traditional approach to designing the scanner.

Spring break ( no seminar) Mon. March 12th, 2018
12:45 pm-1:45 pm
Michael Boss, NIST, Quantitative MRI: from Bench to Bedside Mon. March 12th, 2018
4:30 pm-5:30 pm

IMAGING PHYSICS SEMINAR
Michael Boss
National Institute of Standards and Technology
Quantitative MRI: from Bench to Bedside

Quantitative MRI: from Bench to Bedside Magnetic Resonance Imaging (MRI) is an exquisite tool for probing the anatomical structure of the human body. It is also capable of measuring physical parameters such as relaxation times, diffusion and temperature, known as quantitative imaging biomarkers (QIBs). When acquired using methods with known limits of bias and reproducibility, these QIBs allow for comparison of scan data across patients, imaging sites, and time, turning into a powerful tool for clinical trials and patient care to evaluate disease state and treatment response.

APS March Meeting Thu. March 8th, 2018
4:00 pm-5:00 pm
John Beacom (The Ohio State University) Tue. March 6th, 2018
11:30 am-12:30 pm

A New Era for Solar Neutrinos
Abstract: Studies of solar neutrinos have been tremendously important, revealing the nature of the Sun’s power source and that its neutrino flux is strongly affected by flavor mixing.  Nowadays, one gets the impression that this field is over.  However, this is not due to a lack of interesting questions; it is due to a lack of experimental progress.  I show how this can be solved, opening opportunities for discoveries in particle physics and astrophysics, simultaneously.

APS March Meeting ( no seminars) Mon. March 5th, 2018
12:45 pm-1:45 pm
Lindley Winslow (MIT) Thu. March 1st, 2018
4:00 pm-5:00 pm

First Results from CUORE: 

Majorana Neutrinos and the Search for Neutrinoless Double-Beta Decay

The neutrino is unique among the Standard Model particles. It is the only fundamental fermion that could be its own antiparticle, a Majorana particle. A Majorana neutrino would acquire mass in a fundamentally different way than the other particles and this would have profound consequences to particle physics and cosmology. The only feasible experiments to determine the Majorana nature of the neutrino are searches for the rare nuclear process neutrinoless double-beta decay. CUORE uses tellurium dioxide crystals cooled to 10 mK to search for this rare process.

Lindley Winslow (MIT) Wed. February 28th, 2018
1:30 pm-2:00 pm

First Results from CUORE: Majorana Neutrinos and the Search for Neutrinoless Double-Beta Decay
The neutrino is unique among the Standard Model particles. It is the only
fundamental fermion that could be its own antiparticle, a Majorana particle. A
Majorana neutrino would acquire mass in a fundamentally different way than the
other particles and this would have profound consequences to particle physics and
cosmology. The only feasible experiments to determine the Majorana nature of the
neutrino are searches for the rare nuclear process neutrinoless double-beta decay.
CUORE uses tellurium dioxide crystals cooled to 10 mK to search for this rare
process.

APS March Meeting preview: student practice talks Mon. February 26th, 2018
12:30 pm-2:00 pm

Shuhao Liu:  A Temperature Driven Hole-phonon Coupling Enhancement Effect in a Strongly Correlated 2D Hole System.

Kasun V. M. N. G. Premasiri:  Tuning Rashba Spin-orbit Coupling in Few-layer InSe.

Kyle Crowley: Doping and Field Effect in Novel 2D Layered Oxides

Santosh Kumar Radha: Distortion modes in inorganic halide perovskites: to twist or to stretch.

Narasak Pandech: First-principles Investigation of The Role of Organic Molecules Inside The α-phase of Hybrid Halide Perovskite CH3NH3BX3 (B= Pb,

Andrew Stephens, Northwestern U., Separating the role of chromatin from lamins in mechanics and morphology of the cell nucleus Thu. February 22nd, 2018
4:30 pm-5:30 pm

Separating the role of chromatin from lamins in mechanics and morphology of the cell nucleus

Andrew Stephens, Northwestern U.

The nucleus is the 10 µm ellipse compartment in the cell which must properly transduce or resist biophysical
forces to dictate the spatial organization of the 2 meters of genome inside of it. Organization and
mechanotransduction determine the expression profile of genome which dictates cell function. Previous studies
revealed that the two major contributors to nuclear mechanics are lamins, protein intermediate filaments lining
the inner nuclear envelope, and chromatin, the DNA genome and its associated proteins,

Richard Ruiz (IPPP-Durham, UK) Tue. February 20th, 2018
11:30 am-12:30 am

LeftRight Symmetry: At the Edges of Phase Space and Beyond

The LeftRight Symmetric model (LRSM) remains one of the best motivated completions of the Standard Model of Particle Physics. Thus far, however, data from the CERN Large Hadron Collider (LHC) tell us that new particles, if they are still accessible, must be very heavy and/or very weakly coupled. Interestingly, these regions of parameter space correspond to collider signatures that are qualitatively and quantitatively different from those developed in pre-LHC times.

Fac. meeting Mon. February 19th, 2018
12:45 pm-1:45 pm

No seminar physics fac. meeting

Lydia Kisley, Univ. Illinois at Urbana-Champaign, Proteins in nanoporous hydrogels: adsorption, diffusion, and folding Mon. February 19th, 2018
4:30 pm-5:30 pm

Proteins in nanoporous hydrogels: adsorption, diffusion, and folding

Lydia Kisley
Beckman Institute, University of Illinois at Urbana-Champaign
Abstract:  Proteins within nanoporous hydrogels have important biotechnological applications in
pharmaceutical purification, tissue engineering, water treatment, biosensors, and medical
implants. Yet, oftentimes proteins that are functional in solution lose activity when in contact
with soft nanostructured materials due to perturbations in the folded state, conformation,
diffusion, and adsorption dynamics of the protein by the material. We have developed several
unique nanoscale fluorescent spectroscopies to image the heterogeneity of protein dynamics
within hydrogels.
Ilya Gruzberg (Ohio State University) Thu. February 15th, 2018
4:00 pm-5:00 pm

Mysteries of the quantum Hall staircase

Quantum Hall effects are a very rich subject in condensed matter physics with many connections to other areas, intrinsic intellectual beauty, and numerous applications. After more than 35 years after the initial discovery, there are new surprising and unexpected phenomena being discovered in this area, both in experiments and in theory. A visual manifestation of the effects is the plot of the Hall resistance as a function of magnetic field, featuring prominent, precisely quantized steps, also called plateaux, and thereby resembling a staircase. The walk up this staircase is a journey in time,

Andrew J. Long (Kavli Institute for Cosmological Physics, University of Chicago) Tue. February 13th, 2018
11:30 am-12:30 am
Testing baryons from bubbles with colliders and cosmology  
“Why is there more matter than antimatter?”  This simple question is arguably the most longstanding and challenging problem in modern cosmology, but with input from the next generation of particle physics experiments we may finally have an answer!  In the talk I will discuss how precision measurements of the Higgs boson at the LHC and future high energy collider experiments will be used to test the idea that the matter-antimatter asymmetry arose during the electroweak phase transition in the fractions of a second after the big bang.  Other cosmological phase transitions can also provide the right environment for generating the matter excess. 
The 2017 Nobel Prizes: What were they given for? Thu. February 8th, 2018
4:00 pm-5:00 pm

Harsh Mathur (Physics) on the prize in Physics; Phoebe Stewart (Pharmacology) on the prize in Chemistry; Peter Harte (Genetics and Genome Sciences) on the prize in Physiology or Medicine; Mariana Carrera (Weatherhead) on the prize in Economics. 

On 14 September 2015 the LIGO collaboration detected gravitational waves from the merger of a pair of black holes a billion light years distant from the Earth. The discovery constitutes the first direct observation of gravitational waves almost a century after they were predicted by Einstein and is the culmination of a fifty year long experimental quest. LIGO is simultaneously a laboratory for fundamental gravitational physics and an observatory of a new kind that promises to revolutionize astronomy.

Ayres Freitas (University of Pittsburgh) Tue. February 6th, 2018
11:30 am-12:30 am

Radiative Corrections in Universal Extra Dimensions

Universal extra dimensions is an interesting extension of the Standard Model
that is naturally protected from electroweak precision constraints and provides
a natural dark matter candidate. Its phenomenology at the LHC is strongly
affected by radiative corrections. On one hand, QCD corrections are important
for understanding the production of heavy gluons and quarks, which are the
particles with the largest production rates at the LHC. On the other hand,
radiative corrections crucially modify the mass spectrum and interactions of the
heavy resonances. This talk will describe recent progress on both of these
fronts.

David McKeen (University of Pittsburgh) Tue. January 30th, 2018
11:30 am-12:30 am

Neutrino Portal Dark Matter

Dark matter that interacts with the standard model (SM) through the “neutrino portal” is a possibility that is relatively less well studied than other scenarios. In such a setup, the dark matter communicates with the SM primarily through its interactions with neutrinos. In this talk, I will motivate neutrino portal dark matter and discuss some new tests of this possibility.

Maxim Dzero, Kent State University, Spins & Knots: The rise of Topology in f-orbital materials Mon. January 29th, 2018
12:45 pm-1:45 pm

Spins & Knots: The rise of Topology in f-orbital materials

Maxim Dzero

Kent State University

In my talk I will review the key recent theoretical and experimental works on a new class of topological material systems – topological Kondo insulators, which appear as a result of interplay between strong correlations and spin-orbit interactions. I will discuss the history of Kondo insulators is along with the theoretical models used to describe these heavy fermion compounds. The Fu-Kane method of topological classification of insulators is used to show that hybridization between the conduction electrons and localized f-electrons in these systems gives rise to interaction- induced topological insulating behavior.

Anders Johan Andreassen (Harvard University) Tue. January 23rd, 2018
11:30 am-12:30 pm

Tunneling in Quantum Field Theory and the Ultimate Fate of our Universe

One of the most concrete implications of the discovery of the Higgs boson is that, in the absence of physics beyond the standard model, the long-term fate of our universe can now be established through precision calculations. Are we in a metastable minimum of the Higgs potential or the true minimum? If we are in a metastable vacuum, what is its lifetime? To answer these questions, we need to understand tunneling in quantum field theory.This talk will give an overview of the interesting history of tunneling rate calculations and all of its complications in calculating functional determinants of fluctuations around the bounce solutions.

Elshad Allahyarov, Duisburg-Essen University and CWRU, Smectic monolayer confined on a sphere: topology at the particle scale Mon. January 22nd, 2018
12:45 pm-1:45 pm

Prof. Dr. Elshad Allahyarov, 

Duisburg-Essen University, Germany, and  Physics Department  CWRU

Smectic monolayer confined on a sphere: topology at the particle scale

The impact of topology on the structure of a smectic monolayer confined to a sphere is explored by particle-resolved computer simulations of hard rods. The orientations of the particles are either free or restricted to a prescribed director field with a latitude or longitude orderings. Depending on the imprinted topology, a wealth of different states are found including equatorial smectic with isotropic poles, equatorial smectic with empty poles,

Peter Armitage (Johns Hopkins) Thu. January 18th, 2018
4:00 pm-5:00 pm

On Ising’s model of ferromagnetism

The 1D Ising model is a classical model of great historical significance for both classical and quantum statistical mechanics. Developments in the understanding of the Ising model have fundamentally impacted our knowledge of thermodynamics, critical phenomena, magnetism, conformal quantum field theories, particle physics, and emergence in many-body systems. Despite the theoretical impact of the Ising model there have been very few good 1D realizations of it in actual real material systems. However, it has been pointed out recently, that the material CoNb2O6, has a number of features that may make it the most ideal realization we have of the Ising model in one dimension.  

Dragan Huterer (U. Michigan) Fri. December 1st, 2017
12:45 pm-1:45 pm

title and abstract tba

Dragan Huterer (Univ Michigan) Thu. November 30th, 2017
4:00 pm-5:00 pm

New Views of the Universe

I will discuss how progress in cosmology over the past decade has improved our understanding of dark matter, dark energy, and the physics of the early universe. I will particularly concentrate on the developments in mapping out the expansion rate of the universe and the growth of density fluctuations in order to better understand dark energy and, eventually, identify the physics responsible for universe’s accelerated expansion.  The talk will provide basic background and discuss exciting new developments at a level accessible to graduate students.

Samo Kralj, University of Maribor, Impact of intrinsic and extrinsic curvature on membrane shapes Wed. November 29th, 2017
12:30 pm-1:30 pm

Prof. Samo Kralj

University of Maribor, Maribor & Jožef Stefan Institute, Ljubljana, Slovenia

 

 Impact of intrinsic and extrinsic curvature on membrane shapes

Red blood cells (erythrocytes) are present in almost all vertebrates and their main function is the transport of oxygen to the body tissues. Their shape dominantly influences their functionality. In almost all mammals in normal conditions erythrocytes adopt a disk-like (discocyte) shape which optimizes their flow properties in large vessels and capillaries. Experimentally measured values  of  the  relative volume v of stable discocyte shapes  range in a relatively broad window.

Arthur Kosowsky (Pittsburgh) Tue. November 28th, 2017
11:30 am-12:30 pm

title and abstract tba

No seminar, Faculty meeting Mon. November 27th, 2017
12:45 pm-2:00 pm
Farida Selim, Bowling Green State University, Positron Annihilation Spectroscopy and Measurements of Origin of Novel Electronic Phenomena in Semiconductors and Oxides Mon. November 20th, 2017
12:45 pm-1:45 pm

Positron Annihilation Spectroscopy and Measurements of Origin of Novel Electronic Phenomena in Semiconductors and Oxides    

Farida A. Selim, Department of Physics and Astronomy, Bowling Green State University  

Center for Photochemical Sciences, Bowling Green State University

 Positron Annihilation Spectroscopy (PAS) has been established as an effective tool to probe electron states and measure atomic scale defects in solids. However, when combined with other techniques, PAS becomes also a powerful tool for revealing and explaining many interesting electronic phenomena. In our laboratory, we combined PAS with structural and transport measurements as well as with infrared,

A.H. Heuer (CWRU Materials Science and Engineering) Thu. November 16th, 2017
4:00 pm-5:00 pm

Mechanism of Aluminum-Oxide Scale Formation on some High-Temperature Structural Alloys

The formation of Al2O3 scale on high-temperature structural alloys is a subject of immense technological importance, as well as of considerable scientific interest. Contrary to much current thinking in the field, the kinetics of scale growth appear to be controlled by the electrical conductivity of the scales, rather than solely by the diffusion of aluminum and oxygen at grain boundaries. Considerations of band structure thus become of major importance. The atomic structures and the electronic density of states were computed for a group of bi-crystal boundaries using density-functional theory.

Simone Aiola (Princeton) Tue. November 14th, 2017
11:30 am-12:30 pm

Cosmology with ACTPol and AdvACT

The bolometric polarimeter at the focal plane of the Atacama Cosmology Telescope allows us to map the Cosmic Microwave Background (CMB) with high signal-to-noise both in temperature and polarization.  In this talk, I will present the data-reduction pipeline, highlighting the importance of making maximum-likelihood unbiased CMB maps. I will show the two-season ACTPol cosmological results presented in Louis et al. (2017), Sherwin et al. (2017), and Hilton et al. (2017) and describe the current effort to finalize the analysis of the ACTPol dataset. I will conclude with preliminary results from the ongoing AdvACT survey,
Vincent Sokalski, Carnegie Mellon University, A New Kind of Magnetism – The Dzyaloshinskii-Moriya Interaction Mon. November 13th, 2017
12:45 pm-1:45 pm

A New Kind of Magnetism – The Dzyaloshinskii-Moriya Interaction

Vincent Sokalski, Dept. of Materials Science and Engineering, Carnegie Mellon University

Magnetism has had a profound effect on our everyday lives from compass needles in ancient times to the modern hard disc drive in today’s computers.  The existence of magnetic materials is rooted in the Heisenberg exchange interaction energy, , which favors parallel (or anti-parallel) alignment of neighboring spin vectors and their associated magnetic dipole moments as found, for example, in Fe, Ni, and Co.  In the past decade a different type of magnetic exchange came to the forefront of modern physics called the Dzyaloshinskii-Moriya Interaction (DMI) given by ,

Xuan Gao (CWRU Physics) Thu. November 9th, 2017
4:00 pm-5:00 pm

2D Materials: from Semiconductors to Topological Insulators

Abstract: Since the first isolation of one-atom thick graphene, research on two-dimensional (2D) materials with layered crystal structure has exploded over the past decade. One focal point in the recent studies of 2D materials beyond graphene is the development of metal chalcogenides (e.g. MoS2) as 2D semiconductors. In this talk, I will first highlight our exploration of non-transition metal chalcogenides InSe and SnS for future 2D semiconductor applications. While multilayer InSe is demonstrated to be a promising new 2D semiconductor for high performance n-type transistor devices,

Jeanie Lau, The Ohio State University, Spin, Charge and Heat Transport in Low-Dimensional Materials Mon. November 6th, 2017
12:45 pm-1:45 pm

Spin, Charge and Heat Transport in Low-Dimensional Materials

Chun Ning (Jeanie) Lau

Department of Physics, The Ohio State University, Columbus, OH 43210, USA

 

Low dimensional materials constitute an exciting and unusually tunable platform for investigation of both fundamental phenomena and electronic applications. Here I will present our results on transport measurements of high quality few-layer phosphorene devices, and the unprecedented current carrying capacity of carbon nanotube “hot dogs”. In the second half of the talk, I will present our recent observation of robust long distance spin transport through the antiferromagnetic state in graphene.

James Bonifacio (Oxford and CWRU) Tue. October 31st, 2017
11:30 am-12:30 pm

Title: Amplitudes for massive spinning particles
 Abstract: I will review a method for constructing scattering amplitudes for spinning particles and then discuss how these amplitudes can be used to constrain massive gravity and theories containing higher-spin particles.

Peter Lu (Harvard University) Thu. October 26th, 2017
4:00 pm-5:00 pm

Gelation of Particles with Short-ranged Attraction

Nanoscale or colloidal particles are exceptionally important in many realms of science and technology. They can dramatically change the properties of materials, imparting solid-like behavior to a wide variety of complex fluids, from yoghurt to cast ceramics. This behavior arises when particles aggregate to form mesoscopic clusters and networks. The essential component leading to aggregation is an interparticle attraction, which can be generated by many physical and chemical mechanisms. In the limit of irreversible aggregation, infinitely strong interparticle bonds lead to diffusion-limited cluster aggregation (DLCA), long-understood as a purely kinetic phenomenon,

Peter Lu (Harvard University) (Not a Colloquium but of related interest) Wed. October 25th, 2017
5:00 pm-6:00 pm

Lecture co-sponsored by the departments of Physics and Art History, the Baker-Nord Center for the Humanities, and the Cleveland Museum of Art. Note unusual time and venue.

The conventional view holds that geometric star-and-polygon patterns in medieval Islamic architecture were designed using a straightedge and a compass. Peter Lu, a research associate at Harvard University, will present his findings that, instead, a wide variety of patterns with five- and ten-fold symmetry were conceived as tessellations of specific decorated puzzles pieces, called girih tiles, that appear in medieval Islamic architectural scrolls. Beginning in the 12th century, patterns designed with these girih tiles appeared throughout the Islamic world,

Jason Alicea (Caltech) Thu. October 19th, 2017
4:00 pm-5:00 pm

Majorana Materializes 

In 1937 Ettore Majorana introduced the concept of what are now fittingly called Majorana fermions — fermionic particles that are their own antiparticles. Nowadays an active search for condensed-matter analogues of these elusive objects is well underway, motivated by both the prospect of revealing new facets of quantum mechanics and longer-term quantum computing applications. This talk will survey recent advances in this pursuit. In particular, I will describe strategies for “engineering” Majorana platforms from simple building blocks, preliminary experimental successes, and future milestones that reveal foundational aspects of Majorana physics directly relevant for quantum computation.

Lloyd Knox (UC Davis) Tue. October 17th, 2017
11:30 am-12:30 pm

The Standard Cosmological Model: A Status Report

Overall, the standard cosmological model has enjoyed enormous empirical success. But there are  a number of indicators that we might be missing something. These include the large-scale cosmic microwave background (CMB) “anomalies”, and two to three sigma discrepancies between cosmological parameters derived from larger angular scales of the CMB vs. smaller angular scales, CMB lensing potential reconstruction vs. CMB power spectra, data from the Planck satellite vs. data from the South Pole Telescope, and CMB-calibrated predictions for  the current rate of expansion vs. more direct measurements. I will introduce the standard cosmological model,

Eric Stinaff, Ohio University, Opto-electronic studies of novel self-contacted 2D materials based devices Mon. October 16th, 2017
12:45 pm-1:45 pm

Opto-electronic studies of novel self-contacted 2D materials based devices

Eric Stinaff

Department of Physics and Astronomy, Ohio University

Interest in two-dimensional crystals has grown exponentially over the last decade, a testament to their vast technological and scientific potential. In addition to properties such as high mobilities, semiconducting and superconducting behavior, and excellent thermal properties, many of these materials have the potential for novel opto-electronic applications, with large absorption, strong room-temperature emission, non-linear response, and optical control of spin and valley degrees of freedom. In this presentation, we will discuss an experimental investigation of mono-to-few-layer sheets of MoS2 and WS2 employing femtosecond transient absorption spectroscopy (FTAS) and microscopy.

No colloquium this week Thu. October 12th, 2017
4:00 pm-5:00 pm
Rachel Bezanson (Pittsburgh) Tue. October 10th, 2017
11:30 am-12:30 pm
Title: The Surprisingly Complex Lives of Massive Galaxies
 
Abstract: Massive galaxies reside in the densest and most evolved regions of the Universe, yet we are only beginning to understand their formation history. Once thought to be relics of a much earlier epoch, the most massive local galaxies are red and dead ellipticals, with little ongoing star formation or organized rotation. In the last decade, observations of their assumed progenitors have demonstrated that the evolutionary histories of massive galaxies have been far from static. Instead, billions of years ago, massive galaxies were morphologically different: compact, possibly with more disk-like structures,
Michael Fisch, Kent State University, X-ray Experiments in Liquid Crystal Science and Technology Mon. October 9th, 2017
12:45 pm-1:45 pm

X-ray Experiments in Liquid Crystal Science and Technology

Michael Fisch

Kent State University

 

The use of X-rays to study liquid crystals has a long history, and is still of continuing interest.  A brief review of liquid crystals and X-ray diffraction from common liquid crystalline phases will be presented.  Interpretation of the resulting diffraction patterns will be discussed, and some of our current experiments in bent-core molecules and “organic salts will be discussed.  The relationship of these studies to current problems in liquid crystal science and technology will be briefly explored,

Indu Satija (George Mason University) Thu. October 5th, 2017
4:00 pm-5:00 pm

Pure & Poetic: Butterfly in the Quantum World

The Hofstadter butterfly is a fascinating two-dimensional spectral landscape – a graph of the allowed energies of an electron in a two-dimensional crystal in a magnetic field. It is a quantum fractal made up of integers, describing topological states of matter known as the integer quantum Hall states. My butterfly story tells the tale of its discovery by a graduate student named Douglas Hofstadter and discusses its number theoretical, geometrical and topological aspects [1]. I will describe how the integers of the butterfly are convoluted in the Pythagorean triplets and the integer curvature of Apollonian gaskets,

No seminar, faculty meeting Mon. October 2nd, 2017
12:45 pm-2:00 pm
Idit Zehavi (CWRU, Astronomy) Thu. September 28th, 2017
4:00 pm-4:00 pm

Galaxy Clustering and the Galaxy-Halo Connection

In the contemporary view of the Universe, galaxies form and evolve in dark matter halos.  Modern galaxy surveys, most notably the Sloan Digital Sky Survey, have transformed the study of large-scale structure enabling detailed measurements of the spatial distribution of galaxies. I will discuss how we interpret these measurements using contemporary models of galaxy clustering which elucidate the relation between galaxies and dark matter halos. I will further describe one of the main challenges currently facing such analyses and present new results for the dependence of the galaxy content of halos on the assembly history of their host halos.

Tiziana Di Matteo (Carnegie Mellon) Tue. September 26th, 2017
11:30 am-12:30 pm
The next massive galaxy and quasar frontier at the Cosmic Dawn

Many of the advances in our understanding of cosmic structure have come
from direct computer modeling. In cosmology, we need to develop computer
simulations that cover this vast dynamic range of spatial and time
scales. I will discuss recent progress in cosmological hydrodynamic
simulations of galaxy formation at unprecedented volumes and
resolution. I will focus on predictions for the first quasars and
their host galaxies in the BlueTides simulation. 

Maosheng Miao, California State University Northridge, Automatic search versus chemical rules in materials structure study Mon. September 25th, 2017
12:45 pm-1:45 pm

Automatic search versus chemical rules in materials structure study
Maosheng Miao
Department of Chemistry and Biochemistry, California State University Northridge CA,
USA; Beijing Computational Science Research Center, Beijing, China

The increase of the computer power in the past decades not only allow us to calculate
larger systems with higher accuracy in materials studies, but also provide the opportunity
to explore large configuration spaces such as structures and compositions. Automatic
structure searches have been very successful in predicting structures of bulk materials. It
seems out of question whether the automatic search is advantageous over traditional
structure design based on chemical knowledge and intuition.

Jeremy Levy (Univ Pittsburgh) Thu. September 21st, 2017
4:00 pm-5:00 pm

Correlated Nanoelectronics 

The study of strongly correlated electronic systems and the development of quantum transport in nanoelectronic devices have followed distinct, mostly non-overlapping paths.  Electronic correlations of complex materials lead to emergent properties such as superconductivity, magnetism, and Mott insulator phases.  Nanoelectronics generally starts with far simpler materials (e.g., carbon-based or semiconductors) and derives functionality from doping and spatial confinement to two or fewer spatial dimensions.  In the last decade, these two fields have begun to overlap.  The development of new growth techniques for complex oxides have enabled new families of heterostructures which can be electrostatically gated between insulating,

Laura Gladstone (CWRU) Tue. September 19th, 2017
11:30 am-12:30 pm
Neutrinos: cool, cold, coldest
 
In all of particle physics, neutrinos are some of the most ghostly particles we’ve detected. While the story of their discovery was pretty cool in itself, some modern experiments are even cooler. 
 
The IceCube experiment, located at the geographic South Pole, was originally designed to collect astro-particle data, especially by looking for neutrino point sources as potential sources of the highest energy cosmic rays. But because of its immense fiducial volume, IceCube can collect high-statistic neutrino data, and thus measure oscillation parameters with precision that rivals dedicated oscillation experiments. 
Liang Wu, UC Berkeley, MPPL3, Antiferromagnetic resonance and in-gap terahertz continuum in Kitaev Honeycomb magnet α−RuCl3 Fri. September 15th, 2017
12:45 pm-1:45 pm

Antiferromagnetic resonance and in-gap terahertz continuum in Kitaev Honeycone magnet α−RuCl3

Spin-1/2 moments in the antiferromagnetic Mott insulator α-RuCl3 are coupled by strongly anisotropic bond-dependent exchange interactions on a honeycomb lattice. Intense study of α- RuCl3 by inelastic scattering has been driven by the proposal that its low energy excitations may be adiabatically connected to the Majorana quasiparticles that emerge in the exact solution of the Kitaev spin liquid model. In my talk, I will present optical absorption measurements using time- domain terahertz spectroscopy in the range 0.3 to 10 meV that reveal several new features of the low-energy spectrum of α-RuCl3 [1].

Liang Wu (Berkeley); Michelson Postdoctoral Prize Lecture Thu. September 14th, 2017
4:00 pm-5:00 pm

Quantized electro-dynamical responses in topological materials

Although solid-state systems are usually considered “dirty” with impurities and imperfections, it is still the case that macroscopic, quantized phenomena can be observed in the form of the Josephson effect in superconductors and the quantum Hall effect in 2DEG. Combinations of these measurements allow you to determine Planck’s constant and the fundamental charge in a solid-state setting. In my talk, I will show you the observation of a new quantized response in units of the fine structure constant in a new class of material so called “topological insulators” (Tis). First,

Liang Wu, University California Berkeley, MPPL2,Giant nonlinear optical responses in Weyl semimetals Tue. September 12th, 2017
11:30 pm-12:30 pm

Giant nonlinear optical responses in Weyl semimetals

Recently Weyl quasi-particles have been observed in transition metal monopnictides (TMMPs) such as TaAs, a class of noncentrosymmetric materials that heretofore received only limited attention. The question that arises now is whether these materials will exhibit novel, enhanced, or technologically applicable properties. The TMMPs are polar metals, a rare subset of inversion- breaking crystals that would allow spontaneous polarization, were it not screened by conduction electrons. Despite the absence of spontaneous polarization, polar metals can exhibit other signatures, most notably second-order nonlinear optical polarizability, leading to phenomena such as second-harmonic generation (SHG).

Liang Wu, University California Berkeley, MPPL1, Low-energy Electrodynamics of 3D Topological Insulators Mon. September 11th, 2017
12:45 pm-1:45 pm

Low-energy Electrodynamics of 3D Topological Insulators

 

Topological insulators (TIs) are a recently discovered state of matter characterized by an “inverted” band structure driven by strong spin-orbit coupling. One of their most touted properties is the existence of robust “topologically protected” surface states.  I will discuss what topological protection means for transport experiments and how it can be probed using the technique of time- domain THz spectroscopy applied to 3D TI thin films of Bi2Se3.  By measuring the low frequency optical response, we can follow their transport lifetimes as we drive these materials via chemical substitution through a quantum phase transition into a topologically trivial regime [1].

Mike Tamor (Ford Research) Thu. September 7th, 2017
4:00 pm-5:00 pm

History, Geometry and the Future of Mobility

For over a century the personal automobile has served as a highly adaptable transportation tool and an aspirational symbol of wealth and freedom.  However, two megatrends would appear to spell its doom:  climate change with the recognition of the need to reduce CO2 emissions, and urbanization with the unprecedented size and density of new emerging megacities where significant vehicle ownership would result in ‘total gridlock’.  Surprisingly, both of these are actually questions of geometry – and a little physics – informed by the history of cities in the developed world. 

Gabriela Marques, National Observatory of Rio de Janeiro and CWRU Tue. September 5th, 2017
11:30 am-12:30 pm

title and abstract tba

Jun Zhu (Penn State) Thu. August 31st, 2017
4:00 pm-5:00 pm

Quantum valley Hall kink states and valleytronics in bilayer graphene

Conventional field effect transistors control current transmission by controlling the charge of carriers. The advent of two-dimensional materials with hexagonal crystal symmetry offers a new electronic degree of freedom, namely valley, the manipulation and detection of which could potentially be exploited to form new many-body ground states as well as new paradigms of electronic applications. In this talk, I will describe our work in creating valley-momentum locked quantum wires, namely quantum valley Hall kink states, in Bernal stacked bilayer graphene and show the operations of a waveguide,
Condensed Matter Seminar: Jie Gao, Missouri University of Science and Technology (University of Missouri – Rolla) Thu. May 11th, 2017
11:30 am-12:30 pm

Jie Gao

Missouri University of Science and Technology (University of Missouri – Rolla)

Tailoring light-matter interaction with metamaterials and metasurfaces

Metamaterials and metasurfaces with designed subwavelength nanostructures exhibit intriguing electromagnetic phenomena, such as negative refraction, invisible cloaking, sub-diffraction imaging, near-zero permittivity and hyperbolic dispersion. In this talk, I will present our recent work on tailoring light-matter interaction with metamaterials and metasurfaces, including the realization of enhanced spontaneous emission, ultrasensitive molecule detection, strong plasmon-phonon interaction, optical vortex generation and full-color metasurface hologram. These results present opportunities and challenges in understanding new physics of light-matter interaction in those artificially structured optical materials and realizing many unprecedented applications in nanophotonics.

Sarah Shandera (Penn State) Tue. May 9th, 2017
11:00 am-12:00 pm

Cosmological open quantum systems

Our current understanding of the universe relies on an inherently quantum origin for the rich, inhomogeneous structure we see today. Inflation (or any of the alternative proposals for the primordial era) easily generates a universe exponentially larger than what we can observe. In other words, the modes that are observationally accessible make up an open quantum system. I will discuss what we might learn by thinking about the universe in this way, even though the quantum structure is probably not observable.

Paul Butler (Carnegie Institute of Washington) Thu. April 27th, 2017
4:00 pm-5:00 pm

Planets Around Nearby Stars

Modern science began with Copernicus speculating that the Earth is a
planet and that all the planets orbit the Sun.  Bruno followed up by
speculating that the Sun is a star, that other stars have planets, and
other planets are inhabited by life.  For this and other heresies,
Bruno was burned at the stake in a public square in Rome in 1600.
Astronomy and extrasolar planets were a really hot field at the time.

Over the past 20 years more than a thousand extrasolar planets have
been found,

Ema Dimastrogiovanni (CWRU) Tue. April 25th, 2017
11:00 am-12:00 pm

Primordial gravitational waves: Imprints and search

Discussed will be some interesting scenarios for the generation of gravitational waves from inflation and the characteristic imprints we can search with upcoming cosmological observations.

CANCELED: Maosheng Miao, California State University Northridge,Simulate to discover: from new chemistry under high pressure to novel two-dimensional materials Mon. April 24th, 2017
12:45 am-1:45 am

CANCELED. Will be rescheduled.

Simulate to discover: from new chemistry under high pressure to novel two-dimensional materials

 

Maosheng Miao

Department of Chemistry and Biochemistry

California State University Northridge, California 91330, USA

 

The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry, rooted in the atomic shell structure. Within compounds, Group I elements, for example, invariably assume the +1 oxidation state, and their chemical properties differ completely from those of the p-block elements.

Juan de Pablo (University of Chicago) Thu. April 20th, 2017
4:00 pm-5:00 pm
Nanoparticles in liquid crystals, and liquid crystals in nanoparticles.
 
Liquid crystals are remarkably sensitive to interfacial interactions. Small perturbations at a liquid crystal interface can in fact be amplified over relative long distances, thereby providing the basis for a wide range of applications. Our recent research efforts have focused on the reverse phenomenon; that is, we have sought to manipulate the interfacial assembly of nanoparticles or the organization of surface active molecules by controlling the structure of a liquid crystal. This presentation will consist of a review of the basic principles that are responsible for liquid crystal-mediated interactions,
David Pace, General Atomics, San Diego, The Fast and the Furious: Energetic Ion Transport in Magnetic Fusion Devices Wed. April 19th, 2017
12:45 am-1:45 am

The Fast and the Furious: Energetic Ion Transport in Magnetic Fusion Devices

D.C. Pace and the DIII-D National Fusion Facility Team

General Atomics, P.O. Box 85608, San Diego, CA 92186-5608, USA

David Pace

Nuclear fusion has the potential to be an energy source that powers society without generating greenhouse gases or high-level radioactive waste. The tokamak approach to controlled nuclear fusion employs a toroidally-shaped magnetic field configuration to confine plasmas at temperatures beyond 200 million K (20 keV). Future reactors aim to utilize the deuterium-tritium fusion reaction due to its favorable cross-section,
Matthew Johnson (Perimeter Institute) Tue. April 18th, 2017
11:00 am-12:00 pm

Mapping Ultra Large Scale Structure

Anomalies in the CMB on large angular scales could find an explanation in terms of pre-inflationary physics or intrinsic statistical anisotropies. However, due to cosmic variance it is difficult to conclusively test many of these ideas using the primary cosmic microwave background (CMB) alone. In this talk, I will outline a program to place stringent observational constraints on theories that predict ultra-large scale structure or statistical anisotropies using the secondary CMB (the Sunyaev Zel’dovich effect, polarization form the post-reionization era, lensing, etc.) and tracers of large-scale structure. These methods will become accessible with next-generation CMB experiments and planned galaxy surveys.

Louis F. Piper, Binghamton University, Shining new light on old problems in lithium ion batteries Mon. April 17th, 2017
12:45 am-1:45 am

Shining new light on old problems in lithium ion batteries

 

Louis Piper

Binghamton University, State University of New York

 

Improving the energy storage and release of lithium ion battery is largely limited to the cathode (positive electrode).  Commercial high capacity LIBs employ Ni-rich layered oxides (derived from LiCoO2) as cathodes.  In these systems, the reversible energy storage capacity is limited to 1 Li+ per transition metal (i.e. Co3+/4+ redox couple).  However, only 2/3 of Li+ per redox couple are typically intercalated due to capacity retention issues with fast cycling and high voltages. 

Lutz Schimansky-Geier (Humboldt University at Berlin) Thu. April 13th, 2017
4:00 pm-5:00 pm

Active Brownian particles: From individual to collective behavior

Single self-propelled particles as well as ensembles of self-propelled particles are examples of non-equilibrium states and a topic of the interdisciplinary research at the borderline between physics and biology. Interesting examples of self-moving objects come from biology, these are bacteria, eukaryots, amoeba, insects, fishes and animals etc. But also in physics self-moving objects are known, which are active colloids and moving spots in reaction-diffusion systems.

I will review various models of self-propelled particles from a viewpoint of statistical physics. Special attention is payed to the influence of noise on the dynamics of single particles and on the exhibition of spatial structures in groups of interacting moving particles.

David Chuss (Villanova) Tue. April 11th, 2017
11:00 am-12:00 pm

The Cosmology Large Angular Scale Surveyor (CLASS)

Precise observations of the cosmic microwave background have played a leading role in the development of the LCDM model of cosmology, which has been successful in describing the universe’s energy content and evolution using a mere six parameters. With this progress have come hints that the universe underwent an inflationary epoch during its infancy.  Cosmic inflation is predicted to produce a background of gravitational waves that would imprint a distinct polarized pattern on the cosmic microwave background (CMB). Measurement of this polarized signal would provide the first direct evidence for inflation and would provide a means to study physics at energy scales around the predicted GUT scale. 

Nandini Trivedi, The Ohio State University, Novel magnetic phases in spin-orbit coupled oxides Mon. April 10th, 2017
12:45 pm-1:45 pm
Novel magnetic phases in spin-orbit coupled oxides
Nandini Trivedi,
 
Department of Physics, The Ohio State University
 

Abstract: I will discuss puzzles about magnetism in some of the simplest oxide materials with a single electron in the d-orbital.  Starting from a microscopic model of a Mott insulator with both spins and orbitals, I will obtain the effective magnetic Hamiltonian and provide insights into the experimental puzzles. 

Cristina Marchetti (Syracuse) Thu. April 6th, 2017
4:00 pm-5:00 pm

Active Matter: from colloids to living cells

Collections of self-propelled entities, from living cells to engineered microswimmers, organize in a rich variety of active fluid and solid states, with unusual properties. For instance, active fluids can flow with no externally applied driving forces and active gases do not fill their container. In this talk I will describe the behavior of such “active materials”, focusing on two examples of liquid-solid transitions driven by active processes. The first is the formation of cohesive matter with no cohesive forces in collections of purely repulsive active colloids. The second describes the properties of epithelial tissues that exhibit a liquid-solid transition at constant density driven by cell motility,

Donghui Jeong (Penn State) Tue. April 4th, 2017
11:00 am-12:00 pm

Non-linearities in large-scale structure: Induced gravitational waves, non-linear galaxy bias

I will present my recent work on non-linearities in large-scale structures of the Universe. For the first part, I will discuss the gauge dependence of the scalar-induced tensor perturbations and its implication on searching the primordial gravitational wave signature from the large-scale structure. For the second part of the talk, I will give a brief overview of the recent review on large-scale galaxy bias (Desjacques, Jeong & Schmidt, 1611.09787) that contains a complete expression for the perturbative bias expansion that must hold on large scales.

Nate Stern, Northwestern University, Monolayer Semiconductor Opto-Electronics: Controlling Light and Matter in Two-Dimensional Materials Mon. April 3rd, 2017
12:45 pm-1:45 pm

Monolayer Semiconductor Opto-Electronics: Controlling Light and Matter in Two-Dimensional Materials

Nathaniel Stern

Department of Physics and Astronomy, Northwestern University

The discovery of monolayer two-dimensional semiconductors of atomic-scale thickness presents a new two-dimensional landscape in which to play with the interaction between light and matter. These nanomaterials at the extreme limit of surface-to-volume ratio exhibit rich optical phenomenology such as layer dependent bandgaps and degenerate, but distinct, valley-polarized excitonic states. The unique features of atomically-thin materials suggest that these layered systems can be exploited to achieve new regimes of light-matter interactions.

Michael Weiss (CWRU Biochemistry) Thu. March 30th, 2017
4:00 pm-5:00 pm

Origins, Evolution and Biophysics: an Ephemeral Golden Braid

Douglas Hofstradter’s celebrated 1979 book, Gödel, Escher, Bach: An Eternal Golden Braid (“GEB”), presented “a metaphorical fugue on minds and machines in the spirit of Lewis Carroll.”  In this talk we likewise seek to explore implicit themes and hidden connections that unite origins and evolution (in a broad sense) with biophysical principles underlying modern biochemistry and molecular genetics. Three vignettes will be presented in which an evolutionary perspective provides coherence to a clutter of molecular details. Just as GEB sought to decipher how systems acquire meaning despite being made of meaningless elements,

Ben Monreal (CWRU) Tue. March 28th, 2017
11:00 am-12:00 pm

Nuclei, neutrinos, and microwaves: searching for the neutrino mass in tritium decay

When Enrico Fermi published his theory of beta decay in 1934—what we now call the weak interaction—he suggested how experiments could measure the neutrino mass: by looking at the shape of the energy distribution of beta decay electrons.  We’re still doing exactly that!  I will talk about the state of the art of tritium beta decay electron measurements: the KATRIN experiment, which starts science runs soon with a molecular tritium source towards sub-0.3 eV sensitivity; and the Project 8 experiment, which aims to develop a future atomic tritium experiment sensitive to neutrino masses below 0.05 eV.  

Mark Wise (Caltech) Note non-standard time Thu. March 23rd, 2017
4:30 pm-5:30 pm

Dark Matter Bound States and Indirect Dark Matter Signals

Most of the mass density in our universe is not composed of the familiar particles that make up atoms. Rather it is something different that goes by the name dark matter. We have considerable evidence for dark matter, for example, through of its gravitational influence on the motion of stars. The current theory of elementary particles has no candidate for the dark matter and it is probably a new type of particle. A number of experiments search for dark matter including the direct detection experiments which look for its scattering off nuclei.  

Paul Kelly, University of Twente, Turning up the heat in first principles Quantum Spin Transport Wed. March 22nd, 2017
12:45 pm-1:45 pm

Turning up the heat in first principles Quantum SpinTransport

 Paul J. Kelly

Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands

 

The spin Hall angle (SHA) is a measure of the efficiency with which a transverse spin current is generated from a charge current by the spin-orbit coupling and disorder in the spin Hall effect (SHE). In a study of the SHE for a Pt|Py (Py=Ni80Fe20) bilayer using a first-principles scattering approach,

Mauricio Bustamante (CCAPP, OSU) Tue. March 21st, 2017
11:00 am-12:00 pm

Prospecting for new physics with high-energy astrophysical neutrinos

High-energy astrophysical neutrinos, recently discovered by IceCube, are fertile ground to look for new physics.  Due to the high neutrino energies — tens of TeV to a few PeV — we can look for new physics at unexplored energies.  Due to their cosmological-scale baselines — Mpc to Gpc — tiny new-physics effects, otherwise unobservable, could accumulate and become detectable.  Possibilities include neutrino decay, violation of fundamental symmetries, and novel neutrino-neutrino interactions.  I will show that the spectral features, angular distribution, and flavor composition of neutrinos could reveal the presence of new physics and,
No Seminar, APS March Meeting and Spring Break Mon. March 13th, 2017
1:00 am-1:00 am
Herbert Levine (Rice Bioengineering) Thu. March 9th, 2017
4:00 pm-5:00 pm

Can theoretical physics help cancer biology? The case of metastatic spread

In order to spread from the primary tumor to distant sites, cancer cells must undergo a coordinated change in their phenotypic properties referred to as the “epithelial-to-mesenchymal” transition.  We have studied the nonlinear genetic circuits that are responsible for this cellular decision-making progress and propose that the transition actually goes through a series of intermediate states. At the same time, we have formulated motility models that allow for the correlation of state of this network and the cell’s biophysical capabilities. Hopefully, these efforts will help us better understand the transition to metastatic disease and possible treatments thereof.

Robert Caldwell (Dartmouth) Tue. March 7th, 2017
11:00 am-12:00 pm

Cosmology with Flavor-Space Locked Fields

We present new models of cosmic acceleration built from a cosmological SU(2) field in a flavor-space locked configuration. We show that such fields are gravitationally birefringent, and absorb and re-emit gravitational waves through the phenomenon of gravitational wave — gauge field oscillations. As a result, a cosmological SU(2) field leaves a unique imprint on both long-wavelength gravitational waves of primordial origin as well as high frequency waves produced by astrophysical sources. We show that these effects may be detected in the future using the cosmic microwave background and gravitational wave observatories.

Glenn Starkman (Physics) Thu. March 2nd, 2017
4:00 pm-5:00 pm

An Uncooperative Universe: Large Scale Anomalies in the CMB

The Cosmic Microwave Background Radiation is our most important source of information about the early universe. Many of its features are in good agreement with the predictions of the so-called standard model of cosmology — the Lambda Cold Dark Matter Inflationary Big Bang Theory. However, the large-angle fluctuations of the microwave background are uncooperative with “the program” — they continue to exhibit several statistically significant anomalies. On the one hand, if we look at the whole sky the lowest multipoles seem to be correlated both with each other and with the geometry of the solar system.

Francesca F. Serra, Johns Hopkins University, Control of liquid crystals through topography for optics and assembly Mon. February 27th, 2017
12:45 pm-1:45 pm
Control of liquid crystals through topography for optics and assembly 
Dr. Francesca Serra 

Physics and Astronomy 

Johns Hopkins University
 
Soft materials are a promising tool to explore controllable energy landscapes. Liquid crystals, in particular, combine reconfigurability, unique optical properties and the possibility of directing their self-assembly via the bounding surfaces. I will show, for example, how smectic-A liquid crystals under different boundary conditions create microlens arrays made of focal conic defects or light guides in an aqueous solution. Focal conic domains act as gradient refractive index lenses that can be assembled and ordered exploiting topographical cues.
Corbin Covault (CWRU) Thu. February 23rd, 2017
4:00 pm-5:00 pm
A Cosmic Ray Astrophysicist’s Approach to the Optical Search for Extra Terrestrial Intelligence
 
For decades scientists have been searching the skies for signals from extraterrestrial civilizations using large radio telescopes.  Motivation for these searches is strengthened by the discovery that earth-like planets capable of sustaining life are ubiquitous.  Several new initiatives in the Search for Extra-Terrestrial Intelligence are underway.   In particular, some researchers have realized that signals sent at optical wavelengths may be promising as a plausible means of interstellar communications.  Such signals may be sent in the form of nanosecond light pulses generated by large lasers. 
Hamza Balci, Kent State University, A Single Molecule Approach to Study Protein, Small Molecule, and G-Quadruplex Mon. February 20th, 2017
12:45 pm-1:45 pm

A Single Molecule Approach to Study Protein, Small Molecule, and  G-Quadruplex Interactions

Hamza Balci

Kent State University, Physics Department, Kent, OH

 

G-quadruplex (GQ) structures are non-canonical nucleic acid secondary structures that form in guanine-rich segments of the genome, most prominently at telomeres. In addition, several hundred thousand potential GQ forming sequences have been identified in human genome, with particularly higher frequency at promoter regions. When GQ structures (GQs) form at telomeres, they cap chromosome ends and are involved in stabilizing these vulnerable regions. Also, GQs have been shown to regulate transcription and translation level gene expression when they form in promoter regions of DNA and 5′-UTR of RNA,

Thu. February 16th, 2017
4:00 pm-5:00 pm
Matthew Baumgart (Perimeter Institute) Tue. February 14th, 2017
11:00 am-12:00 pm

De Sitter Wavefunctionals and the Resummation of Time

The holographic RG of Anti-De Sitter gives a powerful clue about the underlying AdS/CFT correspondence. The question is whether similar hints can be found for the heretofore elusive holographic dual of De Sitter. The framework of stochastic inflation uses nonperturbative insight to tame bad behavior in the perturbation series of a massless scalar in DS at late times. Remarkably, this fully quantum system loses phase information and exhibits semiclassical dynamics in the leading approximation. Recasting this as a “resummation of time,” we wish understand whether the distributions that result can be thought of as an attractive UV fixed point of a theory living on a spacelike slice of DS.

The 2016 Science Nobel Prizes – What were they given for? Thu. February 9th, 2017
4:00 pm-4:00 pm

Harsh Mathur on the prize in Physics; Michael Hinczewski on the prize in Chemistry; and Alan Tartakoff on the prize in Physiology or Medicine. Followed by a reception. 

Abstracts

The Nobel Prize in Physics for 2016 was awarded to David Thouless, Duncan Haldane and Michael Kosterlitz for the discovery of states of matter and transitions between these states of matter that could not be understood in terms of the conventional Landau paradigm. Harsh will review the Landau paradigm and describe the specific discoveries for which the prize was awarded: the explanation of a mysterious phase transition in films of superfluid helium by Kosterlitz and Thouless;
Andrew Zentner (Pittsburgh) Tue. February 7th, 2017
11:00 am-12:00 pm

The Power-Law Galaxy Correlation Function

For nearly 40 years, the galaxy-galaxy correlation function has been used to characterize the distribution of galaxies on the sky. In addition, the galaxy correlation function has been recognized as very nearly power-law like despite the fact that it is measured over a wide range of scales. In particular, the galaxy correlation function has been measured on very large scales (~30 Mpc), on which density fluctuations are mild and perturbative approaches are appropriate, as well as very small scales (~0.1 Mpc), on which the evolution of the density field of the universe is quite nonlinear.

Saw-Wai Hla, Ohio University, Operating Individual Quantum Molecular Machines Mon. February 6th, 2017
12:45 pm-1:45 pm

Operating Individual Quantum Molecular Machines

Saw-Wai Hla

 Department of Physics & Astronomy, Ohio University, OH 45701, USA

and

Nanoscience and Technology Division, Argonne National Laboratory, IL 60439, USA.

E-mail: hla@ohio.edu , URL: www.phy.ohiou.edu/~hla

 

A recent emergent research direction is the development of complex molecular machines suitable to operate on solid surfaces. Biological machines have the sizes from tens of nanometers to a few microns –a range where classical machine concepts hold while artificially designed molecular machines can be in the size range of a few nanometers or less,

Thu. February 2nd, 2017
4:00 pm-5:00 pm
Kurt Hinterbichler (CWRU) Tue. January 31st, 2017
11:00 am-12:00 pm

Partially Massless Higher-Spin Gauge Theory

The higher spin theories of Vasiliev are gauge theories that contain towers of massless particles of all spins, and are thought to be UV complete quantum theories that include gravity, describing physics at energies much higher than the Planck scale. We discuss Vasiliev-like theories that include towers of massless and partially massless fields. These massive towers can be thought of as partially Higgs-ed versions of Vasiliev theory. The theory is a fully non-linear theory which contains partially massless modes, is expected to be UV complete, includes gravity, and can live on dS as well as AdS.

Mike Boss, NIST, Physics and Impact of Quantitative Magnetic Resonance Imaging Mon. January 30th, 2017
12:45 pm-1:45 pm

Physics and Impact of Quantitative Magnetic Resonance Imaging

Michael Boss,

Applied Physics Division
National Institute of Standards and Technology, Boulder, CO

Each year, millions of U.S. patients are scanned using Magnetic Resonance Imaging (MRI), costing billions of dollars.  The resultant images are typically qualitative, limiting the ability to compare results across patients, time, and scanners. However, a suite of physical parameters (e.g., relaxation times, diffusion coefficients) are interrogable with magnetic resonance, enabling quantitative imaging biomarkers (QIBs). QIBs can provide threshold values for disease diagnosis, allow meaningful measurement of longitudinal change for evaluating treatment response,

Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer Fri. January 27th, 2017
12:45 pm-1:45 pm

Quantum Loop States in Spin-Orbital Models on the Honeycomb and Hyperhoneycomb Lattices

In the quest for quantum spin liquids, the challenges are many: neither is it clear how to look for nor how to describe them, and definitive experimental examples of quantum spin liquids are still missing. In this talk I will show how to devise a realistic model on the honeycomb lattice whose ground state realizes Haldane chains whose physical supports fluctuate, hence naturally providing the hallmark “fractional excitations” of quantum spin liquids. When taken to the three-dimensional hyperhoneycomb lattice, the ground state becomes a full-fledged symmetry-enriched U(1) quantum spin-orbital liquid,

Lucile Savary (MIT) – Michelson Postdoctoral Prize Lecture Thu. January 26th, 2017
4:00 pm-5:00 pm

Quantum Spin Liquids

The search for truly quantum phases of matter is one of the center pieces of modern research in condensed matter physics. Quantum spin liquids are exemplars of such phases. They may be considered “quantum disordered” ground states of spin systems, in which zero point fluctuations are so strong that they prevent conventional magnetic long range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects,

Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer Tue. January 24th, 2017
11:00 am-12:00 pm

Quantum Spin Ice

Recent work has highlighted remarkable effects of classical thermal fluctuations in the dipolar spin ice compounds, such as “artificial magnetostatics.” In this talk, I will address the effects of terms which induce quantum dynamics in a range of models close to the classical spin ice point. Specifically, I will focus on Coulombic quantum spin liquid states, in which a highly entangled massive superposition of spin ice states is formed, allowing for dramatic quantum effects: emergent quantum electrodynamics and its associated emergent electric and magnetic monopoles. I will also discuss how random disorder alone may give rise to both a quantum spin liquid and a Griffiths Coulombic liquid–a Bose glass-like phase.

Michael Snure, AFRL, Two dimensional BN an atomically thin insulator, substrate, and encapsulation layer from growth to application Mon. January 23rd, 2017
12:45 pm-1:45 pm

Two dimensional BN an atomically thin insulator, substrate, and encapsulation layer from growth to application

Michael Snure

Air Force Research Laboratory, Sensors Directorate, Wright Patterson AFB, OH

Since free standing graphene was found in 2004, there has been an explosion of research on atomically thin two dimensional (2D) materials based isolated sheets of layered van der Waals solids.  The spectacular electrical and thermal transport properties of graphene generated a great deal of hype making it a heavily researched material for ultra-high-speed electronics; however, strong interaction with conventional 3D substrates and the lack of a band gap has proven to degrade properties and limit its usefulness in these devices. 

Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer Mon. January 23rd, 2017
4:15 pm-5:15 pm

A New Type of Quantum Criticality in the Pyrochlore Iridates

The search for truly quantum phases of matter is one of the center pieces of modern research in condensed matter physics. Quantum spin liquids are exemplars of such phases. They may be considered “quantum disordered” ground states of spin systems, in which zero point fluctuations are so strong that they prevent conventional magnetic long range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects,

Kathy Kash (CWRU Physics) Thu. January 19th, 2017
4:00 pm-5:00 pm

Nitride Semiconductors: Beyond the Binaries

The binary nitride semiconductors and their alloys have led to transformations in both lighting and power electronics. They have also given us new physics such as polarization-induced topological insulators. But nitride semiconductors can be built of more than two elements. What new science and technology might we expect from such increased complexity? 

Claire Zukowski (Columbia U.) Tue. January 17th, 2017
11:00 am-12:00 pm

Emergent de Sitter Spaces from Entanglement Entropy

A theory of gravity can be holographically “emergent” from a field theory in one lower dimension. In most known cases, the gravitational theory lives in an asymptotically anti- de Sitter spacetime with very different properties from our own de Sitter universe. I will introduce a second emergent “auxiliary” spacetime constructed from the entanglement entropy of subregions in the field theory. In 2d, this auxiliary space is either a de Sitter spacetime or its various identifications. The modular Hamiltonian, which encodes information about the entanglement properties of a state in the field theory,

Pavel Fileviez Perez (CWRU Physics) Thu. December 8th, 2016
4:00 pm-5:00 pm

New Physics and Unification of Forces

The unification of fundamental forces in nature is one of the most appealing ideas for physics beyond the Standard Model of particle physics. I discuss the beautiful idea of grand unified theories where one can understand the origin of the Standard Model interactions. The experimental predictions are discussed in detail in order to understand the testability of these theories. I discuss an alternative new idea which could change the way we think about physics beyond the Standard Model. The predictions for particle physics experiments and cosmology are discussed.

Beatrice Bonga (Penn State) Tue. December 6th, 2016
11:00 am-12:00 pm

The closed universe and the CMB
Cosmic microwave background (CMB) observations put strong constraints on the spatial curvature via estimation of the parameter $\Omega_k$. This is done assuming a nearly scale-invariant primordial power spectrum. However, we found that the inflationary dynamics is modified due to the presence of spatial curvature leading to corrections to the primordial power spectrum. When evolved to the surface of last scattering, the resulting temperature anisotropy spectrum shows deficit of power at low multipoles ($\ell<20$). This may partially explain the observed $3 \sigma$ anomaly of power suppression for $\ell <30$. Since the curvature effects are limited to low multipoles,

Christopher Wolverton, Northwestern University, Accelerating Materials Discovery with Data-Driven Atomistic Computational Tools Mon. December 5th, 2016
12:45 pm-1:45 pm

Accelerating Materials Discovery with Data-Driven Atomistic Computational Tools

Chris Wolverton

Dept. of Materials Science and Eng., Northwestern University, Evanston, IL (USA)

c-wolverton@northwestern.edu

 

Many of the key technological problems associated with alternative energies (e.g., thermoelectrics, advanced batteries, hydrogen storage, etc.) may be traced back to the lack of suitable materials. Both the materials discovery and materials development processes may be greatly aided by the use of computational methods, particular those atomistic methods based on density functional theory (DFT).   Here, we present an overview of our recent work utilizing high-throughput computation and data mining approaches to accelerate materials discovery,

Mike Hinczewski (CWRU Physics) Thu. December 1st, 2016
4:00 pm-5:00 pm
Yi-Zen Chu (University of Minnesota, Duluth) Tue. November 29th, 2016
11:00 am-12:00 pm

Causal Structure Of Gravitational Waves In Cosmology

Despite being associated with particles of zero rest mass, electromagnetic and gravitational waves do not travel solely on the null cone in generic curved spacetimes. (That is, light does not always propagate on the light cone.) This inside-the-null-cone propagation of waves is known as the tail effect, and may have consequences for the quantitative prediction of gravitational waves from both in-spiraling binary compact stars/black holes and “Extreme-Mass-Ratio” systems. The latter consists of compact objects orbiting, and subsequently plunging into, the horizons of super-massive black holes astronomers now believe reside at the center of many (if not all) galaxies —

Marie-Charlotte Renoult, Université de Rouen, Free falling jets of a viscoelastic solution Wed. November 23rd, 2016
12:45 pm-1:45 pm

Title: Free falling jets of a viscoelastic solution
Prof. Marie-Charlotte Renoult
Université de Rouen, France

Abstract:

We conducted free falling jet experiments of a Newtonian solution with a polymer additive, i.e., a viscoelastic solution.Viscoelastic jets usually break up with the formation of beads-on-a-string (BOAS) structures, where large beads are connected by thin threads. These structures form when the polymer solution begins to exhibit strain-hardening, i.e., an increase in extensional viscosity with extensional rate. Associated with this viscoelastic property is a characteristic relaxation time.In this presentation, two methods of image analysis will be presented: a shape analysis and a multi-scale analysis that are applied to a large number of free falling jet visualisations performed at different jet velocities.The results obtained demonstrate the power of these two experimental techniques to gain a deeper insight into BOAS formation and to probe complex liquid rheology such as the subtle measurement of the polymer relaxation time.

Daniel Winklehner (MIT) Tue. November 22nd, 2016
11:00 am-12:00 pm

On the development and applications of high-intensity cyclotrons in neutrino physics and energy research

The cyclotron is one of, if not the, most versatile particle accelerator ever conceived. Based on the (then revolutionary) principle of cyclic acceleration using RF frequency alternating voltage on a so-called dee, while particles are forced into circular orbits by a strong vertical magnetic field, many varieties have been developed in the 84 years since their invention by Lawrence in 1932. The fact that they are still around and oftentimes in a form that has been proposed many years ago is a testimony to their robustness and versatility.

Keji Lai, Univ of Texas, Austin/Microwave Imaging of Edge States and Electrical Inhomogeneity in 2D Materials Mon. November 21st, 2016
12:45 pm-1:45 pm

The understanding of various types of disorders in 2D materials, including dangling bonds at the edges, defects in the bulk, and charges in the substrate, is of fundamental importance for their applications in electronics and photonics. Because of the imperfections, electrons moving on the 2D plane experience a spatially non-uniform Coulomb environment, whose effect on the charge transport has not been microscopically probed. Using a non-invasive microwave impedance microscope with ~100nm resolution and ~1nS sensitivity, we can visualize the spatial evolution of the insulator-to-metal transition in mono-layer and few-layer MoS2 field-effect transistors. As the transistors are gradually turned on, electrical conduction emerges initially at the edges before appearing in the bulk,

Robert Owen (Oberlin College) Thu. November 17th, 2016
4:00 pm-4:00 pm

Numerical Relativity and Gravitational Radiation from Binary Black Hole Mergers

In September of 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) made the first-ever direct detection of gravitational waves, propagating ripples in the structure of spacetime itself, confirming a nearly century-old prediction of Einstein’s general relativity, and providing an entirely new medium for astronomical observations. The waves, from these particular events and from others like them to come, encode information about the fully nonlinear dynamics of spacetime itself, as they appear to arise from collisions of vacuum black holes. Computational simulation of these events, via a family of techniques known as Numerical Relativity,

Austin Joyce (Kavli Institute for Cosmological Physics, Chicago) Tue. November 15th, 2016
11:00 am-12:00 pm

Soft limits, asymptotic symmetries, and inflation in Flatland

There has been much recent interest in soft limits, both of flat space S-Matrix elements and of cosmological correlation functions. I will discuss the physics probed by soft limits in cosmology and explore the connection between cosmological soft theorems and asymptotic symmetries. These ideas will be illustrated by a simple example: inflation in 2+1 dimensions.

Salah Eddine Boulfelfel, Georgia Institute of Technology, Atomic-Scale Modeling of Activated Processes in the Solid State Mon. November 14th, 2016
12:45 pm-1:45 pm

Atomic-Scale Modeling of Activated Processes in The Solid State

Salah Eddine Boulfelfel

School of Chemical and Biomolecular Engineering

Georgia Institute of Technology

In the practice of solid-state chemistry, processes either thermally-activated or induced by external high-pressure are common events. Often, the simplicity of the material’s structure involved in the activated process is in contrasts with the theoretical and experimental difficulties in assessing its mechanism. Large hysteresis effects, nucleation and growth scenarios, and first-order kinetics require dedicated computational approaches in order to correctly unravel the complex nature of activated process at the atomistic level of details.

Marija Drndic (University of Pennsylvania) Thu. November 10th, 2016
4:00 pm-5:00 pm

2D Materials Nanosculpting and Bioelectronics Applications

Electron beams constitute powerful tools to shape materials with atomic resolution inside a transmission electron microscope (TEM). I will describe experiments where we push the limits of device size to atomic scale in 2D materials beyond graphene (MoS2, WS2, MoTe2, black phosphorous) and expand their function and precision, while addressing fundamental questions about structure and properties at nanometer and atomic scales. Experiments are performed in situ and ex situ TEM. In situ TEM experiments include fabrication of nanoribbons and field-effect-transistors from novel two-dimensional materials down to sub-nm widths.

Rachel Rosen (Columbia University) Tue. November 8th, 2016
11:00 am-12:00 pm

Non-Singular Black Holes in Massive Gravity

When starting with a static, spherically-symmetric ansatz, there are currently two types of black hole solutions in massive gravity: (i) exact Schwarzschild solutions which exhibit no Yukawa suppression at large distances and (ii) solutions which contain coordinate-invariant singularities at the horizon.  In this talk, I will present new black hole solutions which have a nonsingular horizon and can potentially be matched to Yukawa asymptotics at large distances.  These solutions recover Schwarzschild black holes in the massless limit and are thus observationally viable.”

Jim Andrews, Youngstown State University, Coherent Perfect Polarization Rotation–Beyond the Anti-Laser Mon. November 7th, 2016
12:45 pm-1:45 pm

We describe the distinguishing characteristics of coherent perfect optical conversion processes using two-beam interference, as compared to single-beam ‘critical coupling’ processes.  We extend the application of two-port coherent conversion processes to magneto-optical (Faraday) rotation in structured systems and present our recent laboratory demonstration of coherent perfect polarization rotation (CPR) which is a conservative, reversible counterpart to coherent perfect absorption (CPA, or the so-called ‘anti­laser’). conclude with a brief summary of theoretical studies suggesting a CPR-based miniaturization of optical isolators and the extension of coherent perfect  phenomena in non-linear optics.

Tao Han (University of Pittsburgh) Fri. November 4th, 2016
11:00 am-12:00 pm

Splitting and showering in the electroweak sector

We derive the splitting functions for the Standard Model electroweak sector at high energies, including the fermions, massive gauge bosons and the Higgs boson. We study the class of functions with the “ultra-collinear” behavior that is a consequence of the electroweak symmetry breaking. We stress the leading-order corrections to the “Goldstone-boson Equivalence Theorem”. We propose a novel gauge, dubbed the “Goldstone Equivalence Gauge” that practically as well as conceptually disentangles the effects from the Goldstone bosons and the gauge fields. We also demonstrate a practical scheme for multiple electroweak boson production via showering at high energies.

Tao Han (University of Pittsburgh) Thu. November 3rd, 2016
4:00 pm-5:00 pm
Physics Motivations for Future Colliders
With the milestone discovery of the Higgs boson at the CERN LHC, high energy physics has entered a new era. The Higgs boson is the last member in the “Standard Model” (SM) of particle physics, which describes the physical phenomena at high energies to a very high accuracy. The completion of the Standard Model implies, for the first time ever, that we have a relativistic, quantum-mechanical, self-consistent theoretical framework, valid up to exponentially high energies, perhaps to the Planck scale. Yet, there are compelling reasons, both from observations and from theoretical considerations,
Samo Kralj, University of Maribor, Effective Topological Charge Cancellation Mechanism Mon. October 31st, 2016
1:00 pm-2:00 pm

Effective Topological Charge Cancellation Mechanism

Samo Kralj1,2

1FNM, University of Maribor, Koroška 160, 2000 Maribor, Slovenia

2Jožef Stefan Institute, Jamova 39,1000 Ljubljana, Slovenia

Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions [1]. Topological origin makes their key features independent of systems’ microscopic details and therefore TDs display many universalities. In general, TDs have strong impact on material properties and play significant role in several technological applications.

Andrew Rappe (University of Pennsylvania) Thu. October 27th, 2016
4:00 pm-5:00 pm

Slush Structure and Dynamics in a Relaxor Ferroelectric

Ferroelectric materials undergo solid-solid structural phase transitions between phases with aligned dipoles and randomly oriented dipoles. Incorporating quenched Coulombic disorder by varying the charge of the ions on the lattice disrupts and changes the  of this transition; instead of a sharp transition in a small temperature range, these oxide alloys exhibit "relaxed" transition over 100-200 K and are called "relaxor ferroelectrics." In this talk I will describe how a first-principles based multi-scale model can reveal the dynamic and statically correlated motions of ions that lead to relaxor behavior,
Patrick Woodward, The Ohio State University, The magnetism of double perovskites containing osmium and rhenium Mon. October 24th, 2016
12:45 pm-1:45 pm

 

Patrick M. Woodward

Department of Chemistry and Biochemistry, The Ohio State University

Over the past several years we have been synthesizing and studying the magnetic properties of A2MOsO6 and A2MReO6 (Mg, Zn, Cr, Fe, Co, Ni) double perovskites in a quest to understand how the sign and strength of the superexchange interactions change as a function of the relative filling of the 3d and 5d orbitals, as well as the geometry of the crystal structure. In double perovskites where the 5d ion is the only magnetic ion we find that spin-orbit coupling plays a role,

Jim Van Orman (CWRU EEES) Thu. October 20th, 2016
4:00 pm-5:00 pm

Simulating Planetary Interiors in the Lab

This talk will provide an overview of experimental studies on the properties of planetary materials at high pressures, and the constraints they provide on the structure and evolution of planetary interiors.

Sean Bryan (Arizona State University) Tue. October 18th, 2016
11:00 am-12:00 pm

Cosmology with Millimeter Wave LEKIDs: CMB, Spectroscopy, and Imaging with TolTEC

Millimeter-wave cameras offer a unique window on the history and dynamics of the universe. Observations of CMB polarization are setting new constraints on cosmic inflation and gravitational lensing. Imaging and spectroscopy in millimeter waves measures individual galaxies through their bolometric flux as well as C+/CO line strengths. In this talk, I will discuss aluminum LEKID detectors that can be used for all of these applications. The feed structures are directly machined in metal, and the detectors are made with a single-layer process. Lab measurements show that the 150 GHz dual-polarization detectors have photon-noise limited sensitivity,

Mark Newman (University of Michigan) Thu. October 13th, 2016
4:00 pm-5:00 pm

Paul Erdos, Kevin Bacon, and the Six Degrees of Separation: The Statistical Physics of Networks

There are networks in every part of our lives: the Internet, the power grid, the road network, networks of friendship or acquaintance, ecological networks, biochemical networks, and many others.  As large-scale data on these networks have become available in the last few years, a new science of networks has grown up combining observations and theory and drawing heavily on ideas from physics, to shed light on systems ranging from bacteria to the whole of human society.  This talk will give an introduction to this rapidly-growing interdisciplinary branch of science,

Stacy McGaugh (CWRU Astronomy) [note time] Tue. October 11th, 2016
11:00 am-12:00 pm

*Note that the seminar may be pushed back to 11:30-12:30.

The Radial Acceleration Relation in Rotationally Supported Galaxies

We report a correlation between the radial acceleration traced by rotation curves and that predicted by the observed distribution of baryons. The same relation is followed by 2693 points in 153 galaxies with very different morphologies, masses, sizes, and gas fractions. The correlation persists even when dark matter dominates. Consequently, the dark matter contribution is fully specified by that of the baryons. The observed scatter is small and largely dominated by observational uncertainties. This radial acceleration relation is tantamount to a natural law for rotating galaxies.
Nayana Shah, University of Cincinnati, Manifestations of spin-orbit coupling and topology in out-of-equilibrium hybrid superconducting systems Mon. October 10th, 2016
12:45 pm-1:45 pm

Recently there has been a lot of excitement generated by the possibility of realizing and detecting Majorana fermions within the arena of condensed matter physics and its potential implication for topological quantum computing.  Although already at the end of twentieth century emergent Majorana end-states were shown to exist in a theoretical model of spinless p-wave superconductor (Kitaev) chain, it was only a decade later that proposals to experimentally realize such a model emerged. These were motivated by the discovery of topological insulators that ushered a new era of so-called symmetry-protected topological phases but also stemmed from existent studies of hybrid superconductor-ferromagnet systems that form the basis of another highly active area of superconducting spintronics.

John Monnier (University of Michigan) Thu. September 29th, 2016
4:00 pm-5:00 pm

Imaging the Surfaces of Stars

Under even the best atmospheric conditions, telescope diffraction fundamentally limits the angular resolution for astronomical imaging. Using interferometry (Go, Michelson!), we can coherently combine light from widely-separated telescopes to overcome the single-telescope diffraction limit to boost our imaging resolution by orders of magnitude. I will review recent technical and scientific breakthroughs made possible by the Michigan Infrared Combiner of the CHARA Array on Mt. Wilson, CA, with baselines of 330 meters allowing near-infrared imaging with sub-milli-arcsecond resolution. I will present the first resolved images of main sequence stars besides the Sun,

Zhaoning Song, University of Toledo,The Formation and Degradation of Metal Halide Perovskites Mon. September 26th, 2016
12:45 pm-1:45 pm

Solar cells based on organic-inorganic metal halide perovskite materials, such as methylammonium lead iodide (CH3NH3PbI3), have been the subject of intense investigation during the past 5 years due to high power conversion efficiencies (>22%) and relatively low manufacturing costs. Never before has the field of photovoltaics (PV) seen such rapid and exciting progress. The results are surprising because various low-temperature, solution-based processing methods have been successful in fabricating high-efficiency devices. Nevertheless, much of the work in this area has focused on device performance optimization and there is a lack of basic understanding of underlying physics and chemistry.

Kurt Hinterbichler (CWRU Physics) Thu. September 22nd, 2016
4:00 pm-5:00 pm

Massive Gravitons, the Cosmological Constant and New Directions in Gravity

The solution to the cosmological constant problem may involve modifying the very long-range dynamics of gravity by adding new degrees of freedom. As an example of a conservative such modification, we consider the possibility that the graviton has a very small mass. Massive gravity has received renewed interest due to recent advances which have resolved its traditional problems. It has some peculiar and unexpected features, and it points us towards a different way of thinking about the universe on large scales.

Henriette Elvang (University of Michigan) Tue. September 20th, 2016
11:00 am-12:00 pm

Scattering amplitudes and soft theorems

I will give a pedagogical introduction to the spinor helicity formalism which provides a very efficient tool for studies of on-shell scattering amplitudes in 4 dimensions. The power of this formalism will be demonstrated in a new analysis of soft photon and soft graviton theorems.

Director: Peter Galison (Harvard). Movie. Note unusual end time. Thu. September 15th, 2016
4:00 pm-5:30 pm

Containment

Abstract

Can we contain some of the deadliest and most long-lasting substances ever produced? Left over from the Cold War are a hundred million gallons of highly radioactive sludge, thousands of acres of radioactive land, tens of thousands of unused hot buildings, all above slowly spreading deltas of contaminated ground water. Stocked around 400 reactors (worldwide) are spent fuel assemblies, growing at a rate of 12,000 tons per year—each one radioactive enough (if unprotected) to kill a carload of people driving by it at full tilt. Not a single country in the world has a well worked-out plan about what to do with the waste stream of such deadly and long-lived materials (plutonium has a halflife of 24,000 years).

Bob Brown (CWRU) Tue. September 13th, 2016
11:00 am-12:00 pm

Understanding Color-Kinematics Duality with a New Symmetry: From Radiation Zeros to BCJ

I discuss a new set of symmetries obeyed by tree-level gauge-theory amplitudes involving at least one gluon. The symmetry acts as a momentum-dependent shift on the color factors of the amplitude. Using our previous development of radiation vertex expansions, we prove the invariance under this color-factor shift of the n -gluon amplitude, and in fact for any amplitudes involving at least one massless gauge boson and any number of massless or massive particles in arbitrary representations of the gauge group with spin zero,

Richard Schaller (Northwestern University). Not a physics colloquium but of potential interest to physicists. Note unusual location and time. Thu. September 8th, 2016
4:00 pm-6:00 pm

Chemistry Colloquium: Electronic and Thermal Interconversion and Migration in Energy-Relevant Materials

In order to produce energy efficient devices, thorough understanding of fundamental desired and undesired processes of energy and heat interconversion and migration are needed. I will present studies using time-resolved optical methods such as absorption and emission as functions of sample temperature or photon energy that aim to arrive at insights regarding energy transfer, electron transfer, and electron-phonon and phonon-phonon scattering events. Materials examined include nanoscale 0D and 2D semiconductors, bulk phase perovskites, as well as some plasmonic structures.

Raymond Stora’ Last Discovery — Bryan Lynn (CWRU) Tue. September 6th, 2016
11:00 am-12:00 pm

I will discuss Raymond Stora’s final work on new Ward-Takahashi Identities of U(1) gauge theory.

Bryan Lynn (CWRU and University College London) Tue. September 6th, 2016
11:00 am-12:00 pm

Raymond Stora’s last work

Excursion Sets, Peaks and Other Creatures: Improved Analytical Models of LSS – Marcello Musso Tue. May 3rd, 2016
11:30 am-12:30 pm

I will present recent developments in analytical methods to predict abundance, clustering, velocities and bias of Dark Matter halos. In the standard analytical approach, halos are identified either with sufficiently high peaks of the initial matter density field, or with the largest spheres enclosing a sufficiently high density. I will revise the physical assumptions leading to this standard picture, and show how a careful statistical implementation of the model of collapse (even in the simple spherically symmetric case) leads to a surprisingly rich structure. This allows to make simple – yet remarkably accurate – analytical predictions for halo statistics, a necessary ingredient on the road to precision cosmology.

Observation Of Interlayer Phonons in Transition Metal Dichalogenide Atomic Layers and Heterostructures – Rui He Mon. May 2nd, 2016
12:30 pm-1:30 pm

Interlayer phonon modes in atomically thin transition metal dichalcogenide (TMD) heterostructures were observed for the first time. We measured the low-frequency Raman response of MoS2/WSe2 and MoSe2/MoS2 heterobilayers. We discovered a distinctive Raman mode (30 – 35 cm-1) that cannot be found in any individual monolayers (see Fig. 1). By comparing with Raman spectra of bilayer (2L) MoS2, 2L MoSe2 and 2L WSe2, we identified the new Raman mode as the layer breathing mode (LBM) arising from the perpendicular vibration between the two TMD layers. The LBM only emerges in bilayer regions with atomically close layer-layer proximity and clean interface.

Do We Understand the Universe – Raul Jimenez Tue. April 26th, 2016
11:30 am-12:30 pm

Observations of the cosmos provide a valuable tool to study the fundamental laws of nature. The future generation of astronomical surveys will provide data for a sizeable fraction of the observable sky. This rich data set should provide the means to answer fundamental questions: what are the laws of physics at high energies in the Early Universe? What is the nature of neutrinos? What is dark matter? What is dark energy? Why are there baryons at all? In this talk I will review the current status, provide a roadmap for future prospects and discuss in detail how we might approach the task of extracting information from the sky to answer the above questions.

Do We Understand the Universe? – Raul Jimenez Tue. April 26th, 2016
11:30 am-12:30 pm

Observations of the cosmos provide a valuable tool to study the fundamental laws of nature. The future generation of astronomical surveys will provide data for a sizeable fraction of the observable sky. This rich data set should provide the means to answer fundamental questions: what are the laws of physics at high energies in the Early Universe? What is the nature of neutrinos? What is dark matter? What is dark energy? Why are there baryons at all? In this talk I will review the current status, provide a roadmap for future prospects and discuss in detail how we might approach the task of extracting information from the sky to answer the above questions.

Of Bodies Changed to New Forms – Tim Atherton Thu. April 21st, 2016
4:15 pm-5:15 pm

Soft matter is a broad class of materials with many examples found in everyday life: foods, crude oil, many biological materials, granular materials, liquid crystals, plastics. All of these are unified by the property that they’re readily deformable because the elastic energy is of the same order of magnitude as the ambient thermal energy. Moreover, they spontaneously assemble into richly ordered structures that respond to many different kinds of external stimuli. Soft materials are therefore ideal candidates for advanced engineering applications including soft, biomimetic robots, self-building machines, shape-shifters, artificial muscles, new high-performance all-optical switches and chemical delivery packages. In each of these,

New Directions in Bouncing Cosmologies – Anna M. Ijjas Tue. April 19th, 2016
11:30 am-12:30 pm

In this talk, I will discuss novel ideas to smooth and flatten the universe and generate nearly scale-invariant perturbations during a contracting phase that precedes a cosmological bounce. I will also present some recent work on the possibility of having well-behaved non-singular bounces.

The 17 Position Knob: Tuning Interactions With Rare Earths – Paul C. Canfield Mon. April 18th, 2016
12:30 pm-1:30 pm

Physicists see the rare earth group of elements as a powerful tool for tuning the properties of materials. Choice or control of rare earths can be used to modify (i) the size of the unit cell, (ii) the size of the local moment and degree of coupling, (iii) the size and direction of magnetic anisotropy, (iv) the amount of entropy that can be removed at low temperatures, (v) the degree of band filling, and / or (vi) the degree of hybridization. In this seminar I will provide an overview and examples of how this region of the periodic table can be used to guide and inspire research into a wide swath of novel materials and ground states.

Resonant Tunneling in a Dissipative Environment: Quantum Critical Behavior – Harold Baranger Thu. April 14th, 2016
4:15 pm-5:15 pm
The role of the surroundings, or environment, in quantum mechanics has long captivated physicists’ attention. Recently, quantum phase transitions (QPT)– a qualitative change in the ground state as a function of a parameter– have been shown to occur in systems coupled to a dissipative environment. Despite the ubiquity of QPTs in contemporary theoretical physics, obtaining clear experimental signatures has been challenging. I start by presenting a recent experiment in which it was possible to thoroughly characterize a QPT caused by coupling to an environment. The system is a single-molecule transistor built from a carbon nanotube quantum dot connected to strongly dissipative contacts.
Mapping the Phase Diagram of a One-Dimensional Topological Superconductor – Sergey Frolov Mon. April 11th, 2016
12:30 pm-1:30 pm

Download the abstract Tunneling spectroscopy measurements on one-dimensional superconducting hybrid materials have revealed signatures of Majorana fermions which are the edge states of a bulk topological superconducting phase. We couple strong spin-orbit semiconductor InSb nanowires to conventional NbTiN superconductors to obtain additional signatures of Majorana fermions and to explore the magnetic-field driven topological phase transition. With improved device fabrication, namely more transparent contacts to superconductors and stronger coupled gate electrodes, we are mapping out the phase diagram of the topological phase in the space of Zeeman energy and chemical potential, and investigating the apparent closing and re-opening of the superconducting gap.

Can Charge Qubits Compete with Spin Qubits for Quantum Information Processing? – HongWen Jiang Thu. April 7th, 2016
4:15 pm-5:15 pm

onductor quantum dots (QDs) are a leading approach for the implementation of solid-state based qubits. In principle, either charge or spin can be used to encode a qubit. However, in the last ten years or so, a disproportionally large quantity of research has been devoted to spin qubits, mainly because of the relatively long single-qubit dephasing times for spin qubits. In this talk I present a sequence of experimental results on QD based charge qubits, demonstrating both one-qubit [1] and two-qubit [2] quantum logic operations. The finding of this research appears to go against the conventional wisdom that charge qubits are inferior in comparison to spin qubits for semiconducting materials.

Beyond Precision Cosmology – Licia Verde Tue. April 5th, 2016
11:30 am-12:30 pm

The avalanche of data over the past 10-20 years has propelled cosmology into the “precision era”. The next challenge cosmology has to meet is to enter the era of accuracy. Because of the intrinsic nature of studying the Cosmos and the sheer amount of data available and coming, the only way to meet these challenges is by developing suitable and specific statistical techniques. The road from precision Cosmology to accurate Cosmology goes through statistical Cosmology. I will outline some open challenges and discuss some specific examples.

Nanoscopic Manipulation and Nanoimaging of Liquid Crystals – Charles Rosenblatt Mon. April 4th, 2016
12:30 pm-1:30 pm

Liquid crystals present a remarkable array of fascinating physical phenomena, and are now a >200 billion dollar world-wide industry. As liquid crystals most often are housed in a closed cell or sit atop a substrate, the treatment of the substrate plays a pivotal role. For the past fifteen years we have developed and exploited scanning probe microscope techniques to manipulate the liquid crystal’s orientation and order parameter at a surface on length scales down to a few tens of nanometers, and performed optical imaging with volumetric resolution 1000 times better than confocal microscopy. In this talk I will present our experimental techniques at the nanoscale,

Nanoscopic Manipulation and Nanoimaging of Liquid Crystals – Charles Rosenblatt Mon. April 4th, 2016
12:30 pm-1:30 pm

Liquid crystals present a remarkable array of fascinating physical phenomena, and are now a >200 billion dollar world-wide industry. As liquid crystals most often are housed in a closed cell or sit atop a substrate, the treatment of the substrate plays a pivotal role. For the past fifteen years we have developed and exploited scanning probe microscope techniques to manipulate the liquid crystal’s orientation and order parameter at a surface on length scales down to a few tens of nanometers, and performed optical imaging with volumetric resolution 1000 times better than confocal microscopy. In this talk I will present our experimental techniques at the nanoscale,

Controlling Coherent Spins at the Nanoscale: Prospects for Practical Spin-Based Technology – Jesse Berezovsky Thu. March 31st, 2016
4:15 pm-5:15 pm

Despite living in a complex, room temperature, solid-state environment, the spin of electrons bound to a nitrogen-vacancy (NV) defect in diamond can exist in a delicate quantum superposition over relatively long timescales. The delicacy of this state makes the system exquisitely sensitive to perturbations in magnetic field, temperature, or strain. As such, the NV is a good candidate for sensing applications, providing precise measurements with sub-nanometer spatial resolution. The robust quantum coherence of the NV spin also suggests applications in quantum information processing: if we can engineer entangled states of many NV spins, then computation may be carried out in the unbelievably voluminous Hilbert space of this system,

New Approaches to Dark Matter – Justin Khoury Tue. March 29th, 2016
11:30 am-12:30 pm

In this talk I will discuss a novel theory of superfluid dark matter. The scenario matches the predictions of the LambdaCDM model on cosmological scales while simultaneously reproducing the MOdified Newtonian Dynamics (MOND) empirical success on galactic scales. The dark matter and MOND components have a common origin, as different phases of a single underlying substance. This is achieved through the rich and well-studied physics of superfluidity. The framework naturally distinguishes between galaxies (where MOND is successful) and galaxy clusters (where MOND is not): due to the higher velocity dispersion in clusters, and correspondingly higher temperature, the DM in clusters is either in a mixture of superfluid and normal phases,

Nanomaterials in Liquid Crystal Mediated Interactions – Rajratan Basu Mon. March 28th, 2016
4:00 pm-5:00 pm

In liquid crystals (LC) the effect of nonmesogenic guest-nanoparticles on the LC’s bulk properties often rests on the molecular identification at the nanoscale in order to share and disseminate the `information’ coded into the nanostructure of the nanoparticles. I will present two types of nanomaterials and their intriguing interactions with LCs. Graphene is a twodimensional crystalline carbon allotrope where carbon atoms are densely packed in a regular sp2- bonded atomic-scale hexagonal pattern. This graphene nanostructure can used to enhance the tilted smectic-C order in an LC, giving rise to a faster ferroelectric switching. The presence of graphene can improve the electro-optic response and decrease the rotational viscosity of an LC.

Photophysics of Organic Materials: From Thin-Film Devices to Single Molecules and from Optoelectronics to Entomology – Oksana Ostroverkhova Thu. March 24th, 2016
4:15 pm-5:15 pm

Organic (opto)electronic materials have been explored in a variety of applications in electronics and photonics. They offer several advantages over traditional silicon technology, including low-cost processing, fabrication of large-area flexible devices, and widely tunable properties through functionalization of the molecules. Over the past decade, remarkable progress in the material design has been made, which led to a considerable boost in performance of organic thin-film transistors, solar cells, and other applications that rely on (photo)conductive properties of the material. Nevertheless, the nature of photoexcitations, charge carrier photogeneration, and transport in organic semiconductors is not completely understood. In this presentation, I will summarize our efforts towards understanding photoinduced charge carrier dynamics in high-performance organic materials and towards development of novel,

Calibration of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) Detectors – Madeline Wade Tue. March 22nd, 2016
11:30 am-12:30 pm

Calibration is the critical link between the LIGO detectors and searches for gravitational-wave signals in LIGO data. The LIGO calibration effort involves constructing the external strain incident on each LIGO detector from the digitized readout of the LIGO photodetectors. The essential steps in calibration are the development of accurate models of the LIGO detectors, the digitization of these models, and the application of the calibration models to construct the external strain. The Advanced LIGO era has brought new complexities in accurately modeling the LIGO detectors as well as the challenge of producing calibrated external strain data in low-latency. This talk will give an overview of the Advanced LIGO calibration procedure,

New Probes of Large-scale CMB Anomalies – Simone Aiola Tue. March 15th, 2016
11:30 am-12:30 pm

Inflation prescribes a homogenous and isotropic universe on large scales, and it generates density fluctuations which are expected to be spatially correlated over the whole Hubble volume. Such fundamental predictions have been tested with current Cosmic Microwave Background (CMB) data and found to be in tension with our — remarkably simple — ΛCDM model. Is it just a random fluke or a fundamental issue with the present model? In this talk, I will present new possibilities of using CMB polarization as a probe of the measured suppression of the large-scale temperature correlation function. I will also discuss the viability of using this new technique with present and upcoming data.

APS March Meeting Mon. March 14th, 2016
12:30 pm-1:30 pm
Preview APS March Meeting Talks – Graduate Students Thu. March 10th, 2016
11:00 am-12:00 pm

Sukrit Sucharitacul, Few-layer III-VI and IV-VI 2D semiconductor transistorsShuhao Liu, Imaging the long diffusion lengths of photo-generated carriers in mixed halide perovskite films

Shuhao Liu, Imaging the long diffusion lengths of photo-generated carriers in mixed halide perovskite films Robert Badea, Magneto-optical mapping of the domain wall pinning potential in ferromagnetic films

Robert Badea, Magneto-optical mapping of the domain wall pinning potential in ferromagnetic films Michael Wolf, Coupling a driven magnetic vortex to individual nitrogen-vacancy spins for fast, nanoscale addressability and coherent manipulation

Michael Wolf, Coupling a driven magnetic vortex to individual nitrogen-vacancy spins for fast,

FMR-Drive Pure Spin Transport in Metals and Magnetic Insulators – Fengyuan Yang Mon. March 7th, 2016
12:30 pm-1:30 pm

Spintronics relies on the generation, transmission, manipulation, and detection of spin current mediated by itinerant charges or magnetic excitations. Ferromagnetic resonance (FMR) spin pumping is a powerful technique in understanding pure spin current. Building on the highquality Y3Fe5O12 (YIG) films grown by our sputtering technique and the large inverse spin Hall effect (ISHE) signals enabled by these films, we have characterized pure spin currents in several classes of materials with different magnetic structures, including: nonmagnetic (NM) metals, ferromagnetic (FM) metals, nonmagnetic insulators, and antiferromagnetic (AF) insulators. The spin Hall angles determined for a series of 3d, 4d, and 5d NM metals show that both atomic number and d-electron count play important roles in spin Hall physics.

Joining Forces Against the Dark Side of the Universe: The Cosmic Microwave Background and the Large Scale Structure – Shirley Ho Fri. March 4th, 2016
12:30 pm-1:30 pm

Despite tremendous recent progress, gaps remain in our knowledge of our understanding of the Universe. For example, we have yet pinned down the properties of dark energy, nor have we confirmed Einstein’s theory of Gravity at the largest scales. Current and upcoming large sky surveys of the cosmic microwave background, large scale structure in galaxies, quasars, lyman-alpha forest and 21cm presents us with the best opportunity to understand various mysterious properties of the Universe and its underlying principles. I will review recent results from the Baryon Oscillations Spectroscopic Survey (BOSS). These results have demonstrated the feasibility of high precision Baryon Acoustic Oscillation (BAO) measurement,

Gravitational Waves Discovered: The Recent Detection of an Ancient Binary Black Hole Merger – Leslie E. Wade Thu. March 3rd, 2016
4:15 pm-5:15 pm

On September 14, 2015 the two ground-based interferometers that comprise the LIGO network directly observed the gravitational-wave signature of a 1.3 billion-year-old binary black hole merger. This incredible discovery is not only the first direct detection of gravitational waves, which cements Einstein’s prediction of their existence, it is also the first ever observation of two black holes merging. Between the time of the detection and the time of the public announcement, the activity of the LIGO Scientific Collaboration was shrouded in secrecy in an effort to squash any premature rumors and conduct a thorough, unbiased analysis of the validity of this incredible finding.

Tailored Radiative Processes of Quantum Dots and 2D Materials – Maiken H. Mikkelsen Mon. February 29th, 2016
4:00 pm-5:00 pm

Metal-dielectric nanocavities have the ability to tightly confine light to small mode volumes resulting in strongly increased local density of states. Placing fluorescing molecules or semiconductor materials in this region enables wide control of radiative processes including absorption and spontaneous emission rates, quantum efficiency, and emission directionality. In this talk, I will describe our recent experiments utilizing a tunable plasmonic platform where emitters are sandwiched in a sub-10-nm gap between colloidally synthesized silver nanocubes and a metal film. Utilizing dye molecules with an intrinsic long lifetime reveals spontaneous emission rate enhancements exceeding a factor of 1,000 while maintaining directional emission and high quantum efficiency [Akselrod et al.

Aspects of Photonic Topological Insulators – Mikael Rechtsman Mon. February 22nd, 2016
12:30 pm-1:30 pm

I will present the observation of the topological protection of light – specifically, a photonic Floquet topological insulator. Topological insulators (TIs) are solid-state materials that are insulators in the bulk, but conduct electricity along their surfaces – and are intrinsically robust to disorder. In particular, when a surface electron in a TI encounters a defect, it simply goes around it without scattering, always exhibiting – quite strikingly – perfect transmission. The structure is an array of coupled helical waveguides (the helicity generates a fictitious circularly-polarized electric field that leads to the TI behavior), and light propagating through it is ‘topologically protected’

Non-Linear Optics of Ultrastrongly Coupled Cavity Polaritons – Mike Crescimanno Thu. February 18th, 2016
4:15 pm-5:15 pm

Recent experiments at CWRU (Singer) have developed organic cavity polaritons that display world-record vacuum Rabi splittings of more than an eV.‭ ‬This ultrastrongly coupled polaritonic matter is a new regime for exploring non-linear optical effects.‭ ‬After an introduction to polariton physics, we‭ apply quantum optics theory to quantitatively determine various non-linear optical effects including types of‭ ‬low harmonic generation‭ (‬SHG and THG‭) ‬in single and double cavity polariton systems. We also point out potentially interesting physical questions/interpretations that this study raises. Ultrastrongly coupled photon-matter systems such as these may be the foundation for technologies including low-power optical switching and computing.

Albert Michelson, the Michelson-Morley experiment, and the dichotomy between megaprojects and table-top science – Philip Taylor Thu. February 11th, 2016
4:15 pm-5:15 pm

During the past 130 years the range of sizes and costs for scientific apparatus has expanded enormously. While some groundbreaking science is still done at modest cost, other experiments now require several billions of dollars to achieve their goals. A description of some significant milestones in the career of Albert Abraham Michelson illustrates how in this one individual’s life this divergence may have had its first exemplar, as his vision expanded beyond the exquisitely precise interferometer used in the Michelson-Morley experiment to the mile-long vacuum tube used in his later measurements of the speed of light.

Testing Early Universe Physics with Upcoming Observations – Emanuela Dimastrogiovanni Wed. February 10th, 2016
12:30 pm-1:30 pm

Cosmology has seen tremendous progress thanks to precision measurements and is bound to greatly benefit from upcoming Large Scale Structure and Cosmic Microwave Background data. I will point out a number of interesting directions. In particular, I discuss how the microphysics of inflation may be tested in galaxy surveys through “fossil” signatures originating from squeezed primordial correlations. I further elaborate on the constraining power of CMB spectral distortions on small-scale cosmological fluctuations and on particle decays in the very early Universe in relation to reheating. I also describe some of the possible constraints on inflation and reheating from future B-mode observations.

New Paradigm for Physics Beyond the Standard Model – Pavel Fileviez Perez Tue. February 9th, 2016
11:30 am-12:30 pm

The great desert hypothesis in particle physics defines the relation between the electroweak scale and the high scale where an unified theory could describes physics. In this talk we review the desert hypothesis and discuss the main experimental constraints from rare decays. We present a new class of theories for the TeV scale where the desert hypothesis is not needed. In this context one predicts the existence of new particles with baryon and lepton numbers called lepto-baryons. The implications for cosmology, collider experiments and the unification of forces are discussed.

Cosmology from the Megaparsec to the Micron – Amol Upadhye Fri. February 5th, 2016
12:30 pm-1:30 pm

Two major challenges for cosmology over the next decade are to characterize the dark energy responsible for the cosmic acceleration and to weigh the neutrinos, the only Standard Model particles whose masses are not yet known. Part I of the presentation describes my ongoing work to understand the effects of massive neutrinos and evolving dark energy on the formation of large-scale structure. I include both effects in a redshift-space generalization of Time-RG perturbation theory, and establish its validity through comparison to N-body simulations. In Part II I discuss my previous work using stars and laboratory experiments to search for couplings between dark energy and Standard Model particles.

A New Twist on Electromagnetism for Energy Conversion – Stephen Rand Thu. February 4th, 2016
4:15 pm-5:15 pm

In electromagnetism effects of the magnetic field are generally ignored. However in recent optical experiments intense magnetic light scattering has been observed as the result of a dynamic magneto-electric interaction that transcends the bounds of the multipole expansion through magnetic torque due to the Lorentz force. The implications of this fundamental discovery for intense magnetic interactions in natural materials and the conversion of solar energy to electricity with negligible heat generation will be discussed.

Massive and Partially Massless Gravity and Higher spins – Kurt Hinterbichler Tue. February 2nd, 2016
11:30 am-12:30 pm

On de Sitter space, there exists a special value for the mass of a graviton for which the linear theory propagates 4 rather than 5 degrees of freedom, known as a partially massless graviton. If a satisfactory non-linear version of the theory can be found and coupled to known matter, it would have interesting properties and could solve the cosmological constant problem. I will review attempts at constructing such a theory and some no-go’s, and will describe a Vasiliev-like theory containing a tower of partially massless higher spins.

Combined First-Principles Molecular Dynamics / Density-Functional Theory Study of Ammonia Oxidation on Pt(100) Electrode – Dmitry Skachkov Mon. February 1st, 2016
12:30 pm-1:30 pm

A combined first-principles molecular dynamics/density functional theory study of the electrooxidation of ammonia is conducted to gain an atomic-level understanding of the electrocatalytic processes at the Pt(1 0 0)/alkaline solution interface and to probe the mechanistic details of ammonia electrooxidation on the metal surface. A systematic study of adsorption and relative stability of ammonia and the intermediate species on the Pt(1 0 0) surface as a function of potential is carried out and activation energy profiles for the mechanistic steps in the ammonia oxidation are presented. The reaction mechanism is potential dependent: the modeling study supports the Oswin and Salomon’s mechanism for moderate surface potentials (≥ +0.5 V vs.

The 2015 Science Nobel Prizes – What were they given for? – Kurt Runge (Chemistry), Jim Kazura (Physiology or Medecine), Andrew Tolley (Physics) Thu. January 28th, 2016
4:15 pm-5:15 pm
Testing Eternal Inflation – Matthew Johnson Tue. December 8th, 2015
11:30 am-12:30 pm

The theory of eternal inflation in an inflaton potential with multiple vacua predicts that our universe is one of many bubble universes nucleating and growing inside an ever-expanding false vacuum. The collision of our bubble with another could provide an important observational signature to test this scenario. In this talk I will summarize recent work providing a quantitative connection between the scalar field lagrangian underlying eternal inflation and the observational signature of bubble collisions. I will also summarize existing constraints and forecasts for future searches using CMB and LSS, as well as discuss the general relevance of this work for assessing fine-tuning problems in inflationary cosmology.

Bigravity: Dead or Alive? – Adam Solomon Tue. December 1st, 2015
11:30 am-12:30 pm

Spurred in large part by the discovery of the accelerating universe, recent years have seen tremendous advances in our understanding of alternatives to general relativity, particularly in the large-distance and low-curvature régimes. Looming large in this field is the recent development of a ghost-free, nonlinear theory of massive gravity and multimetric gravity (or equivalently, theories of interacting gravitons), which had proven elusive for the better part of seven decades. Nevertheless, both massive gravity and its generalization to a bimetric theory have run into potentially-deadly problems in the search for viable, self-accelerated cosmologies. I will summarize some of these issues, and then discuss possible ways out.

Non-adiabatic Transport in Single-Electron Transistors in the Kondo Regime – Andrei Kogan Mon. November 23rd, 2015
12:30 pm-1:30 pm

Magnetic impurities in conductors alter the Fermi sea: A many-body state (A Kondo singlet) is formed that entangles itinerant carriers and the impurity site. This causes a sharp rearrangement of the density of states near the Fermi surface into a hierarchical set governed by a single energy parameter Tk, the Kondo temperature. Equilibrium physics of such electronic “knots” scales with Tk and is highly universal: impurities that differ microscopically from one another yet have similar Kondo temperatures produce Kondo states with similar properties. Recent studies of Kondo physics with voltage-controllable spin traps known as Single-Electron Transistors (SETs) have focused on nonequiibrium Kondo phenomena,

Gravitational wave detection with precision interferometry – Nergis Malvalvala (unofficial colloquium) Fri. November 20th, 2015
10:15 am-11:15 am

Laser interferometer gravitational wave detectors are poised to launch a new era of gravitational wave astronomy and unprecedented tests of general relativity. I will describe experimental efforts worldwide to detect gravitational waves, and the progress to date. The limits to the sensitivity of the present generation of interferometric gravitational wave detectors and the path to higher sensitivity future gravitational wave detectors will be discussed.

Chip-integrated Nanophotonic Structures for Classical and Quantum Devices – Antonio Badolato Mon. November 16th, 2015
12:30 pm-1:30 pm

Chip-integrated nanophotonics investigates the interaction of light with nanostructures integrated on a chip. Lying at the intersection of condensed matter physics, optics, nanotechnology, and materials science, nanophotonics draws upon expertise from broad areas of physics and engineering, while presenting major opportunities to advance fundamental physics and transformative photonic technologies. In this talk, I will focus on our experimental research in two areas of nanophotonics. First, I will show that nanostructured semiconductors, such as quantum dot heterostructures coupled to photonic crystal nanocavities, can now offer

First, I will show that nanostructured semiconductors, such as quantum dot heterostructures coupled to photonic crystal nanocavities,

Ultra-low field MRI – Michael Hatridge Fri. November 13th, 2015
12:30 pm-1:30 pm

Superconducting Quantum Interference Devices (SQUIDs), consisting of two Josephson junctions in a closed superconducting loop, are exquisitely sensitive detectors of magnetic flux. In recent years, we have built magnetic resonance imaging (MRI) scanners based around these detectors which are capable of in vivo imaging at ultra-low (132 microTesla) fields, rather than the several Tesla of conventional MRI. I’ll discuss the challenges and unique advantages of ultra-low field MRI, including enhanced contrast between tissues types such as normal and cancerous prostate tissue which are nearly identical at high fields.

Remote entanglement in superconducting quantum information – Michael Hatridge Thu. November 12th, 2015
4:15 pm-5:15 pm

I’ll review material from the technical lectures and discuss the difference between entanglement via local and ‘remote’ interactions. I’ll discuss possible methods for constructing remote entangling measurements in superconducting quantum information and detail our experimental efforts to remotely entangle qubits via simultaneous readout and phase-preserving amplification.

Remote entanglement in superconducting quantum information – Michael Hatridge Thu. November 12th, 2015
4:15 pm-5:15 pm

I’ll review material from the technical lectures and discuss the difference between entanglement via local and ‘remote’ interactions. I’ll discuss possible methods for constructing remote entangling measurements in superconducting quantum information and detail our experimental efforts to remotely entangle qubits via simultaneous readout and phase-preserving amplification.

Josephson junctions and quantum microwave circuits 2: amplifiers – Michael Hatridge Tue. November 10th, 2015
11:30 am-12:30 pm

Here we will take the concepts from lecture one and set out to construct from the same Josephson junctions very weakly non-linear circuits which operate as phase-preserving amplifiers. I’ll discuss some of the numerous chall enges in designing superconducting amplifiers which are robust and simple while achieving nearly ideal performance. I’ll also discuss the quantum-limit of amplification, how closely we can approach it, and how such amplifiers allow precision readout of our quantum bits.

Michelson Postdoc Lecture – Michael Hatridge Mon. November 9th, 2015
12:30 pm-1:30 pm
Josephson junctions and quantum microwave circuits 1: qubits and cavities – Michael Hatridge Mon. November 9th, 2015
12:30 pm-1:30 pm

In this lecture I’ll review the basics of the Josephson junction and how it is used as the key building block in superconducting quantum information. I’ll show how we build coupled circuits consisting of a rather non-linear oscillator (which we use as our qubit) coupled to an (almost) linear oscillator/cavity which both shelters the qubit from the outside environment and allows for qubit control and quantum-non-demolition readout.

Intracellular Pressure Dynamics in Cells – Wanda Strychalski Thu. November 5th, 2015
4:15 pm-5:15 pm

Cell migration plays an essential role in many important biological processes such as wound healing, cancer metastasis, embryonic development, and the immune response. Recent advances in microscopy have led to an increasing number of qualitative observations of cell migration in 3D environments that closely mimic physiological conditions. In particular, they showed that some cells such as leukocytes, embryonic cells, and cancer cells, migrating through 3D matrices adopt an amoeboid phenotype characterized by round, liquid-filled, pressure-driven protrusions. Blebs are one type of protrusion these cells use to migrate in different environments. Recent experiments involving blebbing cells have led to conflicting hypotheses regarding intracellular pressure dynamics.

Supercooling-Driven Glass Behaviour in Systems Exhibiting Continuous Symmetry Breaking – Sami Kralj Wed. November 4th, 2015
12:30 pm-1:30 pm

Symmetry breaking is ubiquitous in nature and represents the key mechanism behind rich diversity of patterns exhibited by nature. One commonly introduces an order parameter field to describe onset of qualitatively new ordering in a system on varying a relevant control parameter driving a symmetry breaking transition. In case of continuous symmetry breaking an order parameter consists of two qualitatively different components: an amplitude and gauge field. The latter component enables energy degeneracy and reveals how symmetry is broken. Inherent degeneracy could in general lead to nearby regions exhibiting significantly different gauge fields. Resulting frustrations can nucleate topological defects (TDs) [1].

Enabling High Performance Computational Physics with Community Libraries – Matt Knepley Thu. October 29th, 2015
4:15 pm-5:15 pm

I will speak about the PETSc library, a community effort that I help lead, which provides scalable parallel linear and nonlinear algebraic solvers. It is very often used to solve complex, multiphysics problems arising from PDEs, and I will show examples from geophysics, fluid dynamics, electrostatics, neutronics, fracture mechanics, and molecular biology.

Bi-gravity from DGP Two-brane Model – Yasuho Yamashita Wed. October 28th, 2015
12:30 pm-1:30 pm

We discuss whether or not bigravity theory can be embedded into the braneworld setup. As a candidate, we consider Dvali-Gabadadze-Porrati two-brane model. We will show that we can construct a ghost free model whose low energy spectrum is composed of a massless graviton and a massive graviton with a small mass, fixing the brane separation with the Goldberger-Wise radion stabilization. We also show that there is two branches: the normal branch is stable and the self-accelerating branch is inevitably unstable, and discuss the condition for the normal branch. Next, we consider DGP two-brane model without the radion stabilization to discuss how the ghost free bigravity coupled with a single scalar field can be derived from a braneworld setup.

The Instability of de Sitter Space and Dynamical Dark Energy: Massless Degrees of Freedom from the Conformal Anomaly in Cosmology – Emil Mottola Tue. October 27th, 2015
11:30 am-12:30 pm

Global de Sitter space is unstable to particle creation, even for a massive free field theory with no self-interactions. The Bunch-Davies state is a definite phase coherent superposition of particle and anti-particle solutions in both the asymptotic past and future, and therefore is not a true vacuum state. In the closely related case of particle creation by a constant, uniform electric field, a time symmetric state analogous to the de Sitter invariant one is constructed, which is also not a stable vacuum state. The conformal anomaly plays a decisive role in the growth of perturbations and de Sitter symmetry breaking.

Photogeneration and Charge Transport in Liquid Crystalline Organic Semiconductors – Sanjoy Paul Mon. October 26th, 2015
12:30 pm-1:30 pm

Organic semiconductors (OSCs) are emerging candidates for the applications in electronic and photonic devices due to material’s low cost and ease of processing. Many materials have been studied to understand the charge generation and transport physics, as well as to develop techniques for facile processing into light emitting diodes, thin film transistors, photovoltaics, and host of other devices. A recurring theme in this effort is the role of disorder in determining critical material parameters, such as mobility and photogeneration efficiency. A particularly useful class of materials in this quest is that of liquid crystalline (LC) OSCs. LCOSCs offer many advantages including facile alignment and the opportunity to study the effects of differing intermolecular geometries on transfer integrals,

Quantum Chromodynamics at Five Trillion Degrees Kelvin – Michael Strickland Thu. October 22nd, 2015
4:15 pm-5:15 pm

Relativistic heavy ion collision experiments at Brookhaven National Laboratory and at CERN have made it possible to turn back the clock to approximately one-millionth of a second after the big bang; a time when matter, as we know it, did not exist. At these early times, the temperature of the universe was on the order of 10^12 Kelvin and the protons and neutrons, which now constitute atomic nuclei, had not yet been formed. Instead, the universe was a super hot plasma of quarks and gluons called the quark gluon plasma (QGP). In this colloquium I will review the theoretical tools necessary to understand the quark gluon plasma in the early universe and formed in relativistic heavy-ion collisions.

Spins in 2D Materials – Roland Kawakami Mon. October 19th, 2015
12:30 pm-1:30 pm

Two-dimensional crystals such as graphene and monolayer transition metal dichalcogenides (TMD) possess unique properties not found in bulk materials. These materials are atomically-thin, yet are strong enough to remain intact as free standing membranes. Because these materials are “all surface”, they tend to be highly surface sensitive and amenable to inducing proximity effects. In this talk, I will discuss our progress of investigating spin-dependent phenomena in graphene and TMD monolayers. We investigate spin transport in graphene utilizing ferromagnetic electrodes to inject and detect

In this talk, I will discuss our progress of investigating spin-dependent phenomena in graphene and TMD monolayers.

In honor of Ben Segall’s 90th birthday – Arnold Dahm, Philip Taylor, Walter Lambrecht Thu. October 15th, 2015
4:15 pm-5:15 pm

Following brief reminiscences by Arnie Dahm and Phil Taylor, Walter Lambrecht will review some of Ben Segall’s early papers on the electronic band structure and optical properties of semiconductors. He will tell us what these papers were about, and place them in the context of the time. He will then relate how these topics evolved to the present day and describe the impact they had over the years.

A reception will follow in Tomlinson Hall lobby.

Perspectives on WIMP Dark Matter – Pearl Sandick Tue. October 13th, 2015
11:30 am-12:30 pm

The question of the identity of dark matter remains one of the most important outstanding puzzles in modern physics. Weakly Interacting Massive Particles (WIMPs) have long been the frontrunner dark matter candidate, with the supersymmetric neutralino serving as the canonical WIMP. In this talk, I’ll discuss recent results relevant to the search for dark matter, supersymmetric and otherwise, and highlight the spectrum of theoretical and phenomenological approaches to its study. From fundamental constructions to simplified models and effective theories, each approach plays a specific role in furthering our understanding and allowing us to evaluate the prospects for discovery of dark matter.

Static and Dynamic Flowers in Strained Graphene – Nancy Sandler Mon. October 12th, 2015
12:30 pm-1:30 pm

The coupling of geometrical and electronic properties is a promising venue to engineer conduction properties in graphene. In particular, different regimes can be achieved by manipulating confinement and strain fields, as shown in recent experiments on nanobubbles, drumheads oscillating membranes, and narrow strips deposited on patterned SiC substrates [1].

To investigate strain signatures on graphene systems, we focus on a simple model with a circularly symmetric out-of-plane deformation. Results from numerical tight-binding and Dirac-continuum models for a static deformation reveal intriguing flower-shaped structures in the local density of states with profound consequences for charge transport through the structure [2].

The Standard Model of Particle Physics via Non-Commutative Geometry – Latham Boyle Fri. October 9th, 2015
12:30 pm-1:30 pm

I will introduce Connes’ notion of non-commutative geometry, and explain how it offers a novel geometric perspective on certain otherwise unexplained features of the standard model of particle physics, and a more restrictive framework than effective field theory for exploring physics beyond the standard model. I will also explain the main ideas behind a new reformulation of NCG which has certain key mathematical and physical advantages over Connes’ traditional “spectral triple” formulation. In this reformulation, the traditional NCG axioms are considerably simplified and unified; a number of problematic issues in the traditional NCG construction of the standard model are fixed;

The Status and Challenges of Lead Halide Perovskite Solar Cells – Yanfa Yan Mon. October 5th, 2015
12:30 pm-1:30 pm

Organic-inorganic methylammounium lead halide perovskites, CH3NH3PbX3 (X= Cl, Br, I), have revolutionized the field of thin-film solar cells. Within five years, the efficiency of lead halide perovskite-based thin-film solar cells have increased rapidly from 3.8% in 2009 to 20.1% for a planar CH3NH3PbI3-based thin-film solar cell in 2014. Such rapid progress has never been seen before in the history of solar cell development. In this talk, I will review the history and status of lead halide perovskite thin films solar cells. I will explain why lead halide perovskites exhibit superior photovoltaic properties that conventional solar cell materials such as Si,

The Conformal Bootstrap: From Magnets to Boiling Water – David Simmons-Duffin Thu. October 1st, 2015
4:15 pm-5:15 pm

Conformal Field Theory (CFT) describes the long-distance dynamics of numerous quantum and statistical many-body systems. The long-distance limit of a many-body system is often so complicated that it is hard to do precise calculations. However, powerful new techniques for understanding CFTs have emerged in the last few years, based on the idea of the Conformal Bootstrap. I will explain how the Bootstrap lets us calculate critical exponents in the 3d Ising Model to world-record precision, how it explains striking relations between magnets and boiling water, and how it can be applied to questions across theoretical physics.

An Anisotropic Universe Due to Dimension-changing False Vacuum Decay – James Scargill Tue. September 29th, 2015
11:30 am-12:30 pm

In this talk I will consider the observational consequences of models of inflation after false vacuum decay in which the parent vacuum has a smaller number of large dimensions than our current vacuum. After introducing and briefly discussing in general the topic of inflation after false vacuum, I will then explain how such events can occur which change the number of large dimensions and lead to an anisotropic universe. The effects on the CMB of anisotropy at late times might be expected to render irrelevant the effects of primordial anisotropy, however after showing how to properly deal with the latter I will demonstrate how for the tensor perturbation modes the primordial effects are much larger than expected and can in fact be dominant.

Device-compatible Defect Engineering of Rare Earth Doped Nitrides – Volkmar Dierolf Mon. September 28th, 2015
12:30 pm-1:30 pm

LED-lighting is at the verge of replacing conventional incandescent light sources. These white LEDs are based on nitride technology which produces the blue emission, that is subsequently converted in a separate phosphorescent layer to provide the additional required colors. The latter often consists of an insulating material doped with rare earth ions. In order to facilitate further integration, the possibility of introducing rare earth ions directly into the nitride material has been explored, with considerable success. Doping with europium ions (Eu) is of particular interest since they can produce the red color, which remains a challenge for nitride based materials.

Who and where is the graviton? – Claudia de Rham Thu. September 24th, 2015
4:15 pm-5:15 pm

One hundred years after “Die Feldgleichungen der Gravitation” by Albert Einstein (The Fields Equations of Gravitation) and perhaps at the eve of direct gravitational detection, the time is right to pause and ponder about the nature of the particle carrier of the gravitational force: the graviton. To unify the theory of gravity with the other forces of nature we expect the theory of General Relativity to be modified at small distances. Could it be that General Relativity is also modified at large distances as large as our current observable Universe ? This may depend on the very nature of the graviton.

Prospects for Measuring the Neutron-star Equation of State with Advanced Gravitational-wave Detectors – Leslie Wade Tue. September 22nd, 2015
11:30 am-12:30 pm

It is widely anticipated that the first direct detections of gravitational waves will be made by advanced gravitational-wave detectors, such as the two Laser Interferometer Gravitational-wave Observatories (LIGO) and the Virgo interferometer. Arguably the most important source for ground-based interferometers are coalescing binary neutron stars. Following the detection of such a system, a more detailed followup analysis will seek to measure certain properties of the component neutron stars, such as their masses and/or spin configurations. In particular, it has been shown that the gravitational waves emitted by binary neutron stars carry information about the neutron-star equation of state. In this talk,

Quantum Magnetism in Low Dimensions: An Intriguing Phenomenon Connecting Biology with Physics – Yi-Kuo Yu Mon. September 14th, 2015
12:30 pm-1:30 pm

Magnetism is an important problem in many areas of science including biology, physics and material science. For example, many migratory animals (birds, whales and sea turtles) use magnetism to sense direction for their migrations; computer hard drives store information via magnetism; and so forth. Quantum magnetism in low-dimensional systems plays a particularly important role in biophysical systems within which magnetic moments of different sizes might be useful for different purposes. In this perspective, the role of magnetism with higher magnetic moments is relatively less understood.
To gain a better understanding for magnetism encompassing low and high moments, we studied a quantum mechanical spin lattice system consisting of one-dimensional anti-ferromagnetic Heisenberg chain of spin s embedded in a three dimensional lattice.

The Science of Climate Change and the Changing Climate of Science – Philip Taylor Thu. September 10th, 2015
4:15 pm-5:15 pm

Isn’t science supposed to be a field of study in which everybody eventually agrees on what is correct and what is mistaken? Yes, it is, but do we agree on how long it will be before “eventually” happens, especially when $5,000,000,000,000 per annum depends on whose science is correct? Probably not. The American Physical Society is laboring mightily on a new version of its 2007 Climate Change Statement, but seems likely to give birth to a mouse. How did it happen that both Pope Francis (“Obstructionist attitudes, even on the part of believers, can range from denial of the problem to indifference”) and Islamic leaders (“The present climate change catastrophe is a result of the human disruption of this balance”) seem to have a better grasp of the problem than our beloved APS?

Buckling Instabilities and Recoil Dynamics in Free-Standing Liquid Crystal Filaments – Tanya Ostapenko Mon. May 18th, 2015
12:30 pm-1:30 pm

Quasi-one-dimensional free-standing fluid structures are not often found in nature, but may be formed by any material that can overcome capillary instability. Once this instability is suppressed, long filaments, with a length-to-diameter ratio greater than �, may form. Liquid crystals are an extraordinary system that can form free-standing fluid filaments with length-to-diameter ratios exceeding 7000. Buckling instabilities in freestanding liquid crystal filaments formed from bent-core liquid crystals in the B7 phase may be induced in a variety of ways, e.g. by acoustical or electrical vibration. However, this talk will focus on instabilities induced by compressing the filament, as well as those from a mechanical or thermal rupture.

Quantum Phase Transitions in Magnets – Ribhu Kaul Mon. May 11th, 2015
12:30 pm-1:30 pm
Cosmology with Planck’s Observations of the Cosmic Microwave Background – Brendan Crill Thu. May 7th, 2015
2:15 pm-3:15 pm

The Planck satellite was launched in 2009 and mapped the full sky in nine bands from 30 to 857 GHz, and has produced the most accurate to-date full sky maps of the temperature and polarization of the cosmic microwave background. The measurements are consistent to high precision with a spatially flat universe dominated by cold dark matter and a cosmological constant. The Planck data are consistent with single-field inflationary models. Planck’s unprecedented characterization of polarized Galactic foreground emission has important implications for current and future sub-orbital measurements of the CMB, particularly as revealed by a joint analysis of Planck and BICEP2/Keck array data.

Gravitational Signals from Noise in the Hubble Diagram – Edward Macaulay Tue. May 5th, 2015
11:30 am-12:30 pm

Understanding the nature of the dark universe requires precise measurements of the background expansion history, and also the growth rate of density fluctuations. In this talk, I’ll consider both regimes with supernova lensing for the OzDES spectroscopic survey – which is measuring the redshifts of hundreds of supernova and thousands of galaxies identified by the Dark Energy Survey. I’ll start by reviewing the more established method of growth rate measurements with Redshift Space Distortions, and discuss possible tension between RSDs and expectations from Planck CMB measurements. I’ll then consider how OzDES can place novel constraints on the growth rate and amplitude of density fluctuations by correlating noise in the supernova Hubble diagram with the gravitational effects of lensing and peculiar velocities expected from the observed density field.

One century of neutrino mass experiments: from radium salts to microwaves – Benjamin Monreal Mon. April 27th, 2015
4:15 pm-5:15 pm

The neutrino mass is one of the longest-standing unanswered questions in particle physics. We’ve recently learned a tremendous amount about how the weak interaction mixes neutrino mass states together; we’ve learned that there are three different masses, and we’ve narrowed the ordering of these masses down to two possibilities; but we still haven’t learned what the masses actually are. The KATRIN experiment, soon to start data taking, will use a huge electrostatic spectrometer to search for the signature of a massive neutrino in beta decay, but astrophysicists predict that the mass scale is too small for KATRIN to see. Project 8’s microwave spectrometry technique may provide the next,

A career in clean energy – Philip Farese Thu. April 23rd, 2015
11:30 am-12:30 pm
Thank You for Flying the ‘Vomit Comet’: Using Parabolic Flights to Examine Quantitatively the Stability of Liquid Bridges Under Varying Total Body Force – Greg DiLisi Mon. April 20th, 2015
12:30 pm-1:30 pm

Liquid bridges were flown aboard a Boeing 727-200 aircraft in a series of parabolic arcs that produced multiple periods of microgravity. During the microgravity portion of each arc, g_eff , the effective total body acceleration due to external forces became negligibly small so that cylindrical liquid bridges could be suspended across two coaxial support posts. Near the bottom of each arc, g_eff slowly increased to a maximum of 1.84g, causing the liquid bridges to deform and in some cases collapse. Although the physics of liquid bridges subject to varying total body force is well-established and has been analyzed extensively both theoretically and experimentally,

Novel measurement methods for probing magnetic nanoparticles – Yumi Ijiri Thu. April 16th, 2015
4:15 pm-5:15 pm

Magnetic nanoparticles are the focus of much current research with uses ranging from data storage in hard drives to targeted drug delivery in biomedical devices to smart fluids in automotive braking. These applications all depend critically on the intrinsic properties of the nanoparticles and the manner in which they interact; unfortunately, many traditional methods to investigate magnetic materials either average out the variations or provide information on only isolated particles in environments much different than in applications. To address these issues, my students and I have been working with a variety of collaborators on two different types of experiments with magnetic nanoparticles: one involving a technique known as polarized small angle neutron scattering to study the magnetic ordering of the particles and the second involving a variation of a fluid flow magnetic field fractionation approach to study the clustering.

Stochasticity in ecological dynamics – Karen Abbott Thu. April 9th, 2015
4:15 pm-5:15 pm

Population dynamics result from a combination of deterministic mechanisms (e.g. competition, predation) that drive nonlinear dynamics and stochastic forces that disrupt the neat patterns that would otherwise result. We often think of deterministic factors as being the most important, with their effects blurred secondarily by stochastic noise. In some particularly fascinating situations, however, it is unhelpful to thus emphasize deterministic drivers because stochasticity itself plays a role in shaping the overall pattern in the dynamics. In this way, stochasticity has a qualitative effect on the dynamics, such that dynamical patterns look quite different from what would result from the underlying deterministic factors alone.

The Race for the Highest Energy Neutrinos in the Universe – Patrick Allison Tue. April 7th, 2015
11:30 am-12:30 pm

In 1969, Berezinsky and Zatsepin predicted a flux of ultra-high energy (greater than 1 EeV) neutrinos due to cosmic ray interactions with the cosmic microwave background. These ‘cosmogenic’ BZ neutrinos are virtually “guaranteed” – barring extreme changes in either fundamental physics or our understanding of the source of cosmic rays, these neutrinos must exist. Detecting these neutrinos is extremely challenging, due to their incredibly low flux – however, recent experiments are approaching the sensitivity needed to finally make a detection. Here, I will talk about several of these existing and upcoming experiments, including the ANITA and EVA balloon-borne detectors, and the ARA experiment,

Music, Sweet and Sour – David Farrell Thu. April 2nd, 2015
4:15 pm-5:15 pm

Although the perceptual phenomena of consonance and dissonance in music have attracted interest across a wide variety of disciplines for two and a half millennia, theoretical progress to date has been very limited. With guidance from musicians at CIM, CWRU, and elsewhere, and in collaboration with Brooke Macnamara in CWRU’s department of psychological sciences, I have launched a new theoretical effort in the area. In my talk, I will review the fascinating history of the problem, discuss our first results, and outline plans for the future.

Macro Dark Matter – David Jacobs Tue. March 31st, 2015
11:30 am-12:30 pm

Dark matter is a vital component of the current best model of our universe, Lambda-CDM. There are leading candidates for what the dark matter could be (e.g. weakly-interacting massive particles, or axions), but no compelling observational or experimental evidence exists to support these particular candidates, nor any beyond-the-Standard-Model physics that might produce such candidates. This suggests that other dark matter candidates, including ones that might arise in the Standard Model, should receive increased attention. I will discuss the general class of dark matter candidates with characteristic masses and interaction cross-sections characterized in units of grams and square centimeters, respectively —

V2O5, a Strongly Correlated 2D System with 1D Aspects – Walter Lambrecht Mon. March 30th, 2015
12:30 pm-1:30 pm

V2O5 is a layered material with chains within the layer. I will discuss how this is manifested in its electronic band structure. The quasiparticle self-consistent GW method in this material strongly overestimates the band gap. The main reasons for this are examined and found to be a lattice polarization contribution to the screening of the electron-electron interaction. This is related to the large LO/TO phonon splittings in this material. Changes in band structure and phonons between bulk and monolayer will be discussed.

Multiscale Self-organization of Emulsion Droplets – Jasna Brujic Thu. March 26th, 2015
4:15 pm-5:15 pm

Self-assembly of inanimate objects into well-defined 3D structures, such as folded proteins or DNA-origami, remains a mystery. Inspired by biological systems, we design and make droplets stabilized by lipid mixtures and functionalized with cell-cell adhesion proteins or DNA. We discover that lipids phase separate on the droplet surface to create stable and tunable patterns of circular or stripy domains, reminiscent of lipid rafts in cell membranes. These domains carry adhesive proteins or DNA, which drive the specific and reversible binding between droplets to generate large scale structures. For example, we show that these mobile adhesion patches self-assemble linear chains of droplets into compact structures,

Wave Turbulence in Preheating – Henrique de Oliveira Tue. March 24th, 2015
11:30 am-12:30 pm

We have studied the nonlinear preheating dynamics of several inflationary models. They include nonminimally coupled scalar fields and two-fields models. It is well established that after a linear stage of preheating characterized by the parametric resonance, the nonlinear dynamics becomes relevant driving the system towards turbulence. Wave turbulence is the appropriated description of this phase since the matter contents are fields instead of usual fluids. Turbulence develops due to the nonlinear interations of waves, here represented by the small inhomogeneities of the scalar fields. We present relevant aspects of wave turbulence and presented the effective equation of state at the thermalize phase.

Predictive First-principles Simulations of Excited Electrons and Ultrafast Electron-ion Dynamics in Complex Materials – Andre Schleife Mon. March 23rd, 2015
12:30 pm-1:30 pm

Rapidly advancing high-performance super computers such as “Blue Waters” allow calculating properties of increasingly complex materials with unprecedented accuracy. In order to fully take advantage of leadership-class machines and to accurately describe modern materials, codes need to scale well on hundreds of thousands of processors. This talk focuses on electronic excitations and their ultrafast attosecond dynamics that are notoriously difficult to capture due to the quantum-mechanical electron-electron interaction. Being omnipresent in electronic and optical materials, an accurate description is a crucial factor for computational design of materials for technological applications.

It will be outlined how cutting-edge first-principles techniques based on many-body perturbation theory accomplish predictive theoretical spectroscopy of electronic excitations e.g.

Interacting particle models and phase transitions for social particles – Alethea Barbaro Thu. March 19th, 2015
4:15 pm-5:15 pm
Graphene on Ir(111), Adsorption and Intercalation of Cs and Eu Atoms – Pedrag Lazic Mon. March 16th, 2015
12:30 pm-1:30 pm

Experimental and theoretical study of Cs and Eu atoms adsorption on graphene on Ir(111) will be presented [1,2]. Graphene on Ir(111) surface is an interesting system because graphene has almost pristine electronic structure in it due to its weak bonding character to iridum surface. The bonding is almost exclusively of the van der Waals type. However adding Cs or Eu atoms graphene gets doped and and nature of binding changes – especially in the case when the atoms intercalate. Density Functional Theory calculations with standard semilocal functionals (GGA) – fail to reproduce experimental findings even qualitatively. Only when the newly developed nonlocal correlation functional is used (vdW-DF) which includes van der Waals interactions,

Opportunities and Challenges for Extreme Optics – Nader Engheta Thu. February 26th, 2015
4:15 pm-5:15 pm

Recent developments in condensed matter physics and nanoscience have made it possible to tailor materials with unusual parameters and characteristics. In my group, we have been exploring light-matter interaction in metamaterials and metastructures with extreme parameters, such as near-zero permittivity and near-zero permeability, and with extreme features such as very high phase velocity, very low energy velocity, extremely thin (one-atom-thick metasurfaces), subwavelength nonreciprocal vortices, extreme anisotropy, giant nonlinearity in phase-change dynamics, “static optics”, nanoscale computation in optical nanocircuits, and more. Such “extreme optics” will provide us with unprecedented features and functionalities in both wave physics and quantum optics and engineering.

March Meeting Preview Talks – Graduate Students Mon. February 23rd, 2015
12:30 pm-1:45 pm

APS March Meeting 2015 graduate student talks

Jiayuan Miao: Molecular-dynamics study of the Case-II diffusion of methanol in PMMA

Sukrit Sucharitakul: Field effect vs. Hall mobility in back-gated multilayered InSe FETs

Nicholas J. Goble: Effects of structural phase transitions on the interface of perovskite oxides

Bin Liu: Ultrastrong exciton-photon coupling in single and coupled organic microcavities

Ittipon Fongkaew: Electric field and spin-orbit coupling effects on the band structure of monolayer WSe2

Mapping New Physics with the Cosmic Microwave Background – Jeff McMahon Mon. February 23rd, 2015
11:30 am-12:30 pm

The Cosmic Microwave Background (CMB) is the afterglow of the big bang and the oldest light in the universe that can be observed. Faint signals in the pattern of the CMB provide information about the physics that govern the very early universe and the growth of large scale structure. Thus, precision measurements of the CMB provide unique views on ultra high energy physics (inflation); pressing mysteries including dark energy and dark matter; and traditional particle physics questions such as the sum of the neutrino masses. In this talk I present the state of the CMB field and highlight the Atacama Cosmology Telescope Polarimeter (ACTPol) and it successor Advanced ACTPol (AdvACT).

Optical Frequency Combs and Precision Spectroscopy – Jason Stalnaker Tue. February 17th, 2015
11:30 am-12:30 pm

Atomic spectroscopy has a long history of providing tests of fundamental physics. This tradition continues as the precision and accuracy of spectroscopic techniques improve. I will discuss the impact that the development of stabilized optical frequency combs has had on precision spectroscopy and describe an ongoing effort to study the atomic spectra of lithium at Oberlin College.

Exploring Soft Matter with DNA – Tomasso Bellini Mon. February 16th, 2015
12:30 pm-1:30 pm

The combination of solubility, coded pairing and adjustable flexibility make DNA a unique polymer for designing highly-controlled self-assembled complex nanostructures and novel materials. The same tools can be exploited to produce DNA-based systems enabling the exploration of challenging topics in soft matter physics. In the talk I will exemplify this approach by describing experiments and results in which DNA assembly was used to study living polymerization, liquid crystal ordering, the templating of chemical reactions, and phase behavior and gelation transition of low-valence colloidal particles.

Numerical Relativity in Spherical Polar Coordinates – Thomas W. Baumgarte Thu. February 12th, 2015
11:30 am-12:30 pm

Numerical relativity simulations have made dramatic advances in recent years. Most of these simulations adopt Cartesian coordinates, which have some very useful properties for many types of applications. Spherical polar coordinates, on the other hand, have significant advantages for others. Until recently, the new coordinate singularities in spherical polar coordinates have hampered the development of numerical relativity codes adopting such coordinates, at least in the absence of symmetry assumptions. With a combination of different techniques – a reference-metric formulation of the relevant equations, a proper rescaling of all tensorial quantities, and a partially-implicit Runge-Kutta method – we have been able to solve these problems.

Chemistry in Art, Art in Chemistry, and the Spiritual Ground They Share – Roald Hoffmann Thu. February 12th, 2015
4:30 pm-5:30 pm

After looking at the evolution of pigments for the color blue, Roald Hoffman, Frank H. T. Rhodes Professor of Humane Letters Emeritus at Cornell University and recipient of the 1981 Nobel Prize in Chemistry, will discuss how scientific articles relating to chemistry also deal with representation of an underlying reality, and face questions that are essentially artistic. The presentation will address the spiritual ground shared by art and a science as it poses the question Is there an analogue in science to abstract art?

The Chirality of SiO4 in Materials – David Avnir Wed. February 11th, 2015
12:30 pm-1:30 pm

SiO4 is a common building block of many materials, both crystalline such as quartz, silicates and zeolites, and amorphous, such as silica. Although intuitively one would think that SiO4 is an achiral perfect tetrahedron, in the vast majority of silicon-oxide based materials, that tetrahedron is of lower symmetry, to the degree of being chiral. Discussion of the chirality of SiO4 and its manifestation in crystalline and amorphous materials, will be the main focus of this lecture. Specific topics to be covered include the induction of chirality in silicas; the contribution of randomness to the emergence of chirality; the chirality of zeolites and silicates;

Teaching old materials new tricks: Making organic semiconductors crystallize on demand and metals emit light – Barry Rand Thu. February 5th, 2015
4:15 pm-5:15 pm

In this seminar, we will focus on two aspects of our work that look at materials which have been studied for quite some time, but try to utilize them in new and interesting ways. In the first part, we will focus on our recent efforts to template the growth of organic semiconductors. Through proper control of crystal phase, molecular orientation, and grain size (from nanometers to micrometers), we are able to realize higher solar cell performance from “classical” materials than otherwise possible. In the second part, we will look at metals, specifically Au and Ag. It turns out that metals,

Is Clustering Dark Energy Non-linear? The AP Resummation Approach – Stefano Anselmi Tue. February 3rd, 2015
11:30 am-12:30 pm

In order to gain insights on the mysterious component driving the acceleration of the Universe the future surveys will measure with unprecedent precision the density power spectrum in the non-linear range of scales and redshifts. On the theoretical hand those non-linearities require a comparable computational level. This is a tremendous effort that see deployed numerical (N-body), semi-analytical and analytical investigations. I this context I will present a powerful analytical resummation scheme first developed for LCDM and very recently extended to the Clustering Quintessence scenario, i.e. quintessence models with vanishing speed of sound. The approach I will expose allows predictions at few percent level beyond the Baryon Acoustic Oscillations range of scales,

Spin-dependent Scattering in Graphene: Electronic Birefringence and Kondo Transitions – Sergio Ulloa Mon. February 2nd, 2015
12:30 pm-1:30 pm

Graphene, a monoatomic layer of carbon, is perhaps the simplest and most easily available material where electrons behave as massless Dirac particles. Apart from the many promising technological applications, the study of graphene (and other layered materials) has opened a number of interesting theoretical questions: the microscopic crystalline structure requires an additional degree of freedom (the pseudo spin) that gives rise to effects such as the Klein paradox or Veselago electron lenses. The spin-orbit interaction (SOI) in materials arises from intrinsic lack of inversion symmetry in the lattice structure or from external or interfacial fields that break spatial symmetries. Although SOI is weak in natural graphene,

The 2014 Science Nobel Prizes – What were they given for? – Daniel Wesson from Neuroscience will give the Medicine or Physiology talk, Walter Lambrecht will give the Physics talk, and Andrew Rollins from Biomedical Engineering will give the Chemistry talk. Thu. January 29th, 2015
4:15 pm-5:15 pm

Physics:
This year’s Nobel prize in Physics went to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for their groundbreaking work in the development of blue light-emitting diodes, or LEDs. Walter will tell us how blue and subsequently white LEDs have become a vital energy-saving technology development, what difficulties had to be overcome to realize them, and how serendipity played a role in the key steps to unlock the potential of the key material gallium nitride to achieve them.

Medicine or Physiology:
The Nobel Prize in Physiology or Medicine in 2014 was awarded in one half to John O’Keefe and the other half to May-Britt Moser and Edvard Moser for “their discoveries of cells that constitute a positioning system in the brain”.

Sterile Plus Active Neutrinos and Neutrino Oscillations – Leonard Kisslinger Mon. January 26th, 2015
12:30 pm-1:30 pm

The talk will be based on recent neutrino oscillation experiments that have determined that there is almost certainly a sterile neutrino, with an estimate of the mixing angle.

Physics of the Piano – Nicholas Giordano Thu. January 22nd, 2015
4:15 pm-5:15 pm

Why des a piano sound like a piano? A similar question can be asked of virtually all musical instruments. A particular note, such as middle C, can be produced by a piano, a violin, and a clarinet. Yet, it is easy for even a musically untrained listener to distinguish between these instruments. One would like to understand why the sound of the “same” note depends greatly on the instrument. In particular, we would like to understand what aspects of the piano are most critical in producing its musical tones. The questions we will address in the talk include:

• Who invented the piano and why?

New Accelerators for Neutrino Physics – Matt Toups Tue. January 20th, 2015
11:30 am-12:30 pm

DAEδALUS is a proposed phased neutrino experiment, whose ultimate aim is to search for evidence of CP violation in the neutrino sector. The experiment will consist of several accelerator-based modules that produce decay-at-rest neutrino beams located at three different distances from a single, large underground neutrino detector. Each of these modules will make use of a pair of low-cost, high power cyclotrons to accelerate an H2+ beam initially up to 60 MeV with a compact injector cyclotron and then ultimately up to 800 MeV with a separated sector super-conducting cyclotron. These new low-cost, high power cyclotrons are motivated by industry needs and also open up new possibilities for searches for physics beyond the standard model with neutrinos.

Cooperation, cheating, and collapse in biological populations – Jeff Gore Thu. January 15th, 2015
4:15 pm-5:15 pm

Natural populations can suffer catastrophic collapse in response to small changes in environmental conditions as a result of a bifurcation in the dynamics of the system. We have used laboratory microbial ecosystems to directly measure theoretically proposed early warning signals of impending population collapse based on critical slowing down. Our experimental yeast populations cooperatively break down sugar, meaning that below a critical size the population cannot sustain itself. The cooperative nature of this microbial growth makes the population susceptible to “cheater” cells, which do not contribute to the public good and reduce the resilience of the population.

The Break-up of Viscoelastic Jets and Filaments: The Beads-on-a-string Structure – Marie-Charlotte Renoult Mon. December 1st, 2014
12:30 pm-1:30 pm

Capillary pressure can destabilize a thin stream of water and break it up into a succession of small droplets. The addition of a minute quantity (some part per million) of a long, flexible and water-soluble polymer is enough to modify the growth and morphology of this instability and leads, close to breakup, to the development of Beads-on-a-string structures (BOAS) where droplets are connected by thin threads. The BOAS phenomenon is also observed after stretching a bridge of a viscoelastic liquid.

Experiments on jets and stretched bridges of viscoelastic polymeric solutions were conducted to gain more insight into the formation and time evolution of the BOAS in both configurations.

The Universe as a Cosmic String – Florian Niedermann Tue. November 25th, 2014
11:30 am-12:30 pm

We are investigating modifications of general relativity that are operative at the largest observable scales. In this context, we are investigating the model of brane induced gravity in 6D, a higher dimensional generalization of the DGP model. As opposed to different claims in the literature, we have proven the quantum stability of the theory in a weakly coupling regime on a Minkowski background. In particular, we have shown that the Hamiltonian of the linear theory is bounded from below. This result opened a new window of opportunity for consistent modified Friedmann cosmologies. In our recent work it is shown that a brane with FRW symmetries necessarily acts as a source of cylindrically symmetric gravitational waves,

Spotting Majorana Fermions amidst Hofstadter butterflies and disordered landscapes – Smita Vishveshwara Thu. November 20th, 2014
4:15 pm-5:15 pm

In the hunt for Majorana particles, originally proposed in the context of particle physics, recent investigations have led to exciting prospects in superconducting wires, including possible experimental detection. This colloquium will first discuss how Majorana fermions can be present in ‘topological’ superconductors. Then, the rich interplay between potential landscapes and superconductivity will be explored in this context. As one instance, it is known that lattices subject to quasiperiodic potentials can give rise to beautiful Hofstadter butterfly patterns in phase space; these patterns can form the backdrop from which regimes containing Majorana fermions emerge. As another instance, in the presence of disorder,

Imprints of the Standard Model in the Sky? – Daniel G. Figueroa Tue. November 18th, 2014
11:30 am-12:30 pm

The existence of the Standard Model (SM) Higgs implies that a gravitational wave (GW) background is generated by the decay products of the Higgs, soon after the end of inflation. Theoretically, all Yukawa and SU(2)L gauge couplings of the SM are imprinted as features in the GW spectrum. However, in practice, the signal from the most strongly coupled species dominate, rendering inaccesible the information on the other species. This background could be used for inferring properties of particle physics, including beyond the SM, at energies way above the reach of LHC. To measure this background, however, new high frequency GW detection technology is required.

New Ideas for Dark Energy and Also for Dust Discrimination in B-mode Maps – Marc Kamionkowski Fri. November 14th, 2014
12:30 pm-1:30 pm
Intergalactic Magnetic Fields – Tanmay Vachaspati Tue. November 11th, 2014
11:30 am-12:30 pm

I will describe theoretical motivation for the existence of parity violating (helical) intergalactic magnetic fields and recent and growing observational evidence for such fields.

Soft Materials Approaches to Carbon Nanotubes: from Gels to Composites – Mohammed F. Islam Mon. November 10th, 2014
12:30 pm-1:30 pm

Carbon nanotubes combine low density with exceptional mechanical, electrical and optical properties. Unfortunately, these nanoscale properties have not been retained in bulk structures. I will describe surface modification assisted self‐assembly of single wall carbon nanotube into macroscopic nanotube networks  ‐  hydrogels and aerogels. The nanotube networks are ultra‐ lightweight, electrically conducting and thermally insulating. The shapes and sizes of these nanotube networks are readily tunable and is a tremendous strength of our fabrication method. The interesting properties and structure of these nanotube networks make them suitable for diverse applications. For example, we have used these networks as scaffolds to enhance elastic modulus of polymers by 40,000%.

Neutrino Oscillations at Work – Jenny Thomas Thu. November 6th, 2014
4:15 pm-5:15 pm

The observation that the three types of neutrino flavor oscillate among themselves led to the realisation that neutrinos have a very small but non-zero mass. This is extremely important because the supremely successful Standard Model of particle physics had expected, and indeed needed, the neutrinos to have exactly zero mass. Since the discovery of neutrino oscillations over the last 15 years, the parameters of the oscillations have been sufficiently well measured to turn neutrino oscillations into a tool for learning more about the elusive neutrino. I will explain the concept of neutrino oscillations, and report on the recent results from around the world in context with the new challenges now facing researchers of inferring the remaining unknown neutrino properties.

Peaks and Troughs in Large Scale Structure – Ravi K. Sheth Tue. November 4th, 2014
11:30 am-12:30 pm

I will reiew recent and substantial progress in modeling the cosmic web. This progress, which results from merging two different and decades old literature streams, leads to a number of new and interesting insights about how the biased tracers we will observe in the next generation of large scale structure datasets can better constrain cosmological models.

Physics and Language – Harsh Mathur Thu. October 30th, 2014
4:30 pm-5:30 pm

What Can We Learn about Language by Reading Millions of Books? (A Baker-Nord Digital Humanities Event) The dramatic growth of linguistic corpora enables the quantitative study of language

The dramatic growth of linguistic corpora enables the quantitative study of language
on a scale that would have been unimaginable even five years ago.
In this talk I will describe what we might learn about language
and its evolution from such studies, using the regularization of verbs as a concrete example.

Soft Magnetic Materials for Energy Applications in Extreme Environments – Matthew A. Willard Mon. October 27th, 2014
12:30 pm-1:30 pm

A fundamental transformation of the transportation sector in the United States is underway. In parallel with advances in renewable energy resources for power generation, the rising use of electric and hybrid vehicles is reshaping the future of public transportation. Similar efforts are moving forward for more-electric ships, aircraft, and other military technologies. Due to their prevalence, magnetic materials play an important role in improving the efficiency and performance of devices in electric power generation, conditioning, and conversion. However, significant challenges exist for magnetic materials especially when used for transportation technologies, where enhanced reliability, power density, and overall energy capacity are increasingly important.

High Precision Cosmology with BAO Surveys: BOSS and Future 21cm BAO Surveys – Hee-Jong Seo Fri. October 24th, 2014
12:30 pm-1:30 pm

The large scale structure of matter and galaxies contains important information on the evolution of the Universe. Baryon acoustic oscillations (BAO), which is one of the most promising large scale features, can provide an excellent standard ruler that enables us to measure the cosmological distance scales, and therefore dark energy properties. I would like to first discuss the ongoing joint analysis of BOSS galaxy and lya BAO results and, second, future 21cm BAO surveys focused on the effect of foregrounds.

On Demand 2D Electron Gas at LaAlO3/SrTiO3 Interfaces – Cheng Cen Mon. October 20th, 2014
12:30 pm-1:30 pm

The development of complex oxides over the past fifteen years has raised the prospect for new classes of electronic devices. In particular, it has been discovered that a high-mobility two-dimensional electron gas (2DEG) can be formed at the interface between two high-k insulators: LaAlO3 and SrTiO3. More interestingly, in samples with 3-unit-cell LaAlO3 (LAO) film grown on SrTiO3 (STO) substrate, a biased conducting atomic force microscope probe can locally and reversibly control the interfacial metal-insulator transition. This method is capable of patterning arbitrary conducting structures at LAO/STO interfaces with a spatial resolution of only a few nanometers. Based on such technique,

Sensing the ripples of time – Amar Vutha Fri. October 17th, 2014
12:30 pm-1:30 pm

Almost a century since the dawn of general relativity, we have yet to obtain direct evidence of one of its key predictions: gravitational waves. In this lecture, I will point out how the precisely regular vibrations of atoms in optical atomic clocks can be used to detect the minuscule ripples in time due to gravitational waves. This approach requires portable atomic clocks with high sensitivity and reliable performance. I will describe one approach to realizing such clocks, and lay out the prospects for gravitational wave imaging and astronomy using arrays of satellite-borne clocks. These detectors would complement the efforts to detect gravitational waves using terrestrial (Michelson) interferometers,

Constraining supersymmetry using molecules – Amar Vutha Thu. October 16th, 2014
4:15 pm-5:15 pm

Supersymmetry, and other theories that go beyond the Standard Model of particle physics, often predict the existence of new particles and interactions that act as sources of time-reversal violation. These, in turn, induce asymmetries in the charge distribution of electrons. In this colloquium, I will describe the stringent constraints on such new physics that were recently imposed by precise measurements with the thorium monoxide molecule (ACME Collaboration: Science, Jan 17, 2014). I will explain how polar molecules amplify the miniscule asymmetries of an electron’s charge distribution, how these molecules provide a useful suite of tools for experimenters, and the details of how we made the measurement.

Constraining supersymmetry using molecules – Amar Vutha Thu. October 16th, 2014
4:15 pm-5:15 pm

Supersymmetry, and other theories that go beyond the Standard Model of particle physics, often predict the existence of new particles and interactions that act as sources of time-reversal violation. These, in turn, induce asymmetries in the charge distribution of electrons. In this colloquium, I will describe the stringent constraints on such new physics that were recently imposed by precise measurements with the thorium monoxide molecule (ACME Collaboration: Science, Jan 17, 2014). I will explain how polar molecules amplify the minuscule asymmetries of an electron’s charge distribution, how these molecules provide a useful suite of tools for experimenters, and the details of how we made the measurement.

The Shape of the Electron, and Why It Matters – Amar Vutha Tue. October 14th, 2014
11:30 am-12:30 pm

The universe, or at least the 5% of it that we understand, is described rather well by the Standard Model of particle physics. Yet even this non-dark sector of the universe conceals a great mystery: // where has all the anti-matter gone? // In this lecture, I will describe the problem and the best solution that we have for it. One of the crucial ingredients of that solution is the prediction of new sources of time-reversal violation. The most sensitive probe of such time-reversal violation is, oddly enough, to be found in small asymmetries in the shape of the electron’s charge distribution.

The shape of the electron, and why it matters – Amar Vutha Tue. October 14th, 2014
11:30 am-12:30 pm

The universe, or at least the 5% of it that we understand, is described rather well by the Standard Model of particle physics. Yet even this non-dark sector of the universe conceals a great mystery: // where has all the anti-matter gone? // In this lecture, I will describe the problem and the best solution that we have for it. One of the crucial ingredients of that solution is the prediction of new sources of time-reversal violation. The most sensitive probe of such time-reversal violation is, oddly enough, to be found in small asymmetries in the shape of the electron’s charge distribution.

“How Big is the Proton Anyway?” – Amar Vutha Mon. October 13th, 2014
12:30 pm-1:30 pm
The proton is a bound state of quarks and gluons, described by the low-energy limit of quantum chromodynamics. Recent measurements using muonic hydrogen have, however, called our understanding of proton physics into question. In this first lecture, I will describe the significant discrepancy that exists between the recent muonic hydrogen measurements and previous measurements on protons — this is the // proton radius puzzle //. In the absence of any feasible theoretical solutions, new experiments might provide the best clues. I shall describe some of the experiments that are attempting to shed light on this puzzle, including our ongoing efforts to measure the proton radius via the Lamb shift in hydrogen atoms.
How big is the proton anyway? – Amar Vutha Mon. October 13th, 2014
12:30 pm-1:30 pm

The proton is a bound state of quarks and gluons, described by the low-energy limit of quantum chromodynamics. Recent measurements using muonic hydrogen have, however, called our understanding of proton physics into question. In this first lecture, I will describe the significant discrepancy that exists between the recent muonic hydrogen measurements and previous measurements on protons — this is the // proton radius puzzle //. In the absence of any feasible theoretical solutions, new experiments might provide the best clues. I shall describe some of the experiments that are attempting to shed light on this puzzle, including our ongoing efforts to measure the proton radius via the Lamb shift in hydrogen atoms.

Precision Cosmology with Galaxy Surveys: Understanding Intrinsic Alignments and Redshift-space Distortions – Jonathan A. Blazek Fri. October 10th, 2014
12:30 pm-1:30 pm

Galaxy imaging and redshift surveys, designed to measure gravitational lensing and galaxy clustering, remain the most powerful probes of large-scale structure. Such surveys constitute a significant fraction of current and next-generation projects in the cosmology community (e.g. DES, HSC, LSST, eBOSS, DESI, EUCLID, WFIRST). The statistical power of these experiments requires significantly improved understanding of astrophysical and observational effects. In this talk, I will focus on two important astrophysical processes which contribute systematic uncertainty but also contain a potential wealth of information. First, correlations in the intrinsic shapes and orientations of galaxies, termed “intrinsic alignments” (IA), are an important systematic in weak lensing.

Halide perovskites: their unusual combination of properties and its impact on solar cell applications – Walter Lambrecht Thu. October 9th, 2014
4:15 pm-5:15 pm

Hybrid organic/inorganic halide perovskites such as methylammonium lead iodide, (MA)PbI3, have recently burst on the solar cell scene with record efficiencies after only a few years of development. In this colloquium I will discuss some of the unique properties of these and related inorganic materials, such as CsSnI3 and their relation to their success in solar cell applications. I will show how the key feature of their electronic band structure results in a number of unusual properties. They are excellent hole conductors, they have an anomalous dependence of the band gap on temperature,

Spin-charge Conversion in Interfacial Electron Liquids – Giovanni Vignale Mon. October 6th, 2014
12:30 pm-1:30 pm

Semiconductor quantum wells, inter-metallic interfaces, layered oxides, and monolayer materials are all promising platforms for the observation of spincharge conversion due to strong spin-orbit interaction in the quasi two dimensional electron liquid they host. In this talk I focus on two closely related effects that can occur in these materials, namely the conversion of charge current to spin current (spin Hall effect) and the generation of spin polarization from an electric current (Edelstein effect). Together with their inverses (in the sense of Onsager reciprocity relations), these effects constitute a useful set of tools for spintronic applications. The theoretical challenge is to provide a unified treatment of the different mechanisms at work,

The Standard Model and Beyond with Ultracold Neutrons – Leah Broussard Thu. September 25th, 2014
4:15 pm-5:15 pm

Ultracold Neutrons (UCN) provide an excellent laboratory for precision studies of the Standard Model of particle physics, and can be used as a unique tool to probe the properties of other materials. The Ultracold Neutron facility at the Los Alamos Neutron Science Center has developed one of the brightest sources of UCN in the world. This facility is home to major experimental efforts to use UCN to determine the neutron beta decay lifetime, the angular correlations of the neutron spin with the decay proton and electron, the shape of the electron energy spectrum, and a new search for the electric dipole moment of the neutron.

Quantum Mechanics Without Measurements – Robert Griffiths Thu. September 18th, 2014
4:15 pm-5:15 pm

In standard (textbook) quantum mechanics, “measurement” provides an essential link between the formalism and its physical interpretation, but physical measurements cannot be analyzed in fully quantum mechanical terms (the infamous “measurement problem”). The (consistent or decoherent) histories interpretation employs fundamental quantum principles that apply universally to all quantum processes, including measurements, but make no reference to “measurement” as a fundamental concept. This approach provides a resolution of all the standard quantum enigmas (double slit, wave function collapse, etc.) as well as resolving the quantum measurement problem. The talk will provide an overview of the histories approach and indicate some of the objections to it.

The black hole information paradox and its resolution in string theory – Samir Mathur Thu. September 11th, 2014
4:15 pm-5:15 pm

Some 40 years ago Hawking found a remarkable contradiction: if we accept the standard behavior of gravity in regions of low curvature, then the evolution of black holes will violate quantum mechanics. Resolving this paradox would require a basic change in our understanding of spacetime and/or quantum theory. In recent years the paradox has found an interesting resolution through string theory. While quantum gravity is normally expected to be important only at distances of order planck length, the situation changes when a large number N of particles are involved, as for instance in the situation where we make a large black hole.

Building Nuclear Bombs in Your Basement: the technology of nuclear proliferation – R. Scott Kemp Thu. September 4th, 2014
4:15 pm-5:15 pm

Technology has been long understood to play a central role in limiting the proliferation of nuclear weapons. Over the last thirty years, however, systematic improvements in information, design, modeling, and manufacturing tools have eased that challenge. Could developing countries, or even small engineering firms, soon make nuclear weapons on their own? There is evidence that this transition has already occurred. This talk examines routes to the bomb that require only technologies already within reach of nearly any country without foreign assistance or access to export-controlled equipment or materials. It reports on a study of twenty historical nuclear programs, technical analyses,

Healthy Theories Beyond Horndeski – Jerome Gleyzes Wed. September 3rd, 2014
11:30 am-12:30 pm

In search for a candidate that could explain the current acceleration of the Universe, a lot of attention has been given recently to Galileon theories, or in their generalized form, Horndeski theories. They are interesting as they represent the most general scalar tensor theories that do not lead to equations of motion containing more than two derivatives. This restriction is generally thought to be of great importance, as generically, higher order derivatives lead to ghost instabilities. I will present a new class of scalar tensor theories that are broader than Horndeski and, as such, do bring higher order derivatives. However,

Interacting Spin-2 Fields – Johannes Noller Tue. September 2nd, 2014
11:30 am-12:30 pm

In this talk I will discuss some recent progress in our understanding of the spin-2 sector, focussing on theories with two or more dynamical such fields. In particular I will highlight the existence of several dualities in such models (generalisations of `Galileon dualities’), their decoupling limit phenomenology as well as the form of their interactions with other matter fields.

Getting research news out: connecting with the press and DIY communication – Kate McAlpine Thu. August 28th, 2014
4:15 pm-5:15 pm

Although fewer daily papers keep reporters on the science beat, science reporting is still thriving online, from large news organizations to popular science magazines to news stories from scientific institutions. I’ll tell you about what I have observed as a reporter and de facto press officer about getting research stories into these outlets. However, the web also allows researchers and science communicators to speak directly to the public. My personal favorite method is the rap video, so you will hear about a few of those, but many researchers write blogs, discuss science on social media, or participate in online outreach events.

Recent Progress in Large-Scale Structure – Roman Scoccimarro Fri. May 9th, 2014
11:00 am-12:00 pm

I will discuss recent progress in the understanding of how to model galaxy clustering. While recent analyses have focussed on the baryon acoustic oscillations as a probe of cosmology, galaxy redshift surveys contain a lot more information than the acoustic scale. In extracting this additional information three main issues need to be well understood: nonlinear evolution of matter fluctuations, galaxy bias and redshift-space distortions. I will present recent progress in modeling these three effects that pave the way to constraining cosmology and galaxy formation with increased precision.

Atom Interferometry Fundamentals and its Applications in Space Science – Babak Saif Tue. May 6th, 2014
11:30 am-12:30 pm
Shape of the Universe – Daniel Müller Tue. April 29th, 2014
11:30 am-12:30 pm

The most recent observations indicate that the Universe is isotropic, with a small spatial curvature, which can be either positive, negative or zero. As is well known, Einstein’s theory of gravitation restricts the spatially isotropic sections of space time to be locally S^3, H^3 or E^3, respectively. Thus, the topology of the Universe is only partly determined. On the other hand there are a few effects which occur for non trivial topology. In this talk, we will give a brief discussion of some of these, in particular of the Casimir effect which should have been important in the primordial stages of the Universe.

Our MRI Startup Grows Up: QED and HealthCare in 2014 – Hiroyuki Fujita Thu. April 24th, 2014
4:15 pm-5:15 pm

Dr. Fujita’s talk will focus on his MRI company and give a “State of QED” address, and how its accomplishments plus smart business practices such as investing heavily in human and R & D have helped him build a company that is profitable and providing well-paying jobs in an advanced manufacturing environment. He will explain that innovation is the cornerstones of success, while reviewing the RF principles of MRI. QED was an early adapter to new technology, such as additive manufacturing, which QED refers to as “Direct Digital Manufacturing” or “DDM” which has helped the company remain an industry leader when presented with technological challenges and opportunities that had to be met in order to stay competitive.

Testing Gravity via Lunar Laser Ranging – Tom Murphy Tue. April 22nd, 2014
11:30 am-12:30 pm

Forty years ago, Apollo astronauts placed the first of several retroreflector arrays on the moon. Laser range measurements between the earth and the moon have provided some of our best tests to date of general relativity and gravitational phenomenology–including the equivalence principle, the time-rate-of-change of the gravitational constant, the inverse square law, and gravitomagnetism. A new effort called APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) is now collecting measurements at the unprecidented precision of one millimeter, which will produce order-of-magnitude improvements in a variety of gravitational tests, as well as reveal more detail about the interior structure of the moon.

Chasing Inflation – John Ruhl Thu. April 17th, 2014
4:15 pm-5:15 pm

The Cosmic Microwave Background (CMB) has provided one of our most robust and powerful tools for learning about the contents and history of the universe. Temperature anisotropies mapped over a wide range of angular scales have given strong support to the basic 6-parameter “Inflationary Lambda Cold Dark Matter” cosmological model, and allowed us to measure those parameters exquisitely. For the past decade, several teams have been building instruments to search for a potential new signal from Inflation in the polarization of the CMB, of which the Bicep2 collaboration recently reported a detection. In this talk I will describe that signal,

Super-Resolution Microscopies at the Frontiers of Cell Biology (co-sponsored by the Institute for the Science of Origins) – Bill Dougherty Thu. April 10th, 2014
4:00 pm-5:00 pm

The ultimate resolution of an image acquired by an optical system (a telescope or microscope) is governed by the laws of diffraction and can be expressed as a limit in an optical transfer function (OTF). Typically, the OTF characterizing a given optical system is dominated by the physical properties of the principal optical element, for example the microscope objective. However, the optical “system” can be construed more broadly since the advent of fast digital imaging processing.

Using new strategies the OTF can be “extended” to extract previously undetectable high spatial frequency information, and thereby “see” finer detail, by numerical processing of an appropriate series of diffraction-limited images.

WIMP physics with direct detection – Annika H. G. Peter Tue. April 8th, 2014
11:30 am-12:30 pm

One of the best-motivated classes of dark-matter candidate is the Weakly-Interacting Massive Particle (WIMP). In this talk, I will discuss WIMPs in the context of direct-detection experiments. First, I will discuss a new signal for WIMP dark matter: gravitational focusing in direct-detection experiments. This effect leads to an energy-dependent phase-shift in the peak direct-detection event rate throughout the year. I will discuss this in light of current putative annual-modulation claims. Second, I will discuss what we can learn about WIMPs in the “early-discovery” days once WIMPs are conclusively found in direct-detection experiments. I will show that what we can learn about WIMPs depends sensitively on the ensemble of experiments that are running at the time of discovery.

Results from the LUX dark matter search, and prospects for the future – Tom Shutt Thu. April 3rd, 2014
4:15 pm-5:15 pm
Probing Dark Energy Using Growth of Structure: The Role of Simulations – Hao-Yi Wu Tue. April 1st, 2014
11:30 am-12:30 pm

The growth of cosmic structure provides a unique approach for measuring the dynamic evolution of dark energy and distinguishing different models of gravity. In this talk, I will focus on two of the most important methods for measuring the growth of structure: galaxy cluster counts and the redshift-space distortions of galaxy clustering. I will discuss the systematic uncertainties involved in both methods, and how I use numerical simulations to help reducing these systematics and improve our theoretical predictions.

Arrested Development (of Emulsions) – Tim Atherton Thu. March 27th, 2014
4:15 pm-5:15 pm

Emulsions – dispersions of “guest” fluid droplets inside another “host” fluid – are very familiar in everyday life as food, consumer products and as raw materials such as crude oil. Despite their ubiquity, they exhibit fascinating and complicated physics. In this talk, I present some recent work on a class of materials, Pickering Emulsions, that also include colloidal particles. With applications ranging from food products to cosmetics via targeted drug delivery systems, the particles provide an efficient way to control an emulsion’s structure, properties and functions. For example, particles adsorbed on the interface of the droplets can be used to control the rate at which they coalesce,

Nanoscale thermal transport – Alexis Abramson Thu. March 20th, 2014
4:15 pm-5:15 pm

Carbon nanostructures such as nanotubes, nanofibers and graphene have gained great attention over the past two decades. Owing to their unique properties, these nanomaterials have been proposed for use in a wide range of applications. For example, carbon nanostructures typically exhibit high thermal conductivities, making them particularly attractive for thermal management of electronics. Accurate and efficient thermal characterization holds the key to understanding the thermal transport mechanisms in these materials to assure their continued development for novel applications. This presentation will describe the techniques used for the characterization of thermal transport in individual carbon nanostructures and nanocomposites such as the thermal flash technique,

Science with CMB Spectral Distortions: a New Window to Early-Universe Physics – Jens Chluba Tue. March 18th, 2014
11:30 am-12:30 pm

Since COBE/FIRAS we know that the CMB spectrum is extremely close to a perfect blackbody. There are, however, a number of processes in the early Universe that should create spectral distortions at a level that is within reach of present day technology. I will give an overview of recent theoretical and experimental developments, explaining why future measurements of the CMB spectrum will open up an unexplored window to early-universe and particle physics, with possible non-standard surprises but also guaranteed signals awaiting us.

Curvature and defects in liquid crystals and other soft materials: Differential geometry isn’t just for cosmology any more! – Jonathan Selinger Thu. February 27th, 2014
4:15 pm-5:15 pm

Liquid-crystal membranes have a coupling between curvature and orientational order: Defects in the orientational order can induce curvature, and conversely, curvature leads to an effective geometrical potential acting on defects. In this colloquium, we present basic introductions to liquid-crystal physics and to differential geometry, and discuss the fundamental origin of the coupling. In particular, we show that several different types of coupling are possible, depending on whether the membranes are fluid or cross-linked, and on whether the interactions are fundamentally two- or three-dimensional. These theoretical considerations can explain experiments on lipid vesicles and liquid-crystal elastomer films, and provide opportunities to design membranes that will relax into selected shapes.

The Marvelous Success of the Standard Model of Cosmology – Lloyd Knox Wed. February 26th, 2014
12:30 pm-1:30 pm

The standard model of cosmology has been remarkably successful in its predictions for current data given earlier data. One can react with sadness for the lack of evidence for new physics, chase marginal anomalies, or marvel at the success and soldier on toward better measurements knowing new physics may be just around the corner. In this talk I will reveal some of the inner workings of this success in order to communicate why I find it marvelous. For example, for the predictions to agree with cosmic microwave background (CMB) data we need, at very high statistical significance, a cosmic neutrino background,

The Hunt for the Missing Components of the Universe: Dark Matter, Dark Energy . . . . and Women in Physics. – Evalyn Gates Thu. February 20th, 2014
4:15 pm-5:15 pm

In spite of much discussion and a variety of efforts aimed at increasing the number of women in physics, the entry level into the field has hit a wall. For the past 15 years the percent of B.S. degrees in physics awarded to women has remained flat at about 20%. It is also worth noting that the representation of African American students in physics declined over this same period. Engineering and computer science fields show similar trends. What can we do to change this?

21cm Cosmology – Ue-Li Pen Tue. February 18th, 2014
11:30 am-12:30 pm

I present recent developments in a new window to map the large scale structure of the universe through intensity mapping using the collective unresolved emission of cosmic hydrogen 21cm emission. Initial maps have been made with various existing telescopes, and an ambitious survey, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is under construction. Future potential science targets include precision measurements of dark energy, neutrino masses, and possibly gravitational waves.

Cosmology and Systematics of Multi-wavelength Galaxy Cluster Observables – Tomasz Biesiadzinski Tue. February 11th, 2014
11:30 am-12:30 pm

The current concordance lCDM cosmological model describes a universe where cold dark matter seeds structure formation and a cosmological constant drives its accelerated expansion. Precise measurements of various astronomical observables allow us to test this model and any deviations, if found, may lead to an improved cosmological theory. Ongoing and planned large scale surveys of the skies have the power to study the lCDM model. However the data sets they generate will be dominated by complex systematic uncertainties. One probe of cosmological parameters, the evolution of clusters of galaxies, has the power to differentiate simple models of dark energy, like the cosmological constant,

Quantum-Limited Superconducting Detectors and Amplifiers for Cosmology – Philip Mauskopf Fri. February 7th, 2014
12:30 pm-1:30 pm
Mercury’s interior: New views from MESSENGER – Steven Hauck Thu. February 6th, 2014
4:15 pm-5:15 pm

More than 35 years after Mariner 10 made its third and final flyby of the planet Mercury MESSENGER (short for MErcury, Surface, Space ENvironment, GEochemistry, and Ranging) became the first spacecraft to orbit the planet in March of 2011. Among the primary goals of the MESSENGER mission are to map its surface, determine the composition of the planet and its exosphere, and to constrain the structure of its interior and the nature of the planetary magnetic field. We will discuss highlights of some of MESSENGER’s major discoveries with a focus on what we are learning about both the construction and the evolution of the interior of the innermost planet.

The 2013 Science Nobel Prizes – What were they given for? – Martin Snider, Michael Weiss, Glenn Starkman Thu. January 30th, 2014
4:15 pm-5:15 pm

Dr. Martin Snider (Biochemistry) on the prize for Medicine or Physiology

Dr. Michael Weiss (Biochemistry)on the prize for Chemistry

Dr. Glenn Starkman (Physics) on the prize for Physics

21-cm Intensity Mapping – Jeffrey Peterson Tue. January 28th, 2014
11:30 am-12:30 pm
Next Steps in Neutrino Physics – Geralyn Zeller Thu. January 23rd, 2014
4:15 pm-5:15 pm

Neutrinos are among the most abundant particles in the universe, yet there is a surprising amount of information we still do not know about them. The discovery of neutrino masses and mixing over a decade ago has raised a large number of challenging questions about neutrinos and their connections to the world we live in. After briefly reviewing what we have learned about neutrinos so far, we will examine these open questions, explain why they are interesting, and discuss plans for answering them in future experiments.

The Physics of Climate Change – Michael Mann Thu. January 16th, 2014
4:15 pm-5:15 pm

I will review the basic scientific fundamentals behind human-caused climate change, including a discussion of physics-based theoretical climate models. I will motivate the use of a very simple (“zero-dimensional energy balance”) model of Earth’s climate. I will demonstrate, through applications of the model, how it can be used to address a number of outstanding scientific issues related to human-caused global warming. I will also discuss some of the societal implications of this work.

In proximity to novel physics: Topological Insulators coupled to Superconductors – Nadya Mason Thu. December 5th, 2013
4:15 pm-5:15 pm

Topological insulators (TI’s) are materials that are insulators in their interiors, but have unique conducting states on their surfaces. They have attracted significant interest as fundamentally new electronic phases having potential applications from dissipationless interconnects to quantum computing. In particular, coupling the surface state of a TI to an s-wave superconductor is predicted to produce the long-sought Majorana quasiparticle excitations, which could play a role in solid-state implementations of a quantum computer. A requisite step in the search for Majorana fermions is to understand the nature and origin of the supercurrent generated between superconducting contacts and a TI. In this talk,

Supersymmetry, Non-thermal Dark Matter and Precision Cosmology Tue. December 3rd, 2013
11:30 am-12:30 pm

Within the Minimal Supersymmetric Standard Model (MSSM), LHC bounds suggest that scalar superpartner masses are far above the electroweak scale. Given a high superpartner mass, nonthermal dark matter is a viable alternative to WIMP dark matter generated via freezeout. In the presence of moduli fields nonthermal dark matter production is associated with a long matter dominated phase, modifying the spectral index and primordial tensor amplitude relative to those in a thermalized primordial universe. Nonthermal dark matter can have a higher self-interaction cross-section than its thermal counterpart, enhancing astrophysical bounds on its annihilation signals. I will review recent progress in this program,

Cosmic Bandits: Exploration vs. Exploitation in Cosmological Surveys – Ely Kovetz Tue. November 26th, 2013
11:30 am-12:30 pm

Various cosmological observations consist of prolonged integrations over small patches of sky. These include searches for B-modes in the CMB, the power spectrum of 21-cm fluctuations during the epoch of reionization and deep-field imaging by telescopes such as HST/JWST, among others. However, since these measurements are hindered by spatially-varying foreground noise, the observational sensitivity can be improved considerably by finding the region of sky cleanest of foregrounds. The best strategy thus involves a tradeoff between exploration (to find lower-foreground patches) and exploitation (through prolonged integration). But how to balance this tradeoff efficiently? This problem is akin to the multi-armed bandit (MAB) problem in probability theory,

Fukushima: Implications for the Understanding of Severe Accidents and the Future of Nuclear Energy – M.V. Ramana Thu. November 21st, 2013
4:15 pm-5:15 pm

Like the earlier nuclear accidents at Three Mile Island (1979) and Chernobyl (1986), the multiple accidents at the Fukushima Daiichi nuclear plant will have an impact on both our understanding of severe accidents and on the likely future deployment of nuclear power. This talk will examine what happened at Fukushima from the viewpoint of multiple perspectives on nuclear safety. This will be followed by an examination of how governments in different countries have responded to the accident, and how this could affect plans for constructing nuclear reactors around the world over the coming decades.

Turning trajectories in multi-field inflation – Krzysztof Turzyński Tue. November 19th, 2013
11:30 am-12:30 pm

The latest results from the PLANCK collaboration, consistent with the simplest single-field models of slow-roll inflation and with no trace of non-Gaussianity, have extinguished many hopes of seeing specific aspects of New Physics directly in the sky. One may then wonder whether the landscape of allowed inflationary models has been practically reduced to single-field effective theories. I shall argue that the answer is negative and present several inflationary models in which the turn-induced interactions between two scalar fields affect the normalization/running of the power spectrum of curvature perturbations, or smooth out its features (e.g. via particle production), actually driving the power spectrum towards phenomenologically acceptable characteristics.

Lorentz violation in gravity: why, how and where – Diego Blas Mon. November 18th, 2013
3:00 pm-4:00 pm

Recent approaches to quantum gravity question the role of Lorentz invariance as a fundamental symmetry of Nature. This has implications for most of the observables in gravitational physics, also at low-energies. In this talk I will describe recent bounds on deviations from Lorentz invariance in gravity coming from binary pulsar observations and cosmological data.

Magnetism Without Magnetic Atoms: The Physics of the Vacancy Center in Graphene – Sashi Satpathy Thu. November 14th, 2013
4:15 pm-5:15 pm

Graphene is a material of considerable current interest owing to its linear band structure and excitations that behave as massless Dirac fermions. In this talk, I will focus on the physics of a vacancy in graphene and show that it forms a magnetic center and, quite interestingly, it is also a Jahn-Teller center due to the coupling between the vacancy electronic states and the local lattice modes. However, the energetics are such that there is only a small potential barrier between the Jahn-Teller minima, leading to the quantum mechanical tunneling of the nuclei between the three minima, resulting in the dynamical Jahn-Teller effect.

Non-local quantum effects in cosmology – John Donoghue Tue. November 12th, 2013
11:30 am-12:30 pm

In general relativity, there are non-local quantum effects that come from the propagation of light particles including gravitons. I will review the effective field theory treatment which allows one to identify the reliable parts of the quantum loops. In cosmology, there are then non-local corrections to the FLRW equations. I will present some of the formalism for this and give some exploration of results.

New Possibilities in Transition-metal oxide Heterostructures – Wei-Cheng Lee Fri. November 8th, 2013
12:30 pm-1:30 pm

Heterojunction, the interface between two dissimilar crystalline materials, has been one of ideal platforms for the two-dimensional electronic systems (2DES). Examples include the quantum Hall effect which was first observed in the semiconductor heterostructures. Recently, a heterostructure made from two transition metal oxides LaTiO3 and SrTiO3 has opened a new door for us to engineer the physical properties of transition metal oxides. In particular, since many of the transition metal oxides are strongly correlated materials, new types of 2DES with strong correlation could emerge from these new oxide interfaces. In this talk, I will first introduce the experimental and theoretical developments in this new field.

To Superconduct or Not to Superconduct; That is the Question – Michelson Postdoctoral Prizewinner Wei-Cheng Lee Thu. November 7th, 2013
4:15 pm-5:15 pm

Superconductor, a material losing resistivity below a critical temperature Tc, remains one of the grand challenges in physics. This field began in 1911 with the discovery of superconductivity in mercury at 4.2 K. After the birth of a complete microscopic theory of superconductivity proposed by Bardeen, Cooper, and Schrieffer in 1957, known as BCS theory, it was believed that no materials could have Tc higher than 30 K. The discovery of new classes of superconductors, cuprates in 1986 (which shatter the 30 K barrier) and iron pnictides in 2008, launched an international wave of research to find new materials with higher Tc.

To Superconduct or Not to Superconduct; That is the Question? – Wei-Cheng Lee Thu. November 7th, 2013
4:15 pm-5:15 pm

Superconductor, a material losing resistivity below a critical temperature Tc, remains one of the grand challenges in physics. This field began in 1911 with the discovery of superconductivity in mercury at 4.2 K. After the birth of a complete microscopic theory of superconductivity proposed by Bardeen, Cooper, and Schrieffer in 1957, known as BCS theory, it was believed that no materials could have Tc higher than 30 K. The discovery of new classes of superconductors, cuprates in 1986 (which shatter the 30 K barrier) and iron pnictides in 2008, launched an international wave of research to find new materials with higher Tc.

Novel Collective modes in Unconventional Superconductors – Wei-Cheng Lee Tue. November 5th, 2013
12:30 pm-1:30 pm

Unconventional superconductors are materials whose pairing mechanism is not due to the electron-phonon interaction as proposed by BCS theory. Up to date, known unconventional superconductors all exhibit symmetry-broken phases other than superconductivity in their phase diagrams, and it is widely-believed that the fluctuations associated with these symmetry-broken phases hold the key to the pairing mechanism of unconventional superconductors. In this talk, I will summarize our work in studying the collective excitations in cuprates and iron pnictides observed in inelastic neutron scattering and optical measurements. Their implications on the pairing mechanism will be discussed.

Orbital Aspect of Iron-based Superconductivity – Wei-Cheng Lee Mon. November 4th, 2013
12:30 pm-1:30 pm

In this talk, I will focus on the new classes of high-temperature superconductors, iron pnictides. While the magnetic interactions are certainly important in these materials, there have been significant evidences suggesting that the orbital degrees of freedom could play an important role as well. From both theoretical and experimental aspects, I will argue that the orbital degrees of freedom do play a game-changing role in physical properties of iron based superconductors. I will show that at the single particle level, the orbital order in the quasi-1D dxz and dyz bands induces a distortion of the Fermi surface, which could result in the structural phase transition.

Graphene at the Boundaries – Paul McEuen Thu. October 31st, 2013
4:15 pm-5:15 pm

With its remarkable structural, thermal, mechanical, optical, and electronic properties, graphene is a true interdisciplinary material. In this talk we will discuss experiments where graphene shows its many sides. For example, we will discuss atomic-scale imaging experiments of bilayer graphene that reveal the presence of 1D strain solitons between the layers. These strain solitons have recently been predicted to give rise to topologically protected 1D electronic edge states. We will also present measurements of the bending stiffness of graphene on micron scales. We find that graphene is thousands of times stiffer than predicted by atomic theories, but in good agreement with calculations that take into account the effects of thermal fluctuations on the bending stiffness.

Cosmology from conformal symmetry – Austin Joyce Tue. October 29th, 2013
11:30 am-12:30 pm

We will explore the role that conformal symmetries may play in cosmology. First, we will discuss the symmetries underlying the statistics of the primordial perturbations which seeded the temperature anisotropies of the Cosmic Microwave Background. I will show how symmetry considerations lead us to three broad classes of theories to explain these perturbations: single-field inflation, multi-field inflation, and the conformal mechanism. We will discuss the symmetries in each case and derive their model-independent consequences. Finally, we will examine the possibility of violating the null energy condition with a well-behaved quantum field theory.

The Cosmic Gravitational Wave Background – Tom Giblin Thu. October 24th, 2013
4:15 pm-5:15 pm

As we prepare for news from the Laser-Interferometer Gravitational Wave Observatory (LIGO) theoretical and computational physics are crawling over each other to identify cosmological sources of gravitational radiation in the LIGO sensitivity region. As one of those theorists, I will outline some of the progress we have made toward making precision predictions for gravitational radiation from cosmological sources. To the same end, I will discuss the limitations of observing cosmological sources at LIGO and why precision estimates are so important at this time. I will also present a “rule of thumb” that can be used to quickly evaluate to-good-to-be-true predictions.

Dark Materials: the Topology of Insulators – Harsh Mathur Thu. October 17th, 2013
4:15 pm-5:15 pm

Topological insulators are insulating materials with conducting surfaces. In this talk I will introduce topology by its application to the analysis of tie knots. I will then describe the remarkable electrostatics of topological insulators that mimics the behavior of axion domain walls studied in particle physics. Possible experiments to observe this physics will be discussed. Finally I will give a pedagogical introduction to the Su-Schrieffer model, a simple one dimensional analog of a topological insulator. My collaborators and I have proposed a photonic realization of this model that has now been observed experimentally.

Goldstone bosons with spontaneously broken Lorentz symmetry – Riccardo Penco Tue. October 15th, 2013
11:30 am-12:30 pm

In this talk, I will discuss some general properties of effective theories of Goldstone bosons in which Lorentz symmetry is spontaneously broken. I will first introduce an extension of Goldstone theorem to systems with a finite density of charge. This very general setting is potentially applicable to contexts as diverse as early universe cosmology and QCD at finite density. Additionally, I will show how certain effective theories of Goldstones with broken Lorentz symmetry admit UV completions that do not restore any broken symmetry.

Isostatic Lattice: From Jamming to Topological Surface Phonons – Tom Lubensky Thu. October 10th, 2013
4:15 pm-5:15 pm

Frames consisting of nodes connected pairwise by rigid rods or central-force springs, possibly with preferred relative angles controlled by bending forces, are useful models for systems as diverse as architectural structures, crystalline and amorphous solids, sphere packings and granular matter, networks of semi-flexible polymers, and protein structure. The rigidity of these networks depends on the average coordination number z of the nodes: If z is small enough, the frames have internal zero-frequency modes, and they are “floppy”; if z is large enough, they have no internal zero modes and they are rigid. The critical point separating these two regimes occurs at a rigidity threshold,

Slavnov-Taylor Identities for Primordial Perturbations – Lasha Berezhiani Tue. October 8th, 2013
11:30 am-12:30 pm

I will show that all consistency relations for the primordial perturbations derive from a single, master identity, which follows from the Slavnov-Taylor identity for spatial diffeomorphisms. This master identity is valid at any value of momenta and therefore goes beyond the soft limit. This approach underscores the role of spatial diffeomorphism invariance at the root of cosmological consistency relations. It also offers new insights on the necessary conditions for their validity: a physical contribution to the vertex functional must satisfy certain analyticity properties in the soft limit in order for the consistency relations to hold. For standard inflationary models, this is equivalent to requiring that mode functions have constant growing-mode solutions.

Modeling and simulating cellular processes in the brain: a mathematical challenge – Daniela Calvetti Thu. October 3rd, 2013
4:15 pm-5:15 pm

Abstract: Understanding human brain is one of the greatest challenges of science, not the least because, almost by definition, it is too complex to be understood by a human brain. The brain accounts for about 2% of our body weight, yet it consumes about 20% of the oxygen we intake, showing how central the energy metabolism must be for signalling. What we know about the functioning of the brain is based on indirect information: brain imaging, cell cultures and animal models. Therefore, to quantitatively integrate the information into a comprehensive picture requires an across-the-scales mathematical model that, at the microscopic end of the scale,

Symmetry Breaking and Galileons – Garrett Goon Wed. October 2nd, 2013
11:30 am-12:30 pm

Galileons, and related theories, have deep connections to spontaneous symmetry breaking. After reviewing the origins of Galileon theories, I motivate their interpretation as Goldstone Bosons and illustrate some of their special technical properties before proceeding to discuss applications and future directions.

Michelson and Morley –the men, the experiment, and the 1987 Centennial Celebration – Various + P. Taylor Thu. September 26th, 2013
4:15 pm-5:15 pm

The Michelson-Morley experiment is arguably the most important measurement ever performed in the history of science. If its result had been different, then our whole conception of space and time would be very far from the picture that Einstein gave us in his special theory of relativity.

The collaboration between these two great men was literally born in fire, and was ended by an arrest. After a brief discussion of the history and importance of the experiment, and a description of the remarkably dissimilar personalities of Cleveland’s two most famous scientists, we will see some excerpts from the 1987 Celebration at which all but one of America’s living Physics Nobelists spoke.

CMB Lensing: reconstruction from polarisation & implications for cosmology from cross correlation with galaxies – Ruth Pearson Tue. September 24th, 2013
11:30 am-12:30 pm

CMB Lensing is a probe of the matter distribution between the surface of last scattering and today, which has been measured using CMB temperature data. Signal to noise for lensing reconstruction from CMB polarisation data is expected to be much better, since B modes on small scales should vanish in the absence of lensing. An effect of having data from an incomplete sky is leakage of E mode power in to B mode power. Upcoming data analysis from ground based CMB polarisation instruments must account for this effect. In the first part of my talk I will show results for CMB polarisation lensing reconstruction from small patches of sky,

Green commercial buildings: are they saving energy or are they just making us feel good? – John Scofield Thu. September 19th, 2013
4:15 pm-5:15 pm

US buildings consume roughly 40% of the nation’s primary energy and are responsible for a similar fraction of our greenhouse gas emission. There is tremendous documented potential for lowering both of these figures through cost-effective energy efficiency improvements in buildings. Green building rating systems such as ENERGY STAR and LEED represent national efforts to realize these savings. But what do the data tell us about their success in reducing building energy consumption and greenhouse gas emission. Because building energy data are the property of building owners energy performance data are limited. What little data we have shows us that 1) there is a huge performance gap between a building’s predicted energy consumption and its measured consumption.

To wet or not to wet? That is the Question – Milton Cole Thu. September 12th, 2013
4:15 pm-5:15 pm

If one looks at a leaf of a plant after a rainfall, one sees water droplets of varying sizes. What determines this “wetting” behavior? The answer, known in principle for two centuries, involves the surface tension of the water itself, as well as the two surface tensions at the water-leaf interface (liquid-leaf and vapor-leaf). At the microscopic level, the wetting behavior depends on the relationship between two interactions: the cohesive interaction between two water molecules and the adhesive interaction between a water molecule and the leaf.

In this talk, I will report the first wetting phase transition for water ever to be seen.

Making the connection between galaxy voids, dark matter underdensities and theory – Paul Sutter Tue. September 10th, 2013
11:30 am-12:30 pm

TBA

Light or Dark? Mass and Gravity in the Universe – Stacy McGaugh Thu. September 5th, 2013
4:15 pm-5:15 pm

We now have a well developed cosmological paradigm, LCDM, in which most of the mass-energy is composed of unknown dark components. This picture provides a satisfactory description of large scale structure but has serious failings on the small scales of individual galaxies. Simultaneously, we have some unlikely successes of an alternative theory of gravity, MOND, in predicting the dynamical behavior of galaxies while offering little in the way of a cosmology. Neither theory obviously subsumes the other, posing a dilemma with profound implications.

“Look to the Stars” – an episode starring Case’s first Physics Professor – Albert A. Michelson Thu. August 29th, 2013
4:15 pm-5:15 pm

The semester’s first colloquium will be somewhat out of the ordinary – a screening of an old TV episode. The highly popular and long-running series Bonanza was a staple of American television from the late 1950s until the early 1970s, and continues in syndication. The series often tackled difficult and highly charged cultural themes. Here, a 1962 episode centers on high school-aged and Case-physics-professor-to-be Albert Michelson’s dealings with science, education, and bigotry in the Old West. The show’s science and history may be somewhat dubious, but it provides an interesting and amusing insight into late 19th century frontier culture and a connection with our own department.

Ordered self-assembly of molecules on gold substrates, for activated organic monolayers – Prof. Emmanuelle Lacaze Wed. July 17th, 2013
12:30 pm-1:30 pm

Photochromic molecules are characterized by a functional group whose configuration is modified by absorption of light, in a reversible manner. They could be at the basis of new electronic displays which would be activated by light irradiation. For the formation of ultra-thin electronic displays, researchers now try to adsorb them on metallic substrates. Two main questions are thus asked : Firstly, is it possible to self-assemble this type of molecule on a substrate. Second, when self-assembled in monolayer, do the molecules remain active under irradiation, and most importantly, can they be locally switched under STM tip Ordered self-assemblies have been successfully obtained with azo-benzene based photochromes,

Topological transition of graphene from quantum Hall metal to quantum Hall insulator – Prof. XiangRong Wang Fri. May 17th, 2013
12:30 pm-1:30 pm

In this talk, I will first review the basic electronic properties of graphene. In particular, I will explain why the recently observed insulating phase of graphene at charge neutrality point in high magnetic field quantum Hall (QH) experiments is a big surprising. Then I will present a simple single-particle theory for this intriguing finding. We show that the magnetic field driven Peierls-type lattice distortion (due to the Landau level degeneracy) and random bond fluctuations compete with each other, resulting in a transition from a QH-metal state at relative low field to a QH-insulator state at high enough field at the charge neutrality point.

The Universe in a New Light: the First Cosmological Results from the Planck Mission – Bill Jones Tue. April 30th, 2013
2:30 pm-3:30 pm

The precision and accuracy of the recently released Planck data are without precedent; the data from a single experiment provide all-sky images at wavelengths never before explored, covering more than three decades in angular scale with a signal dynamic range exceeding a factor of a million. These data open new avenues of research in fields ranging from Galactic astrophysics to cosmology. Our present Universe has shown herself to be both simple and elegant, and although her origins remain enshrouded in mystery, it appears that her past may have been more complex. While the Planck data have begun to inform us about the nature of cosmo-genesis,

Detecting Modified Gravity in the Stars – Jeremy Sakstein Mon. April 29th, 2013
10:30 am-11:30 am

Screened scalar-tensor gravity such as chameleon and symmetron theories allow order one deviations from General Relativity on large scales whilst satisfying all local solar-system constraints. A lot of recent work has therefore focused on searching for observational signatures of these models and constraining them. If these models are to be viable then our own solar system is necessarily screened, however, this may not be the case for stars in dwarf galaxies, which can exhibit novel and unique phenomena. These new effects can be exploited to produce constraints that are far more competitive than laboratory and cosmological tests and in this talk,

Quantum Fluids of Light – David Snoke Mon. April 29th, 2013
12:30 pm-1:30 pm

In the past few years a new class of solid state optical systems has been developed in which photons have an effective mass and a repulsive interaction between each other. These renormalized photons are known as “polaritons”. One way of looking at this type of system is as an optical medium with world-record nonlinearity, leading to new possibilities for modulating light. Another way of looking at this type of system is as an analogue of a gas of atoms, which can undergo Bose-Einstein condensation and can become superfluid, allowing us to study superfluidity in a new way. I will review the basic experimental methods and recent results of polariton superfluids.

Semiconductor nanowires : from LEDs to solar cells – Silvija Gradecak Mon. April 22nd, 2013
12:30 pm-1:30 pm

Semiconductor nanowires are quasi-one-dimensional single-crystals that have emerged as promising materials for the development of photonic and electronic devices with enhanced performance. Nanowires offer solutions to some of the current challenges in science and engineering, but realization of their full potential will be ultimately dictated by the ability to control their structure, composition, and size with high accuracy. In this talk, I will discuss our recent results on the controlled growth, doping, and applications of III-V nanowires, as well as advanced electron microscopy techniques for direct correlation of structural and physical properties with high spatial resolution. We have developed a simple,

Senior Project Symposium Sat. April 20th, 2013
11:30 am-12:30 pm
Some Experiences Gained in Starting and Growing Optical Companies – James C. Wyant Thu. April 18th, 2013
4:15 pm-5:15 pm

This talk will describe some experiences gained in starting and growing two optical companies, WYKO Corporation (1984-1997) and 4D Technology (2002-present). Both companies designed, manufactured, and sold computerized interferometric systems for the measurement of surface shape and surface roughness. Founding, growing, and cashing out of WYKO was an unbelievable experience that was more fun than I ever dreamed anything could be. It was so much fun I felt I had to do it again. Both the fun parts and the not so fun parts for both WYKO and 4D will be discussed. The biggest surprises experienced and what I think are the most important factors in growing a successful high-tech company will be described.

In search for hints of resonance in the CMB power spectrum – Daan Meerburg Tue. April 16th, 2013
11:30 am-12:30 pm

We investigate possible resonance effects in the primordial power spectrum using the latest CMB data. These effects are predicted by a wide variety of models and come in two flavors, one where the oscillations are log spaced and one where the oscillations are linearly spaced. We treat the oscillations as perturbations on top of the scale invariant power spectrum. This allows us to significantly improve the search for resonance because it allows us to precompute the transfer functions. We show that the largest error from this simplification comes from the variance in the measurement to the distance of last scattering.

Mapping spin-orbit effects in semiconductors – Vanessa Sih Mon. April 15th, 2013
12:30 pm-1:30 pm
Spin-orbit coupling is a consequence of relativity but can be observed and used at the device scale to electrically initialize and manipulate electron spin polarization. Understanding how to exploit spin-orbit effects in non-magnetic semiconductors may enable the development of new devices with enhanced functionality and performance, such as spin-based devices that combine logic and storage and fast optical switches for information processing. In this talk, I will describe time- and spatially-resolved measurements of electron spin transport that enable sensitive measurements of the spin-orbit field and its dependence on applied electric fields and mechanical strain. These spin splittings also provide a mechanism for the electrical generation of spin polarization.
Origin of rigidity in granular solids – Bulbul Chakraborty Thu. April 11th, 2013
4:15 pm-5:15 pm

Granular materials such as sand or rice grains behave in ways that are often counterintuitive. An example is “footprints on sand” which owe their origin to a phenomenon known as dilatancy. Our intuition often fails because dry granular materials are non-cohesive, and live at zero temperature. The distinction between gases, liquids and solids is ill understood. These materials can solidify via non-equilibrium pathways in which applied stresses or boundary constraints play a crucial role. A striking example of this is shear-jamming, where an amorphous granular solid is created through the application of shear. This is in sharp contrast to our usual experience of shearing leading to flow.

Black Hole Space-Times from S Matrices – Ira Rothstein Tue. April 9th, 2013
11:30 am-12:30 pm

In this talk I will show how to generate classical space-times directly from S matrices. The method makes no use of Einsteins’ equations nor, for that matter, any space-time action at all. This approach also allows us to make direct contact between the classical solutions of Yang-Mills theory and those of gravity through the squaring relation between the Yang-Mills and gravitational tree level scattering amplitudes. In this way one may construct classical space-times directly from Yang-Mills theory. – 

Short-range order in nematic liquid crystals formed by reduced symmetry molecules – Sam Sprunt Mon. April 8th, 2013
12:30 pm-1:30 pm

Small molecules constructed from familiar chemical components, but with an unconventional (reduced symmetry) molecular shape, hold promise for developing nematic liquid crystals with macroscopic biaxiality or even polarity. These properties, realized over practical temperature ranges using thermotropic compounds, could open new avenues in technologies including optical displays, mechanical sensors, and low-cost personal power generation. I will report on recent studies of short-range order – a guidance, if not a direct precursor, to rational development of biaxial/polar nematics – in three types of reduced symmetry thermotropic materials: bent-core (V-shaped) liquid crystal compounds and rod-like molecules containing either lateral branches (Y-shaped) or bridges (H-shaped).

The discovery of a new particle. Is it the Higgs? – Daniela Bortoletto Thu. April 4th, 2013
4:15 pm-5:15 pm

On July 4th 2012 physicists working at the Large Hadron Collider (LHC), the world’s highest-energy proton accelerator, at CERN in Geneva, Switzerland announced the discovery of a new particle that is about 135 times heavier than a proton. This particle seems to closely resemble the Higgs boson that was hypothesized over forty years ago to explain the masses of all elementary particles in the universe. In this talk, I will summarize the context for this discovery and present the latest studies to elucidate the properties of this Higgs-like particle. I will conclude by discussing prospects for future measurements of this particle that will be allowed by the energy and luminosity upgrade of the LHC.

Testing gravity with pulsars, black holes and the microwave background – Lam Hui Tue. April 2nd, 2013
11:30 am-12:30 pm

We will discuss 3 topics: 1. a way to detect gravitational waves using binaries; 2. a way to test general relativity using black holes; 3. a way to connect superhorizon fluctuations with the observed statistical asymmetry of the universe.

Hybrid Quantum Devices with Single Spins in Diamond – Gurudev Dutt Mon. April 1st, 2013
12:30 pm-1:30 pm

Single spins associated with defects in diamond have emerged as a promising and versatile experimental system. They can be used as qubits in optically connected quantum networks, as sensors for magnetic imaging with sub-micron resolution, as readout heads for detecting and engineering quantum states of nano-mechanical oscillators, and even as probes in biological systems. I will discuss some of the key experimental progress and future prospects along these paths.

Random laser, bio-inspired laser, and time-reversed laser – Hui Cao Thu. March 28th, 2013
4:15 pm-5:15 pm

In this talk, I will review our studies of photonic nanostructures of random morphology. First, I show how we can trap light in such structures to make random lasers. Next, learning from the non-iridescent color generation by isotropic nanostructures in bird feathers, we use short-range order to enhance light confinement and improve lasing efficiency in artificial nanostructures. Finally I will introduce our recent work on time-reversed laser – coherent perfect absorber.

Neutrinoless double beta decay results from EXO-200 – Carter Hall Tue. March 26th, 2013
11:30 am-12:30 pm

Neutrinoless double beta decay has never been definitively observed, although for the last ten years one group has claimed to see a 6-sigma positive effect in 76Ge. Recently the EXO-200 experiment produced the first independent check on this claim using 136Xe. This talk will report on the double beta decay results from EXO-200 and other experiments, along with prospects for future progress in this field.

Point defect studies in ZnO: oxygen vacancy and p-type doping – Walter Lambrecht Mon. March 25th, 2013
12:30 pm-1:30 pm

In the first part of the talk, I will tell you about the controversy about the position of the defect levels for the oxygen vacancy in ZnO and how we tried to resolve it. In the second part, I will discuss the case of nitrogen in ZnO. I will discuss why nitrogen on an oxygen site forms a deep rather than shallow acceptor level. However, it is known that there exists a shallow level related to nitrogen doping. The question is then what defect complex is responsible for this shallow level? I will try to convince you that a N2 molecule located on a Zn-site has all the expected behavior of a shallow acceptor.

Hamiltonian Theory of Fractional Chern Bands – R. Shankar Thu. March 7th, 2013
4:15 pm-5:15 pm

It has been known for some time that a system with a filled band will have an integer quantum Hall conductance equal to its Chern number, a toplogical index associated with the band. While this is true for a system in a magnetic field with filled Landau Levels, even a system in zero external field can exhibit the QHE if its band has a Chern number. I review this issue and discuss a more recent question of whether a partially filled Chern band can exhibit the Fractional QHE. I describe the work done with Ganpathy Murthy in which we show how composite fermions,

Semiconductor nanocrystals for room-temperature coherent electronics: A flexible platform for manipulating spin coherence – Jesse Berezovsky Mon. March 4th, 2013
12:30 pm-1:30 pm

One route towards future electronics is to exploit interactions between coherent electron spin states and photons in semiconductor structures. This will require an understanding of the coherent evolution of spin states, the eventual decoherence of these states, and how these states interact with light, all in a scalable room-temperature system. In this seminar, I will present our work on spins in semiconductor nanocrystal quantum dots (NCQDs). This system provides a platform to study room-temperature coherent spin states and their interactions with light. In an NCQD, a spin optically initialized into a superposition of eigenstates remains coherent for approximately one nanosecond at room temperature.

Molecular interactions: linking physics and biology – Yi-Kuo Yu Thu. February 28th, 2013
4:15 pm-5:15 pm

Molecular interactions determine, for example, how transcription factors recognize their DNA binding sites, how proteins interact with each other, and consequently how a biological system functions. Since both proteins and DNAs are significantly charged, electric interactions are among the most important when studying biomolecular interactions. Despite a long history of research of complex systems such as biomolecules in solvent, these problems remain difficult even at the level of classical electrostatics and call for new schemes with controllable accuracy. When one wishes to study short range effects that require quantum mechanics, quantitative understanding is hindered by the presence of many electrons.

CMB Non-Gaussianity from Recombination and Fingerprints of Dark Matter – Cora Dvorkin Tue. February 26th, 2013
11:30 am-12:30 pm

In this talk, I show that dark matter annihilation around the time of recombination can lead to growing ionization perturbations, that track the linear collapse of matter overdensities. This amplifies small scale cosmological perturbations to the free electron density by a significant amount compared to the usual acoustic oscillations. Electron density perturbations distort the CMB, inducing secondary non-gaussianity, offering a means of detection by Planck and other experiments. I will present a novel analytic calculation of CMB non-gaussianity from recombination, providing a clear identification of the relevant physical processes. I will show that, even though electron perturbations can be markedly boosted compared with the standard model prediction,

Shedding some light on liquid crystalline organic semiconductors – Brett Ellman Mon. February 25th, 2013
12:30 pm-1:30 pm

We live in a world whose technology is ruled by a small set of inorganic semiconductors, notably silicon. Research on organic semiconductors (OSCs), molecular materials based on organic compounds, seeks to supplement the reigning paradigm rather than to supplant it. In particular, OSCs may improve photovoltaics, LEDs, sensors, and flexible, cheap electronics. In this talk, I will describe recent work at Kent State on liquid crystalline (LC) semiconductors, a subclass of OSCs that offer distinct advantages and disadvantages relative to more common crystalline or polymeric organics. After a (very) short introduction to the physics of OSCs and LCs, I will discuss how the ability to align the molecules in LC OSCs over macroscopic distances can (profoundly) improve transport characteristics.

Many Worlds, the Born Rule, and Self-Locating Uncertainty – Sean Carroll Thu. February 21st, 2013
4:15 pm-5:15 pm

A longstanding issue in attempts to understand the Everett (Many-Worlds) approach to quantum mechanics is the origin of the Born Rule: why is the probability given by the square of the amplitude? Recently, Page has raised another puzzle: the Born Rule itself is insufficient in cases where the wave function includes multiple indistinguishable observers in the same branch. We argue that both problems share a common solution, arising from a proper treatment of self-locating uncertainty (physical situations containing multiple copies of identical observers). This analysis gives a simple, physics-oriented derivation of the Born Rule, as well as a justification for the treatment of identical classical observers.

Nanostructures in Motion: Probing Surface Science and Fracture Mechanics at Molecular Level – Zenghui Wang Mon. February 18th, 2013
12:30 pm-1:30 pm

Nanomaterials, since their debut, have greatly advanced human knowledge from many aspects. For example, carbon-based nanomaterials, such as carbon nanotube and graphene, have been the subjects of intensive study over the last two decades and greatly improved our understanding of phenomena happening at the nanoscale. On the other hand, microelectromechanical systems, MEMS, research has thrived over the last few decades in the engineering field and brought along many new applications. In this talk, I will illustrate that, by combining nanomaterials with MEMS technology, even more new opportunities and new sciences can be unveiled. I will mostly focus two systems: 1.

Electrostatic charging of flowing granular materials – Dan Lacks Thu. February 14th, 2013
4:15 pm-5:15 pm

Contact charging occurs when two materials are brought into contact and then are separated. As a result of the contact, charge is transferred such that one material becomes charged positively and the other becomes charged negatively. Everyone is familiar with this effect, even children who have ‘experimented’ by rubbing a balloon on their hair and seeing the balloon and hair become highly charged. But which material charges positively and which charges negatively? The answer to this simple question is not really known. In contrast to the tremendous progress in most fields of science, the understanding of contact charging is not much better now than it was 2500 years ago.

Self-Assembly and Packing of Polyhedra into Complex Structures – Michael Engel Mon. February 11th, 2013
12:30 pm-1:30 pm

Isolating the role of building block shape for self-assembly and packing provides insight into the ordering of molecules and the crystallization of colloids, nanoparticles, proteins, and viruses. We investigated a large group of polyhedra whose phase behavior arises solely from their anisotropic shape. At intermediate packing density, our results demonstrate a remarkably high propensity for thermodynamic self-assembly and structural diversity. We show that from simple measures of particle shape and local order in the fluid, the assembly of a given shape into a liquid crystal, plastic crystal, or crystal can be predicted. Towards higher density, packing considerations dominate. Good packings can often be distinct from what is observed to assemble from the disordered state.

The 2012 Science Nobel Prizes – What were they given for? – George Dubyak (Physiology and Biophysics), Paul Tesar (Genetics), Harsh Mathur (Physics) Thu. February 7th, 2013
4:15 pm-5:15 pm

Three 15-minute talks on the 2012 Nobel prizewinners and their work.

The 2012 Nobel Prize in Physics: Making Gedanken Experiments Real.

The 2012 Nobel Prize in Physics was awarded to Serge Haroche and David Wineland for experimental methods that allow the measurement and manipulation of individual quantum systems. I will briefly describe their complementary experimental methods, their ground breaking experiments, and possible implications for clocks, computers and cats.

The 2012 Nobel Prize in Chemistry Award to Robert Lefkowitz and Brian Kobilka: G Protein-Coupled Receptors as Key Mediators of Biological Communication and Regulation

A fundamental aspect of biological regulation is that cells can sense many types of changes in their external environment and respond to these extrinsic cues with appropriate functional adaptation in their internal biochemistry.

Routing Light with Spatial Solitons: Light Localization and Steering in Liquid Crystals – Antonio DeLuca Mon. February 4th, 2013
12:30 pm-1:30 pm

Nematic Liquid Crystals (NLCs) support strong nonlinear effects, most of them due to the high birefringence and non-local response. Light self-confinement via reorientational nonlinearity and nonlocality, yields to the creation of robust light filaments named ‘optical spatial solitons’, which can trap, switch and route optical signals. In the last ten years, the attention to NLC systems, due to their large and polarization dependent nonlinearity, allowed the observation of self-focusing and spatial solitons with a significant attention devoted to reduce thermal contributions to the nonlinear phenomena and lower the required optical power. In all the observed cases, self-confinement was observed over short distances (hundreds of micrometers) and with non-negligible thermo-optic effects.

Unifying theory for universal quake statistics: from compressed nanopillars to earthquakes – Karin Dahmen Thu. January 31st, 2013
4:15 pm-5:15 pm

The deformation of many solid and granular materials is not continuous, but discrete, with intermittent slips similar to earthquakes. Here, we suggest that the statistical distributions of the slips, such as the slip-size distributions and their cutoffs, all follow approximately the same regular (power-law) functions for systems spanning 13 decades in length, from tens of nanometers to hundreds of kilometers; for compressed nano-crystals, amorphous materials, sheared granular materials, lab-sized rocks, and earthquakes. The similarities are explained by a simple analytic model, which suggests that results are transferable across scales. This study provides a unified understanding of fundamental properties of shear-induced deformation in systems ranging from nanocrystals to earthquakes.

The Two-Envelope Paradox – Edwin Meyer Thu. January 24th, 2013
4:15 pm-5:15 pm

One of the most puzzling paradoxes in philosophy, mathematics and finance is the two-envelope paradox (http://en.wikipedia.org/wiki/Two_envelopes_problem). It is many years old, but it still generates 5-10 publications each year as many disciplines each have their own viewpoints and methods of attack.

Consider two sealed envelopes, one of which contains twice as much money as the other. You get to pick one and keep the amount inside. You pick one and reason thusly, “My envelope contains an amount which I’ll define as X. The other envelope must contain one-half X or twice X with a 50 percent chance of either.

Unparticles in Strongly Correlated Electron Matter – Philip Phillips Thu. January 17th, 2013
4:15 pm-5:15 pm

Several years ago, Howard Georgi introduced the concept of unparticles. Unparticle stuff has no particular mass. In fact, the mass of unparticle stuff looks the same on any number of scales in contrast to particle matter which has a definite mass. Another curious fact is that unparticles can carry current but make no contribution to the density of particles. In strongly correlated electron matter such as the high-temperature superconductors, the number of charge carriers that has a particle interpretation is less than the conserved charge. I will argue that unparticle stuff makes up the difference. The consequences of unparticle stuff for the physics of high-temperature superconductors will be explored.

Unveiling the Mystery of Mass – Christoph Paus Thu. December 6th, 2012
4:15 pm-5:15 pm

One of the prime reasons the Large Hadron Collider (LHC) was built is to resolve the question how particles acquire their mass. While it is very simple to measure particle masses, and we have a model (the Standard Model of Particle Physics) which explains quite accurately all presently available measurements, the seemingly trivial mechanism of how particle acquire their mass remains a mystery. The Standard Model invokes a new scalar gauge field to resolve this mystery, but we have until very recently not been able to find experimental evidence for its existence. On July 4, 2012, the CMS and ATLAS experiments announced the discovery of a new Higgs-like particle at a mass of about 125 GeV.

Odd tensor modes from particle production during inflation – Lorenzo Sorbo Tue. December 4th, 2012
11:30 am-12:30 pm

Several mechanisms can lead to production of particles during primordial inflation. I will review how such a phenomenon occurs and I will discuss how it can lead to the generation of tensor modes with unusual properties that might be detected in the not-so-far future. The gravitational waves produced this way can have a larger amplitude than in the standard scenarios, can violate parity, and their spectrum can display a feature that can be directly detected within the decade by second-generation gravitational interferometers such as advanced LIGO.

Terahertz plasmons and magnetoplasmons in graphene – Hugen Yan Mon. December 3rd, 2012
12:30 pm-1:30 pm

Plasmons in metal surfaces and clusters have been extensively studied due to their potential applications in sensing, imaging, light harvesting and optical metamaterials. Graphene is a semimetal with tunable conductivity and hence can support plasmons as well. In addition to the tunability, graphene plasmons have relatively weak damping due to the high carrier mobility. In this talk, I will present our recent progress on the plasmon excitations in graphene micro-structures and their behavior in an external high magnetic field. We demonstrated graphene plasmonic terahertz filters and polarizers with graphene/insulator stacks and revealed the unique properties of Dirac plasmons with and without a magnetic field.

Statics and Dynamics of Colloidal Particles in Liquid Crystals – Oleg Lavrentovich Thu. November 29th, 2012
4:15 pm-5:15 pm

Colloids and liquid crystals are two important classes of soft matter, usually explored independently of each other. The most studied colloids represent a dispersion of solid or liquid particles in an isotropic fluid such as water. The simplest liquid crystal, a nematic, is a fluid with long-range orientational order of molecules. This presentation reviews recent studies of liquid crystal colloids, i.e., dispersions of particles in a liquid crystal. The long-range orientational order imparts anisotropic elastic interactions of colloidal particles [1]. Elastic repulsion from the bounding walls opposes gravity and keeps the particles levitating in the liquid crystal bulk [2]. The levitating particles can be set into motion by applying an electric field.

Quantum Dots and Magnetic Quantum Dots for Biomedical Imaging and Separations – Jessica Winter Mon. November 26th, 2012
12:30 pm-1:30 pm

Quantum dots, semiconductor nanocrystals, have unique optical properties, including narrow emission bandwidths, broad excitation spectra, and remarkable photostability, which have made them excellent candidates for biological imaging. Since their introduction into the biological milieu in 1998, they have been applied for in vitro and in vivo imaging, diagnostic testing, and multiplexing. As researchers have appreciated the benefits of quantum dots for imaging, emphasis has shifted to fabricating nanocomposites containing quantum dots, and among these magnetic quantum dots have attracted significant attention. Here, we describe our efforts to fabricate quantum dots and magnetic quantum dots. Highlighting our most recent efforts in this area,

Advances in Solving the Two-Body Problem in General Relativity: Implications for the Search of Gravitational Waves – Alessandra Buonanno Tue. November 20th, 2012
11:30 am-12:30 pm

Compact binary systems composed of black holes and neutron stars are among the most promising sources for ground-based gravitational-wave detectors, such as the Laser Interferometer Gravitational Wave Observatory (LIGO) and its international partners. A detailed and accurate understanding of the shape of the gravitational waves is crucial not only for the initial detection of such sources, but also for maximizing the information that can be obtained from the gravitational-wave signals once they are observed. In this talk I will review progresses at the interface between analytical and numerical relativity. These advances have deepened our understanding of the two-body problem in general relativity,

Quench dynamics in one-dimensional systems – Aditi Mitra Mon. November 19th, 2012
12:30 pm-1:30 pm

How an interacting many-particle system which is initially out of equilibrium evolves in time, is a challenging question, especially for large system sizes where numerical simulations are difficult. The most puzzling issue is understanding the onset of thermalization, a process in which the system completely looses memory of its initial state, with the long time behavior characterized by only one or two parameters. Understanding this issue is important as ideal, thermally isolated systems, and their time-evolution can now be routinely studied in experiments. Using a novel time-dependent renormalization group approach I will show how a reduced part of a strongly interacting system can look effectively classical (or thermal) by being characterized by a dissipation and a noise,

Nuclear Q & A – William Fickinger Thu. November 15th, 2012
4:15 pm-5:15 pm

This talk addresses key questions associated with nuclear energy and weapons technologies and their impact on society. The intended audience includes journalists, politicians, scientists, political-scientists, activists, and students from high-schoolers through post-docs. The informal powerpoint presentation steps through key questions about nuclei, uranium, enrichment, reactors, weapons, and treaties. The goal is to better inform the public on critical issues which are often discussed but not very well understood. CWRU physics faculty and students should find these details useful in their role as responsible informed citizens.

Effective Field Theory for Fluids – Rachel Rosen Tue. November 13th, 2012
11:30 am-12:30 pm

In this talk I will present the low-energy effective field theory that describes the infrared dynamics of non-dissipative fluids. In particular, I will use the techniques of non-linear realizations developed by Callan, Coleman, Wess and Zumino, and Volkov to construct the effective theory based on the symmetry-breaking pattern of the fluid. I will discuss how this formalism can be used to incorporate quantum anomalies into the effective field theory.

Playing with monomolecular layers: model biological systems and liquid crystal alignment layers – Elizabeth Mann Mon. November 12th, 2012
12:30 pm-1:30 pm

Self-assembly within biological membranes controls structure, from the nano- to the microscale. The same physical processes also apply to synthetic systems. Here, I survey two different model systems for structure and dynamics within molecularly thin films.

Electro-active polymers and high-power-density energy storage – Jerry Bernholc Thu. November 8th, 2012
4:15 pm-5:15 pm

The usual means of storing electrical energy are either batteries, where the current induces chemical reactions, or capacitors, where especially chosen dielectrics enhance the stored energy. Since capacitors can be discharged far more quickly than batteries and fuel cells, they have much higher power densities. At present, highly insulating polymers with large breakdown fields, such as polypropylene, are the dielectrics of choice. Nevertheless, their energy densities are quite low because of small dielectric constants. Ferroelectric polymers from the polyvinylidene fluoride (PVDF) family have significantly larger dielectric constants, yet their energy densities are still rather low. However, an admixture of a small amount of another polymer results in a dramatic (up to sevenfold) increase in the stored energy.

Recent Results from CDMS II and The SuperCDMS Dark-matter Program – Raymond Bunker Tue. November 6th, 2012
11:30 am-12:30 pm

The Cryogenic Dark Matter Search experiment (CDMS II) was designed to directly detect dark matter by simultaneously measuring phonon and ionization signals caused by particle interactions in semiconductor targets, allowing event-by-event discrimination of signal from background via the relative sizes of the two signals. I’ll briefly review the CDMS II experiment and then focus on recent results related to the current low-mass WIMP controversy, including data from the CoGeNT, CRESST II, and DAMA/LIBRA experiments that hint at a low-mass WIMP signal and the (similarly sensitive) low-threshold and annual-modulation analyses performed by the CDMS II collaboration. I’ll also comment on the Collar and Fields likelihood analysis of the CDMS II low-energy data.

Half Metallic Ferromagnetism in Complex Oxides and Implications for Spintronics – Nandini Trivedi Mon. November 5th, 2012
12:30 pm-1:30 pm

I will discuss the mechanism behind the remarkable properties of double perovskites like Sr2FeMoO6 that show half-metallic ground states with 100% polarization and a ferromagnetic Tc above room temperature. I will conclude with a broad overview of other remarkable properties that can be achieved by changing the transition metal atoms. Reference: O. Erten, et. al Phys. Rev. Lett. 107, 257201 (2011).

Biosensing with Magnetic Nanoparticles – John Weaver Thu. November 1st, 2012
4:15 pm-5:15 pm

In Biology, many tools exist to study individual cells in culture but there is a paucity of tools to study the microenvironment in which cells live and grow in vivo. The microenvironment is the complex milieu of chemical and physical signaling that enables cells to form and function as organisms. Signaling between cells and extracellular structures is critical to normal growth and wound healing as well as malignant transitions and cancer growth. We have been exploring the use of magnetic nanoparticles to explore the microenvironment in vivo. It is not yet possible to image structures at microscopic scales in vivo as AFM does in vitro or as MRI does at macroscopic scales in vivo,

FUNCTIONAL FILMS AND CERAMICS – Alp Sehirlioglu Mon. October 29th, 2012
12:30 pm-1:30 pm

The presentation summarizes our recent efforts in developing new functional materials with a focus on operation in extreme environments. Discussion will include both fundamental aspects of behavior and the path to next generation of devices and applications. Two main topics will be discussed: (i) Oxide based heterointerfaces: Formation of a two dimensional conducting interface between two perovskite insulators (i.e., LaAlO3 on SrTiO3) was first reported in 2004. In 2006 it was reported for the first time that the conductivity of the hetero-interface could be switched between two states by application of an external field (analogous to gate voltage). This technologically significant but still infant discovery holds great potential for next-generation extreme environment electronics that can have both (i) higher information density and (ii) larger operation domain.

The First Quasars in Cosmic Structure Formation – Tiziana DiMatteo Thu. October 25th, 2012
4:15 pm-5:15 pm

As we are just attempting to understand how galaxy formation is connected to the growth of supermassive black holes, one fundamental challenge remains. Observations show us that the first quasars were assembled when the universe was only a tenth of its current age, yet their black holes are as massive as the ones in today’s galaxies. I will discuss state-of-the-art large-scale simulations which attempt to study directly the growth of the first, rare, supermassive black holes within the context of our standard structure formation models.

Qubit-Coupled Mechanics – Matt LaHaye Mon. October 22nd, 2012
12:30 pm-1:30 pm

There is a rapidly growing effort to integrate quantum technologies with mechanical structures in order to manipulate and measure quantum states of mechanics for applications ranging from quantum computing to sensing of weak forces to fundamental explorations of quantum mechanics at massive scales. A central focus of this effort, informally dubbed quantum electromechanical systems, has been the integration of superconducting electronics as control and measurement elements in nano and microelectromechanical systems (NEMS and MEMS). In fact, in just the last few years, spectacular advancements have been made in this area, providing researchers with a suite of tools for preparing, manipulating and measuring NEMS and MEMS near and even in the quantum domain.

Michelson Postdoc Prize talk 3:Many-body interactions in two-dimensional crystals – KinFai Mak Fri. October 19th, 2012
12:30 pm-1:30 pm

The problem of electrons in 2D is one of the most important topics in contemporary condensed matter physics. Coulomb interactions between charge carriers in 2D are dramatically enhanced with the much-reduced dielectric screening compared to their bulk counterpart. Recent advances in the development of atomically thin layers of materials have opened up new opportunities for the study of many-body effects in 2D. In the last talk, we will discuss the observations of strong excitonic effects in graphene and in a valley Hall semiconductor through optical spectroscopy. We will demonstrate the control of Coulomb interactions in such atomic membranes by tuning their dielectric screening through an electrostatic gate.

Manybody interactions in two-dimensional crystals – Kin Fai Mak Fri. October 19th, 2012
2:30 pm-3:30 pm

The problem of electrons in 2D is one of the most important topics in contemporary condensed matter physics. Coulomb interactions between charge carriers in 2D are dramatically enhanced with the much-reduced dielectric screening compared to their bulk counterpart. Recent advances in the development of atomically thin layers of materials have opened up new opportunities for the study of many-body effects in 2D. In the last talk, we will discuss the observations of strong excitonic effects in graphene and in a valley Hall semiconductor through optical spectroscopy. We will demonstrate the control of Coulomb interactions in such atomic membranes by tuning their dielectric screening through an electrostatic gate.

Beyond graphene: band insulators and topological insulators – Kin Fai Mak Thu. October 18th, 2012
4:15 pm-5:15 pm

Beyond graphene there exist a rich family of two-dimensional crystals with a broad spectrum of electronic properties, which remain largely unexplored. For instance, a valley Hall semiconductor emerges by breaking the sublattice symmetry in the honeycomb structure. I will present our recent study of monolayer molybdenum disulfide as a protocol. The observation of an indirect-to-direct band gap crossover in the 2D limit and the optical orientation of its long-lived coupled valley-spins will be discussed. Furthermore, in some of the small-band-gap semiconductors with strong spin-orbit coupling, a new insulating phase with topologically protected surface states appears, due to inverted conduction and valence orbitals.

Beyond graphene: band insulators and topological insulators – Kin Fai Mak Thu. October 18th, 2012
4:15 pm-5:15 pm

Beyond graphene, there exists a rich family of two-dimensional crystals with a broad spectrum of electronic properties, which remain largely unexplored. For instance, a valley Hall semiconductor emerges by breaking the sublattice symmetry in the honeycomb structure. I will present our recent study of monolayer molybdenum disulfide as a protocol. The observation of an indirect-to-direct band gap crossover in the 2D limit and the optical orientation of its long-lived coupled valley-spins will be discussed. Furthermore, in some of the small band gap semiconductors with strong spin-orbit coupling, a new insulating phase with topologically protected surface states appears due to inverted conduction and valence orbitals.

Michelson Postdoc Prize talk 2:Optics with Dirac electrons – KinFai Mak Tue. October 16th, 2012
12:30 pm-1:30 pm

Optical spectroscopy provides an excellent means of understanding the distinctive properties of electrons in the two-dimensional system of graphene. Within the simplest picture, one has a zero-gap semiconductor with direct transitions between the well-known conical bands. This picture gives rise to a predicted frequency-independent absorption of \pi\alpha = 2.3%, where \alpha is the fine-structure constant. We will demonstrate that this relation is indeed satisfied in an appropriate spectral range in the near infrared, but that at higher photon energies electron-hole interactions significantly modify this result through the formation of saddle-point excitons. Optical spectroscopy also permits a detailed analysis of how the linear bands of graphene,

Optics with Dirac electrons – Kin Fai Mak Tue. October 16th, 2012
12:30 pm-1:30 pm

Optical spectroscopy provides an excellent means of understanding the distinctive properties of electrons in the two-dimensional system of graphene. Within the simplest picture, one has a zero-gap semiconductor with direct transitions between the well-known conical bands. This picture gives rise to a predicted frequency-independent absorption of pi alpha = 2.3 %, where alpha is the fine-structure constant. We will demonstrate that this relation is indeed satisfied in an appropriate spectral range in the near infrared, but that at higher photon energies electron-hole interactions significantly modify this result through the formation of saddle-point excitons. Optical spectroscopy also permits a detailed analysis of how the linear bands of graphene,

Michelson Postdoc Prize talk 1:Novel two-dimensional systems: graphene and beyond – KinFai Mak Mon. October 15th, 2012
12:30 pm-1:30 pm

The past few years have witnessed a surge of activities in the study of graphene, a stable sheet comprised of just a single atomic layer of carbon atoms in a honeycomb lattice structure. Indeed, 2010 Nobel Physics Prize recognized two researchers for their pioneering contributions to this field. In this talk we will describe the development of the field and some of the reasons for the intense interest in this new material system, highlighting its unusual electronic dispersion and its distinctive mechanical and chemical properties. We will also discuss recent advances in the fabrication and investigation of other 2D atomic membranes.

Novel two-dimensional systems: graphene and beyond – Kin Fai Mak Mon. October 15th, 2012
4:15 pm-5:15 pm

The past few years have witnessed a surge of activities in the study of graphene, a stable sheet comprised of just a single atomic layer of carbon atoms in a honeycomb lattice structure. Indeed, 2010 Nobel Physics Prize recognized two researchers for their pioneering contributions to this field. In this talk we will describe the development of the field and some of the reasons for the intense interest in this new material system, highlighting its unusual electronic dispersion and its distinctive mechanical and chemical properties. We will also discuss recent advances in the fabrication and investigation of other 2D atomic membranes.

Gamma-ray Pulsars with the Fermi Gamma-ray Space Telescope [joint with Astronomy] – David J. Thompson Thu. October 11th, 2012
4:15 pm-5:15 pm

Pulsars, which are rapidly rotating magnetized neutron stars, are natural laboratories for physics under extreme conditions. Gamma radiation has now been seen from more than 100 pulsars, thanks to observations with the Large Area Telescope on the Fermi Gamma-ray Space Telescope. Found in approximately equal numbers are three types of gamma-ray pulsars: young radio-loud pulsars, young radio-quiet pulsars, and older millisecond pulsars. Fermi observations have also led to the discovery of new radio pulsars. This talk will present an overview of the Fermi observatory, how gamma-ray pulsars are found, what we have learned about these energetic objects, and how you might discover a gamma-ray pulsar.

Kicking Chameleons: Early Universe Challenges for Chameleon Gravity – Adrienne Erickcek Tue. October 9th, 2012
11:30 am-12:30 pm

Chameleon gravity is a scalar-tensor theory that mimics general relativity in the Solar System. The scalar degree of freedom is hidden in high-density environments because the effective mass of the chameleon scalar depends on the trace of the stress-energy tensor. In the early Universe, when the trace of the stress-energy tensor is nearly zero, the chameleon is very light and Hubble friction prevents it from reaching its potential minimum. Whenever a particle species becomes non-relativistic, however, the trace of the stress energy tensor is temporarily nonzero, and the chameleon begins to roll. I will show that these “kicks” to the chameleon field have catastrophic consequences for chameleon gravity.

Multiferroic vortices in hexagonal manganites – Weida Wu Mon. October 8th, 2012
12:30 pm-1:30 pm

Topological defects are pervasive in complex matter such as superfluids, liquid crystals, and early universe. They have been fruitful playgrounds for many emergent phenomena. Recently, vortex-like topological defects with six interlocked structural antiphase and ferroelectric domains merging into a vortex core were revealed in multiferroic hexagonal manganites. Numerous vortices are found to form an intriguing self-organized network, and may be used to test Kibble-Zurek model of early universe. Furthermore, emergent conduction and piezoelectric properties were observed in charged ferroelectric domain walls protected by topological defects. More excitingly, unprecedented alternating uncompensated magnetic moments were discovered at coupled antiferromagnetic-ferroelectric domain walls in hexagonal manganites,

Decades of Achievement — a tribute to nine of our number having birthdays ending in a zero – Various Thu. October 4th, 2012
4:15 pm-5:15 pm

Three physics faculty have their 50th birthday this year, three have their 60th, and three their 80th. We celebrate their achievements in this mini-symposium.

A new window on primordial non-Gaussianity – Enrico Pajer Tue. October 2nd, 2012
11:30 am-12:30 pm

We know very little about primordial curvature perturbations on scales smaller than about a Mpc. I review how mu-type distortion of the Cosmic Microwave Background spectrum provides the unique opportunity to probe these scales over the unexplored range from 50 to $104 Mpc-1$. This is a very clean probe, in that it relies only on well-understood linear evolution. While mu-distortion by itself can constrain the amount of power on small scales, correlations between mu-distortion and temperature anisotropies can be used to test Gaussianity. In particular the muT cross correlation is proportional to the very squeezed limit of the primordial bispectrum and hence measures $f_NL$ local,

Into the flat land: Transport studies of ultra-dilute GaAs two-dimensional hole systems in zero field – Jian Huang Mon. October 1st, 2012
12:30 pm-1:30 pm

Low temperature charge transport studies of high purity electron systems encompass fundamental subjects of disorder and electron-electron interaction. 50 years after Anderson’s theory of localization for non-interacting electrons, the question on whether and how electron-electron interaction qualitatively alters the picture is still unsettled. Fascinating subjects on interaction-driven phenomena such as Wigner crystallization of electrons (for the quantum scenario) have never been demonstrated. Experimentally, high-purity semiconductor bulk materials offer a desirable tunability of charge density down to ultra-dilute limits where both new frontiers of physics and important applications such as quantum information technologies can be explored. However, such a transition is often overshadowed by the substantial disorder which competes with or even dominates over interaction by rendering the system into an Anderson insulator.

“How we fixed the Hubble Space Telescope” – James Breckinridge Thu. September 27th, 2012
4:15 pm-5:15 pm
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) – a new tool to probe the dark energy driven expansion history of the universe from z=1-3 – Matt Dobbs Tue. September 25th, 2012
11:30 am-12:30 pm

The most surprising discovery in cosmology since Edwin Hubble observed the expansion of the Universe isthat the rate of this expansion is accelerating. This either signals that a mysterious Dark Energy dominatesthe energy density of the Universe, or that our understanding of gravity on large scales is incorrect. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) will produce the largest volume astronomical survey to date, potentially unlocking the mysteries the dark-energy driven expansion history of the Universe. The CHIME telescope forms an image of the entire over-head sky each night by digitally processing the information received on a compact array of 2500 radio receivers.

Valley-Electronics in 2D Crystals – Di Xiao Mon. September 24th, 2012
12:30 pm-1:30 pm

In many crystals the Bloch bands have inequivalent and well separated energy extrema in the momentum space, known as valleys. The valley index constitutes a well-defined discrete degree of freedom for low-energy carriers that may be used to encode information. This has led to the concept of valleytronics, a new type of electronics based on manipulating the valley index of carriers. In the first part of the talk, I will describe a general scheme based on inversion symmetry breaking to control the valley index, using graphene and monolayers of MoS2 as an example. In particularly, the valley Hall effect and valley-dependent optical selection will be discussed.

Non-Gaussianity from general inflationary states – Nishant Agarwal Tue. September 18th, 2012
11:30 am-12:30 pm

I will describe the effects of non-trivial initial quantum states for inflationary fluctuations within the context of the effective field theory for inflation. We find that besides giving rise to large non-Gaussianities from inflation, general initial states can also have interesting implications for the consistency relation of the bispectrum. In addition, they leave a distinct observable signature on the scale-dependence of the bias of dark matter halos. I will also discuss constraints on the initial state from current large scale structure data, including luminous red galaxies and quasars in the Sloan Digital Sky Survey sample.

Novel Ferroelectric Polymers as High Energy Density and Low Loss Dielectrics – Lei Zhu Mon. September 17th, 2012
12:30 pm-1:30 pm

The state-of-the-art polymer dielectrics have been limited to nonpolar polymers with relatively low energy density and ultra low dielectric losses for the past decades. With the fast development of power electronics in pulsed power and power conditioning applications, there is a need for next generation dielectric capacitors in areas of high energy density/low loss and/or high temperature/low loss polymer dielectrics. Given limitations in further enhancing atomic and electronic polarizations for polymers, this perspective article focuses on a fundamental question: Can orientational polarization in polar polymers be utilized for high energy density and low loss dielectrics? Existing experimental and theoretical results have suggested the following perspectives.

Gate Controlled Spin-Orbit Interaction and 1D Thermoelectric Transport in InAs Nanowires – Xuan Gao Thu. September 13th, 2012
4:15 pm-5:15 pm

InAs nanowires provide an interesting nanomaterial platform for spintronic device and thermoelectric energy conversion applications, owing to their strong quantum confinement and spin orbit interaction (SOI) effects. Manipulating the SOI and thermoelectric transport in InAs nanowires is thus of great interest for both fundamental quantum transport and applied nanotechnology research. First, we will discuss our recent results of gate induced generation and control of the Rashba SOI (a momentum dependent splitting of spin bands) in InAs nanowires, which is essential for the realization of many spintronic devices. Second, we present a study of the thermoelectric properties of InAs nanowires where the gate was used to sweep the electrons’

Boosting the Universe: Observational consequences of our motion – Amanda Yoho Tue. September 11th, 2012
11:30 am-12:30 pm

The Cosmic Microwave Background (CMB), photons from the earliest epoch that are able to free stream towards us, provides a unique opportunity to learn about many properties of the universe we live in. Already, the temperature fluctuations of the CMB have been studied by the Wilkinson Anisotropy Probe (WMAP) and have allowed many cosmological parameters to be pinned down to within a percent error. However, there are many more mysteries to be uncovered by precise measurements of the CMB polarization of these photons and weak lensing fields. Only with a robust understanding of the possible contaminants and astrophysical effects that can deform the measured fields will we be able to accurately characterize which models are favored over others.

Interfacial Charge Transfer in Nanomaterial Based Light Harvesting Devices – Mat Sfire Mon. September 10th, 2012
12:30 pm-1:30 pm

We purposefully design and study “molecular-like” interfacial interactions between the multidimensional nanometer-scale building blocks that compose larger-scale functional light harvesting devices. Using time-resolved optical spectroscopy, we aim to understand the nature of discrete interfacial electronic states and their role as crucial intermediates promoting efficient interactions between extended systems (e.g., charge transfer). Our research has suggested the importance of such intermediate interfacial states in both hard and soft nanomaterial heterostructures, including semiconductor quantum dots and organic semiconductors. We aim to understand the fundamental impact of “molecular-like” interfacial states on macroscopic material properties, such as charge transport and light harvesting. For example,

The Intersection between Science and Politics: How Science is Used and Abused in Congress – Chris Martin Thu. September 6th, 2012
4:15 pm-5:15 pm

After spending a year working as a staffer in the US Senate’s Commerce, Science, and Transportation Committee, Dr. Chris Martin of Oberlin College brings a scientist’s perspective to how national policy reacts to and in turn drives science. Using examples covering the range of congressional interests, including climate change, earthquakes, human space exploration, and nanotechnology, Dr. Martin shows how politicians and scientists can communicate about issues in completely different ways leading to humorous conflicts and surprising synergies. If you have ever wondered what happens in the halls of Congress and how you can most effectively make a difference, this is a talk you should not miss!

The interplay between high and low redshift universe – Azadeh Moradinezhad Dizgah Tue. September 4th, 2012
11:30 am-12:30 pm

Download the slides

Development of the II-IV Nitride Semiconductors; Considerations from Science, Technology and Sociology – Kathy Kash Thu. August 30th, 2012
4:15 pm-5:15 pm

Ever since the profound effect of the invention of the transistor in 1947, the impact of inorganic semiconductors on our technology world has continued to expand. The III-nitrides (GaN, AlN and InN) are a current example of a class of semiconductors that is increasing ‘exponentially’ in its impact on technology. While the II-IV nitrides are intimately related to the III-nitrides, to date surprisingly little research has been done on the former. Using recent results, the context of the III-nitrides, and focusing in particular on band gaps, structural characterization and phonon properties, I will attempt to convince you that the II-IV-nitrides are of scientific interest,

Supersymmetry, Naturalness, and the LHC: Where Do We Stand? – Matthew Reece Tue. May 1st, 2012
11:30 am-12:30 pm

The LHC has accumulated a large luminosity and has already begun ruling out a wide range of theoretical scenarios. I will discuss the theoretical implications of current LHC searches for supersymmetry and the first tentative Higgs measurements. In particular, I will assess the current status of SUSY naturalness, and explain some ways in which searches for the scalar top quark might help to further constrain the parameter space.

Optical Material Science: Electrodynamics of Nanoscale Assembly, and Lifetime and Degradation Science for Photovoltaics – Roger H. French Mon. April 30th, 2012
12:30 pm-1:30 pm

The optical properties and electronic structure of materials are critical to the development of new optical materials,(1) novel processes of nanoscale assembly, and the viability of advanced energy technologies. They are the origin of the electrodynamic van der Waals-London dispersion (vdW-Ld) interactions (2) which play a universal role in wetting, interfacial energies, and nanoscale assembly.(3) The challenge of nanotechnology is for science to span more than nine orders of magnitude in dimension. Advanced energy technologies, with their 25 or 50 year capital lifetimes, challenge us to span 24 orders of magnitude in time so as to control degradation processes, damage accumulation,

Smectics! – Randall Kamien Thu. April 26th, 2012
4:15 pm-5:15 pm

The homotopy theory of topological defects in ordered media fails to completely characterize systems with broken translational symmetry. I will demonstrate that the topological problem can be transformed into a geometric problem in one higher dimension. Fortunately, for two-dimensional smectics this amounts to the theory of surfaces in three space! Our work suggests natural generalizations of the two-dimensional smectic theory to higher dimensions and to crystals.

Gravitational Wave Detection with Pulsars: the NANOGrav collaboration – Dan Stinebring Tue. April 24th, 2012
11:30 am-12:30 pm

The effort to detect long-wavelength gravitational waves with a pulsar timing array (PTA) is progressing well, with three major international groups intensifying their efforts and increasingly sharing data and techniques. *Your* PTA, the North American Nanohertz Observatory for Gravitational waves (NANOGrav) is making excellent progress. I will report on our recent results and also comment on my group’s specialty, the effort to remove time variable propagation delays through the ionized interstellar medium.

Magnetoresistance in Two Dimensions – Arnold J. Dahm Mon. April 23rd, 2012
12:30 pm-1:30 pm

We present measurements of the magnetoresistivity of a weakly interacting 2D electron liquid in an unexplored region near the boundary of the 2D electron gas supported by a liquid helium surface. The magnetoresistivity is calculated by Dykman in the self-consistent Born approximation. For fields greater than a field B0, the magnetoresistivity is proportional to (muB)^3/2, where mu is the mobility. Electron-electron interactions cause a crossover to the Drude behavior as the density is increased. All of our data scale with the density-dependent parameter B0 as B/B0, with the magnitude of the magnetoresistivity scaled as 1/n. For low electron densities and fields less that B0,

Combining superconductors and ferromagnets: a new type of symmetry? – Norman Birge Thu. April 19th, 2012
4:15 pm-5:15 pm

Physicists are constantly on the lookout for new symmetries in the ground states of quantum systems. Familiar examples include ferromagnets, which break spin-rotation symmetry, and superconductors, which break gauge symmetry. When a superconductor (S) and a ferromagnet (F) are put into contact with each other, interesting things happen, and the combined S/F hybrid system exhibits altogether new properties. There is a proximity effect where pair correlations from S penetrate into F, but this proximity effect decays over a very short distance due to the large energy splitting between the spin-up and spin-down electrons. Theory predicts that, under certain conditions, electron pair correlations will appear with spin-triplet rather than spin-singlet symmetry [1].

Hunting for de Sitter vacua in the String Landscape – Gary Shiu Tue. April 17th, 2012
11:30 am-12:30 pm

Results from observational cosmology suggest that our universe is currently accelerating. The simplest explanation is that we are living in a universe with a positive cosmological constant. In this talk, I will describe some recent attempts in constructing such solutions in string theory and discuss the difficulties one encounters in finding metastable de Sitter vacua. Thus, the requirement of positive cosmological constant and stability imposes strong constraints on the string theory landscape.

Electronic structure of disordered solids – David A. Drabold Mon. April 16th, 2012
12:30 pm-1:30 pm

Understanding the physics of structurally disordered materials is a challenge to experimentalists and theorists alike. In this talk, I discuss the character of electronic states in disordered materials and emphasize the interplay between structure and electronic properties. I begin by discussing the consequences of atomic structural disorder on electron states. As shown long ago by Anderson, disorder in atomic coordinates creates spatially confined or “localized” electron eigenstates near the Fermi level. I explore these states with large and realistic structural models and suitable electronic structure techniques. I begin with the structure of electron states in large and realistic models of a-Si,

Stars, galaxies and cosmology in the nearby Universe [joint with Astronomy] – Alan McConnachie Thu. April 12th, 2012
4:15 pm-5:15 pm

The basic tenets of the prevailing cosmological paradigm – Lambda-Cold Dark Matter – are generally well understood and robust to large scale observables, such as the cosmic microwave background and galaxy clustering. The past few years has seen the focus of cosmological studies shift into a new “precision” regime. Modern simulations of galaxy formation are very successful at using our current, incomplete, understanding of baryonic evolutionary processes to provide testable predictions about the small scale distribution of mass and light in and around galaxies. The onus, therefore, is to obtain data which will provide critical tests of the models on galactic scales and hence advance these important cosmological theories.

Bosonic and Fermionic Non-thermal Dark Matter Isocurvature Perturbations and Non-Gaussianities – Daniel Chung Tue. April 10th, 2012
11:30 am-12:30 pm

Dark matter candidates in a broad class of non-thermal models produce primordial isocurvature perturbations and non-Gaussianities. We discuss the model dependence of such scenarios. In particular, fermionic superheavy dark matter requires non-gravitational interactions to be observationally interesting. We also present a general mathematical result regarding the cross correlation between the primordial isocurvature perturbations and curvature perturbations. This last result is of general interest for isocurvature phenomenology. Download the slides

Lasers and Anti-lasers – A. Douglas Stone Thu. April 5th, 2012
4:15 pm-5:15 pm

A laser is an optical device that transforms incoherent input energy (the pump), into coherent outgoing radiation in a specific set of modes of the electromagnetic field, with distinct frequencies. There is a threshold pump energy for the first lasing mode, and above that energy the laser is a non-linear device, and non-linear interactions strongly affect the emission properties of the laser. Surprisingly, the electromagnetic theory of non-linear steady-state multimode lasing remained rather rudimentary until recently. Motivated by the complex laser cavities being developed in modern micro and nano-photonics, we have developed a new formalism, Steady-state Ab initio Laser Theory (SALT),

Ghost-free multi-metric interactions Tue. April 3rd, 2012
11:30 am-12:30 pm

The idea that the graviton may be massive has seen a resurgence of interest due to recent progress which has overcome its traditional problems. I will review this recent progress, and show how the theory can be extended to write consistent interactions coupling together multiple massive spin-2 fields. Download the slides

The role of molecular beam epitaxy in fundamental physics through an example: assessing the impact of disorder on the v=5/2 fractional quantum Hall effect – Mike Manfra Fri. March 30th, 2012
11:30 am-12:30 pm

Thirty years after its initial discovery, the fractional quantum Hall effect continues to challenge our understanding of electronic correlations in low dimensions. Throughout this history advances in molecular beam epitaxy (MBE) have played an important role. Presently, the fragile v=5/2 fractional quantum Hall state is the subject of intense scrutiny. It is theoretically conjectured that the v=5/2 state is described by the Moore-Read Pfaffian wavefunction, possessing excitations obeying non-Abelian braiding statistics. If experimentally confirmed, excitations with non-Abelian braiding statistics may provide a platform for proposed schemes of topologically-protected quantum computing. While there are many aspects to the physics at v=5/2,

The Life and Death of a Drop: Topological Transitions and Singularities – Sidney Nagel Thu. March 29th, 2012
4:15 pm-5:15 pm

Because fluids flow and readily change their shape in response to small forces, they are often used to model phenomena as diverse as the dynamics of star formation or the statics of nuclear shape. Moreover, fluids can easily break apart and thus are also an excellent starting point for investigating topological transitions. Although part of our common everyday experience, these transitions are far from understood. In this lecture, I will give the life history of a liquid drop – from its birth as a pendant fluid to its eventual demise, after splashing, as it vanishes into air. During its brief life,

Chromo-Natural Inflation – Peter Adshead Tue. March 27th, 2012
11:30 am-12:30 pm

I will describe a new model for inflation – Chromo-Natural Inflation – consisting of an axionic scalar field coupled to a set of three non-Abelian gauge fields. The model’s novel requirement is that the gauge fields begin inflation with a rotationally invariant vacuum expectation value (VEV) that is preserved through identification of SU(2) gauge invariance with rotations in three dimensions. The gauge VEV interacts with the background value of the axion, leading to an attractor solution that exhibits slow roll inflation even when the axion decay constant has a natural value (\less M_{\rm Pl}). Assuming a sinusoidal potential for the axion,

Micro and Nano Technology at the Lurie Nanofabrication Facility – Robert Hower Fri. March 23rd, 2012
12:30 pm-1:30 pm

This seminar will give an overview of micro and nano technologies at the University of Michigan Lurie Nanofabrication Facility (LNF). In addition, we will present examples of research accomplishments and applications of these technologies in diverse fields including but not limited to Electrical Engineering, Physics, Life Sciences, Biomedical Engineering and Chemical Engineering.
Operated by the University of Michigan Solid-State Electronics Laboratory (SSEL), the LNF has extensive experience in microelectronics, micromechanics, optoelectronics, and micro and nano technologies based on silicon, compound semiconductor, and organic materials. It offers a complete laboratory for the fabrication of nanofabricated semiconductor and polymer electronic and optoelectronic devices and circuits,

Multilayer Polymer Photonics: From “Origami” Lasers to Optical Data Storage to Cavity Polaritons – Ken Singer Thu. March 22nd, 2012
4:15 pm-5:15 pm

The National Science Foundation Center for Layered Polymer Systems (CLiPS), in its sixth year at CWRU, is focused on a novel multilayer co-extrusion technique, which is a highly scalable roll-to-roll process capable of producing many square meters of periodic layered films in minutes. Co-extruded polymer films already have a number of applications, and research is now aimed at exploring optical and electronic phenomena and applications. Depending on the layer dimensions and periodicity, these films could act as gradient refractive index materials, photonic crystals, and other optical multilayer structures. Of particular interest is imparting to one of the layer types such functions as stimulated emission,

Testing the concordance cosmology with weak gravitational lensing – Ali Vanderveld Tue. March 20th, 2012
11:30 am-12:30 pm

Weak gravitational lensing, whereby the images of background galaxies are distorted by foreground matter, can be a powerful cosmological probe if systematics are sufficiently controlled. In particular, I will show how we may use weak lensing to robustly test the standard cosmological constant-dominated “concordance model” of cosmology by using in-hand expansion history data to make predictions for future observations. I will then discuss one recent proposal for economically gathering the necessary data while minimizing systematics — the balloon-borne High Altitude Lensing Observatory (HALO). Download the slides

Anisotropic response in molecular crystals and the development of Modulated Orientation Sensitive Terahertz Spectroscopy (MOSTS) – Andrea Markelz Mon. March 19th, 2012
12:30 pm-1:30 pm

Since the mid 1980’s there have been predictions of protein structural vibrations with ~ 1meV energies, which corresponds to the terahertz frequency range. These large scale motions involve the correlated movement of many atoms and are associated with the conformational motions involved in protein function. There have been many attempts to measure these modes, but the energy range overlaps with that of local librational motions of the surface side chains and the solvent, and these contributions give rise to a strong glass-like response. In this talk I will discuss our development of a technique to isolate the large scale structural contribution from a glassy background called Modulated Orientation Sensitive Terahertz Spectroscopy (MOSTS).

III-Nitride Light-Emitting Diodes for Solid-State Lighting – Hongping Zhao Mon. March 12th, 2012
12:30 pm-1:30 pm

Energy efficiency and renewable energy technologies have significant importance for achieving sustainable energy systems in modern society. Lighting accounts for more than 22% of the total electrical energy usage in US, and technologies based on solid state lighting (SSL) utilizing semiconductor-based material has tremendous promise to replace the existing lighting devices. As compared to traditional incandescent and fluorescent lamps, SSL is more energy-efficient, reliable, and environmentally-friendly. Once widely used, SSL could lead to the decrease of worldwide electricity consumption for lighting by >50% and reduces total electricity consumption by >10%. The U.S. Department of Energy describes SSL as a pivotal emerging technology that promises to fundamentally alter lighting in the future.

The Red Revolution: How Seismology of Red Giants is Transforming Stellar Physics and Stellar Population Studies [joint with Astronomy] – Marc Pinsonneault Thu. March 8th, 2012
4:15 pm-5:15 pm

Space missions have uncovered a rich, and high amplitude, pulsation spectrum in red giant stars. The information encoded in the pulsation frequencies is transforming our understanding of stars. At one level, crucial information (such as mass, radius, and age) can be used for stellar population studies. At another, we can make critical tests of stellar physics with new seismic observables (such as core rotation, convection zone depth, and core mass.) In this talk I begin by reviewing the pulsation properties of giants. I’ll then cover the likely cause of the observed frequency patterns, highlighting the role of strong coupling between core g-modes and envelope p-modes.

HgTe as a Topological Insulator – Laurens Molenkamp Mon. March 5th, 2012
12:30 pm-1:30 pm

HgTe is a zincblende-type semiconductor with an inverted band structure. While the bulk material is a semimetal, lowering the crystalline symmetry opens up a gap, turning the compound into a topological insulator. The most straightforward way to do so is by growing a quantum well with (Hg,Cd)Te barriers. Such structures exhibit the quantum spin Hall effect, where a pair of spin polarized helical edge channels develops when the bulk of the material is insulating.
Our transport data provide very direct evidence for the existence of this third quantum Hall effect, which now is seen as the prime manifestation of a 2-dimensional topological insulator.

An estimator for statistical anisotropy from the CMB bispectrum – Ema Dimstrogiovanni Tue. February 28th, 2012
11:30 am-12:30 pm

Various data analysis of the Cosmic Microwave Background (CMB) radiation present anomalous features that can be interpreted as indications of statistical isotropy breaking. Some models of inflation involving vector fields predict statistical anisotropy in the correlation functions of primordial curvature perturbations. We employ a simplified vector field model and parametrize the bispectrum of curvature fluctuations in such a way that all the information about statistical anisotropy is encoded in some coefficients lambda_{LM} (representing the ratio of the anisotropic to the isotropic bispectrum amplitudes). We compute an optimal estimator for these coefficients and their Fisher error. We predict a sensitivity for an experiment like Planck to the anisotropic to isotropic amplitudes of about 10% if fNL is around 30.

Pollockian Mechanics: Painting with Viscous Jets – Andrzej Herczyński Thu. February 23rd, 2012
4:15 pm-5:15 pm

Beginning around 1945, an American Abstract Expressionist painter Jackson Pollock invented and perfected a new artistic technique based on pouring and dripping liquid pigment onto a canvas stretched horizontally on the floor. In so doing, he creatively engaged fluid phenomena, in effect inviting physics to co-author his pieces. Long recognized as important and influential by art historians, Pollock’s works, and the tangled webs he created, have recently received attention also from scientists. But although the artist manipulated gravitational flows to achieve his aims, the fluid dynamical aspects of his process remained largely unexplored. I will discuss Pollockian Mechanics-the physics of lifting paint by viscous adhesion and dispensing it in free jets-focusing on the role of fluid instability.

Local Primordial non-Gaussianity in Large-scale Structure – Marilena LoVerde Tue. February 21st, 2012
11:30 am-12:30 pm

Primordial non-Gaussianity is among the most promising of few observational tests of physics at the inflationary epoch. At present non-Gaussianity is best constrained by the cosmic microwave background, but in the near term large-scale structure data may be competitive so long as the effects of primordial non-Gaussianity can be modeled through the non-linear process of structure formation. I will discuss recent work modeling effects of a few types of primordial non-Gaussianity on the large-scale halo clustering and the halo mass function. More specifically, I will compare analytic and N-body results for two variants of the curvaton model of inflation: (i) a “tau_NL”

High Tc superconductivity in cuprates: A status report – Mohit Randeria Fri. February 17th, 2012
12:30 pm-1:30 pm

25 years after their discovery, the microscopic problem of high Tc superconductivity in cuprates is still not “solved”. I will focus on summarizing the experiments that show us that the observed phases, with varying carrier concentration, challenge three paradigms of 20th century condensed matter physics. (i) The parent Mott insulator cannot be understood within band theory; (ii) the superconducting state and phase transition force us to go beyond a BCS mean-field description; and (iii) the “normal” metallic state cannot be described within Landau Fermi liquid theory. I will then briefly describe some of the success in theoretically understanding the superconducting state and indicate open questions about the normal state.

Viscosity of Strongly Interacting Fermions – Mohit Randeria Thu. February 16th, 2012
4:15 pm-5:15 pm

The viscosity of strongly interacting quantum fluids has recently been examined in diverse areas of physics – black holes and string theory, quark-gluon plasmas and cold atoms – which, at first sight, appear to have little in common. In this colloquium, I will focus on the viscosity of ultracold Fermi gases, for which the most controlled experiments should be possible. I will begin with an introduction to the problem of viscosity of quantum systems and a review of the theoretical and experimental progress in exploring the BCS-BEC crossover of ultracold Fermi gases. I will then discuss connections between transport and thermodynamics across the entire crossover using exact sum rules,

Inflation, or What? – William Kinney Tue. February 14th, 2012
11:30 am-12:30 pm

Cosmological inflation is the leading candidate theory for the physics of the early universe, and is in beautiful agreement with current cosmological data such as the WMAP Cosmic Microwave Background measurement. I consider alternatives to inflation with a critical eye, and present a simple argument showing that any model which matches the observed universe must have one of three properties: (1) accelerated expansion, (2) speed of sound faster than the speed of light, or (3) super-Planckian energy density. Download the slides

Quantum Signatures of Optomechanical Instability and Synchronization in Optomechanical Arrays – Jiang Qian Mon. February 13th, 2012
12:30 pm-1:30 pm

Optomechanical systems couple light stored in an optical resonant cavity to the motion of a mechanical motion of the cavity walls. Single optomechanical cells have been successfully fabricated in a wide variety of systems. Recent experiments have further demonstrated setups, such as photonic crystal structures, that in principle allow to confine several optical and vibrational modes on a single chip.
In the first part of my presentation I will demonstrate the emergence of a robust, long-living and highly non-classical mechanical state in a standard single cell optomechanical setup. I will show that under some parameters, the longtime steady state of the mechanical degrees of freedom has significantly negative Wigner density.

The 2011 Science Nobel Prizes – What were they given for? – Glenn Starkman, Arthur Heuer, and Mansun Sy Thu. February 9th, 2012
4:15 pm-5:15 pm

GLENN STARKMAN (Dept. of Physics) will present on the Nobel Prize in Physics: The 2011 Nobel Prize in Physics was awarded to leaders of two collaborations that in 1998 discovered that the expansion of the universe is accelerating. We will review the evidence they presented for that claim, and briefly discuss possible explanations such as dark energy and modifications to the standard theory of gravity and General Relativity.

MAN-SUN SY (Dept. of Pathology) will present on the Nobel Prize in Medicine: Prof. Man-Sun will speak on the three recipients of the Nobel prize in Medicine in 2011. He will provide a little background regarding their original contributions,

Quantum Kinetics and Thermalization of Hawking Radiation – Dmitry Podolsky Tue. February 7th, 2012
11:30 am-12:30 pm

Hawking’s discovery of black holes radiance along with Bekenstein’s conjecture of the generalized second law of thermodynamics inspired a conceptually pleasing connection between gravity, thermodynamics and quantum theory. However, the discovery that the spectrum of the radiation is in fact thermal, together with the no-hair theorem, has brought along with it some undesirable consequences, most notably the information loss paradox. There have been many proposals to the resolution of this paradox, with the most natural resolution being that during the time of collapse the radiation given off is not completely thermal and can carry small amounts of information with it.

Condensates and quasiparticles in inflationary cosmology – Daniel Boyanovsky Mon. February 6th, 2012
11:30 am-12:30 pm

Correlation functions during inflation feature infrared effects that could undermine a perturbative study. I will discuss self-consistent mechanisms of mass generation that regulates infrared physics, and introduce a method based on quantum optics to obtain the decay width of quantum states. Lack of energy conservation entails that EVERY particle acquires a width as a result of emission and absorption of superhorizon quanta thus becoming “quasiparticles”. BLACKBOARD TALK

Fe pnictide superconductors – David Singh Mon. February 6th, 2012
12:30 pm-1:30 pm

The 2008 discovery of high temperature superconductivity in doped LaFeAsO by Kamihara and co-workers provided the second class of high Tc materials, the other being the cuprate family discovered in 1986 by Bednorz and Mueller. This discovery was revolutionary in that many of the properties of the iron based superconductors are radically different from those of the cuprates, apparently requiring a new and broader understanding of the physics of high temperature superconductivity. The purpose of this talk is to discuss the chemistry and physics of the new superconductors in relation to cuprates. So far, many puzzles remain. The materials appear to be much more band-like and show much stronger signatures of metallic (Fermi surface related) physics than cuprates,

Oriented assembly of microparticles by capillarity – Kate Stebe Thu. February 2nd, 2012
4:15 pm-5:15 pm

Particles with well defined shapes can be directed to assemble into complex structures by capillarity. Here we explore two themes. First, we explore the assembly of microparticles with well-defined shapes on otherwise planar interfaces to form structures with preferred orientations and with mechanical responses that depend subtly on particle shape. Progress in developing a quantitative understanding of pair interactions and mechanics of assemblies between rod-like particles is described and compared to experiment. Experiments using microparticles with a variety of particle shapes are presented to illustrate a range of possibilities including control over preferred face for assembly and the assembly of particles with complex features in registry.

Gravitational Waves from Cosmological Phase Transitions – Tom Giblin Tue. January 31st, 2012
11:30 am-12:30 pm

Cosmological phase transitions occurred. I will talk about recent advances in modeling possible phase transitions when these transitions are mediated by scalar fields. I will discuss first- and second-order transitions, at various scales, and show how we can compute the background of stochastic gravitational waves produced during (and after) these transitions.

The Incredible Shrinking Tuning Forks – Nanowire Electromechanical Systems at Radio and Microwave Frequencies – Philp Feng Mon. January 30th, 2012
12:30 pm-1:30 pm

Nanoscience today enables many fascinating low-dimensional structures and new materials with previously inaccessible properties. Nanostructures with mechanical degrees of freedom offer compelling characteristics that make them interesting for both fundamental studies and technological applications. This talk will describe my collaborative research efforts in exploring vibrating nanowires, and in engineering these very thin nanowires into functional and high-performance nanoscale electromechanical systems (NEMS). I will show NEMS resonators operating in the very-high and ultra-high frequency (VHF/UHF, 30MHz – 3GHz) ranges, based on silicon nanowires enabled by a hybrid bottom-up/top-down process. Exploiting the interesting properties of thin silicon nanowires, we have developed an all-electronic,

Higgs Boson – on the road to discovery – Sergo Jindariani Thu. January 26th, 2012
4:15 pm-5:15 pm

The Higgs boson is an important piece of the Standard Model of particle physics that has yet to be experimentally observed. I will give a short review of high energy colliders and particle detectors and will describe the challenges of discovering a Higgs boson with these machines. I will summarize the status of Higgs boson searches at the Tevatron Collider at Fermilab and the Large Hadron Collider at CERN and portray the excitement at these labs as we move forward towards the discovery of the Higgs.

Spatially Covariant Theories of a Transverse, Traceless Graviton – Godfrey Miller Tue. January 24th, 2012
11:30 am-12:30 pm

General relativity is a generally covariant, locally Lorentz covariant theory of two transverse, traceless graviton degrees of freedom. According to a theorem of Hojman, Kuchar, and Teitelboim, modifications of general relativity must either introduce new degrees of freedom or violate the principle of local Lorentz covariance. In this paper, we explore modifications of general relativity that retain the same graviton degrees of freedom, and therefore explicitly break Lorentz covariance. Motivated by cosmology, the modifications of interest maintain explicit spatial covariance. In spatially covariant theories of the graviton, the physical Hamiltonian density obeys an analogue of the renormalization group equation which encodes invariance under flow through the space of conformally equivalent spatial metrics.

Fundamental Physics from Large-Scale Structure – Dragan Huterer Thu. January 19th, 2012
4:15 pm-5:15 pm

A little more than a decade after the discovery of the accelerating universe, the nature of dark energy remains one of the greatest known yet unsolved problems in cosmology and physics. Ongoing and upcoming surveys of the cosmic microwave background and large-scale structure are excellent tools to understand dark energy. Nevertheless, it is now clear that this will be difficult, and patience in understanding dark energy may be required as I will explain. I will then review some other aspects of fundamental physics that will be sharply probed by large-scale structure. In particular, I will talk about current and future constraints on cosmological inflation using measurements of primordial non-Gaussianity and statistical isotropy of density fluctuations in the universe.

Can that really be so? A light-hearted look at the concept of force in classical, quantum, and statistical mechanics – Philip Taylor Thu. December 8th, 2011
4:15 pm-5:15 pm

Some folk think that there are four types of force. Napoleon thought there were two. I am going to talk about three types. Of these, the most interesting by far is the entropic force, which is the one that drives us to explore the unknown. Along the way, we will reach some remarkable conclusions. But will they stand up to scrutiny? As a clue we mention that the word scrutiny itself comes from the Latin for “those who search through piles of trash in the hope of finding something of value.” Do come and scrute with us at the last colloquium of the semester.

Graphene Optics and Electronics – Marcus Freitag Mon. December 5th, 2011
12:30 pm-1:30 pm

Graphene is a two-dimensional material with conical bands that touch at the Dirac or Charge-Neutrality point. Its zero bandgap and atomically thin body allow it to switch between n-type and p-type conduction when assembled into a field-effect transistor geometry. The current modulation however is limited due to a finite minimum conductivity at the Charge Neutrality point, which prevents us from using graphene for digital electronic applications.
We therefore investigate graphene as an optical and analog electronic material, where the low on-off ratio is less of a problem. Especially the high frequency (RF) electronic applications are promising since graphene can be gated efficiently and has high carrier mobility.

Dark matter bounds from direct and indirect searches – Aravind Natarajan Tue. November 22nd, 2011
11:30 am-12:30 pm

I discuss ways of constraining dark matter properties using a combination of direct and indirect dark matter measurements. The DAMA, CoGeNT, and CRESST experiments have obtained tentative evidence for low mass WIMPs. I show that the CMB is a clean probe of low mass WIMPs, and the WMAP+SPT measurements place competitive bounds on light WIMPs. I discuss how these dark matter bounds may be further improved by including other data sets, such as counts of galaxy clusters.

Charge carrier dynamics in heterostructured semiconductor nanocrystals and nanocrystal solids – Michail Zamkov Mon. November 21st, 2011
12:30 pm-1:30 pm

In the first part, I will present a novel strategy for processing of colloidally stable semiconductor nanoparticles (also known as nanocrystals or quantum dots) into all-inorganic solid films, deployable for photovoltaic applications. The method relies on encapsulation of semiconductor nanocrystal arrays within a matrix of a wide-band gap inorganic material, which preserves optoelectronic properties of individual nanoparticles, yet, renders the nanocrystal film photoconductive. The photovoltaic performance of fabricated nanocrystal solids is demonstrated through the development of prototype solar cells exhibiting stable and efficient operation in ambient conditions.
The second part of the presentation will focus on ultrafast electron processes taking place in heterostructured nanocrystals comprising metal (Au) and semiconductor (CdS) material domains.

Closing In On Dark Matter – Dan Hooper Thu. November 17th, 2011
4:15 pm-5:15 pm

A variety of direct and indirect searches for dark matter are currently underway, a number of which have even reported observations which could be interpreted as hints of a signal. In this talk, I will discuss why particle physicists think that dark matter is likely to be made up of WIMPs, and how experiments are finally reaching the sensitivities needed to test the WIMP-hypothesis. If dark matter is, in fact, made up of WIMPs, then it seems likely that at least some of the search strategies being employed will be successful in the coming few years. If not, their null results are going to make it increasingly difficult to build viable particle dark matter models.

Light does not always travel on the light cone – Yi-Zen Chu Tue. November 15th, 2011
11:30 am-12:30 pm

Massless particles such as photons and gravitons do not travel solely on the null cone in a generic curved spacetime. They propagate at all speeds equal to and less than c. This fact does not appear to be well appreciated in cosmology, and its consequences deserve to be worked out to ensure we are interpreting observations correctly. A rather dramatic (and hypothetical) example would be the following: suppose a significant fraction of photons from a distant supernova travels slower than c, then we may be mislead into thinking the SN is dimmer than it actually is, because some of the light has not arrived yet.

A physicist walks into a biology department… – Robin Snyder Mon. November 14th, 2011
12:30 pm-1:30 pm

I present two recent projects in theoretical ecology and point out the connections to math loved by physicists. The first concerns life in a variable environment: when should an organism buffer itself against environmental variation and when should it try to take advantage of environmental variation? The second concerns the viability of mussel populations in a marine reserve network when shifting ocean currents cause fluctuating dispersal between reserves.

Holographic Quantum Quench – Sumit Das Fri. November 11th, 2011
11:30 am-12:30 pm

The holographic correspondence between non-gravitational field theories and gravitational theories in one higher dimension can be used to study non-equilibrium behavior of strongly coupled quantum field theories. One such phenomenon is that of quantum quench, where a coupling of the field theory is time dependent and typically asymptotes to constants at early and late times. In the gravity dual this can describe, under suitable circumstances, either black hole formation, or passage through a spacelilke region of high curvature similar to a cosmological singularity. On one hand this has taught us about the meaning of cosmological singularities, while on the other hand this has thrown light on the process of thermalization in strongly coupled field theories.

A Paradise Island for Deformed Gravity – Florian Kuehnel Tue. November 8th, 2011
11:30 am-12:30 pm

I will discuss our recently-proposed model (hep-th/1106.3566) of deformations of general relativity that are consistent and potentially phenomenologically viable, since they respect cosmological backgrounds. These deformations have unique symmetries in accordance with unitarity requirements, and give rise to a curvature induced self-stabilizing mechanism. Furthermore, our findings include the possibility of consistent and potentially phenomenologically viable deformations of general relativity that are solely operative on curved spacetime geometries, reducing to Einstein’s theory on the Minkowski background. I will also comment on possible phenomenological implications.

The search for Majorana Fermions in semiconductor nanowires – Roman Lutchyn Mon. November 7th, 2011
12:30 pm-1:30 pm

The exploration of topological phases of matter is one of the main challenges in condensed matter physics. Among the exciting recent developments in this direction are the discoveries of the new phases of matter with many intriguing properties such as topological insulators and superconductors. In my talk, I will focus on topological superconductors and discuss how to realize spinless p-wave superconductivity in semiconductor/superconductor heterostructures. I will show that such a non-trivial topological state emerging at the interface supports zero-energy modes that can be occupied by Majorana fermions. These quasi-particles, which are exotic in the sense that they are at the same time their own antiparticles,

Computational Thermodynamics: First Principles Prediction of Crystal Structures and Alloy Phase Diagrams – Michael Widom Thu. November 3rd, 2011
4:15 pm-5:15 pm

As Feynman noted, rules of chemistry are determined “in principle” by physics, but just as knowing the rules of chess do not immediately make one a great chess player, deriving chemistry from physics has challenged scientists for the past century. To predict thermodynamic properties of matter depends on two branches of physics: quantum mechanics, which governs the energetics and dynamics of elementary constituent particles; statistical mechanics, which deals with interactions of many particles and introduces the concept of temperature. This talk surveys new developments in computational thermodynamics that allow prediction of alloy phase diagrams and crystal structures truly from first principles.

Measuring the dark sector with clusters of galaxies – Douglas Clowe Tue. November 1st, 2011
11:30 am-12:30 pm

Since Zwicky (1933), we have known that clusters of galaxies have gravitational potentials which are too large to be explained by the amount of visible baryons under the assumption of a Newtonian gravitational force law. This has led to competing hypotheses that either the masses of clusters are dominated by a non-baryonic form of matter or that gravity departs from a 1/r^2 force law on cluster scales. By using merging clusters of galaxies, I will show that the different types of matter in the clusters can be spatially seperated and, by using gravitational lensing, I will prove, independent of any assumptions about the nature of the law of gravity,

Theoretical studies of magnetic and structural thermodynamics using effective Hamiltonians – Kirill Belashchenko Mon. October 31st, 2011
12:30 pm-1:30 pm

Effective configurational and spin Hamiltonians are commonly used to study magnetic and structural thermodynamics. For some purposes, such as the description of phase transitions in substitutional alloys, they can be routinely constructed by high-throughput first-principles calculations. As an illustration of this standard approach, I will describe the calculation of the phase diagrams of Gd-doped EuO and EuS using the cluster expansion technique [1]. Many problems, however, require physical insight for the selection of the relevant degrees of freedom and for an adequate representation of their interactions. The main focus of this talk will be on such problems, including the structural phase transitions at the Cr2O3 (0001) surface and the magnetic thermodynamics of the parent compounds of ferropnictide superconductors [2].

Carving Out the Space of Conformal Field Theories – David Simmons-Duffin Fri. October 28th, 2011
11:30 am-12:30 pm

Conformal Field Theories (CFTs) are theories that are symmetric under changes of distance scale, like a fractal or a Russian doll. They are basic building blocks of more general Quantum Field Theories, which can describe how nature works at its most fundamental level. Despite their importance, the range of possible behavior in CFTs is poorly understood, and often the most interesting theories resist calculation with conventional perturbative methods. However, over the last few years, new techniques have emerged for mapping out the space of these important theories. I’ll explain how to use basic mathematical consistency conditions, techniques from optimization theory (a subfield of computer science),

Photorefractive Polymers for an Updatable Holographic Display – Cory Christenson Mon. October 24th, 2011
12:30 pm-1:30 pm

Holography is a technique commonly used to display objects in three-dimensions, as it has the potential to accurately reproduce all features of the light from a real object. Holographic telepresence has been a compelling fantasy for decades, but modern science has failed to deliver such a system, primarily due to the computational power required and the lack of a suitable recording material. I will discuss my graduate work at the University of Arizona on the use of organic photorefractive polymers as a medium for updatable 3D holographic displays. These exhibit a reversible index change in response to light, and the wavelength sensitivity can be modified using different chromophores,

Energetics and Electronic Structure of Point Defects in Oxide Semiconductors: A Density Functional Approach – Fumiyasu Oba Fri. October 21st, 2011
12:30 pm-1:30 pm

Because of the crucial roles of point defects in the physical properties of pristine and doped oxide semiconductors, a fair amount of experimental research has been devoted to their characterization in previous decades. However, the understanding of the defects is limited, particularly at the atomistic and electronic level. A density functional approach is useful for the study of the defects and has provided various insights into their characteristics. In this talk, I will present our recent results on the defects in several oxide semiconductors, ZnO [1], SrTiO3 [2], BaTiO3 [3], and SnOx [4, 5], obtained using semilocal and hybrid density functional calculations.

Development of a magnetic-resonance-imaging-guided radiation-therapy device to treat cancer patients – James Dempsey Thu. October 20th, 2011
4:15 pm-5:15 pm

Nearly two-thirds of all cancer patients in the U.S. receive radiation therapy to treat their illness. Many advanced technologies have been developed to create precise and optimized ionizing radiation treatments where patients are modeled as static objects. All current radiotherapy technology, however, has a major shortcoming: it cannot determine where the radiation is actually being delivered in a patient’s body while the treatment beam is on. This is because patients aren’t static objects; they’re people, and their bodies naturally and inherently move. This movement is often significant enough to cause the radiation to miss the intended target and unnecessarily irradiate healthy tissue,

Understanding Chameleon Scalar Fields via Electrostatic Analogy – Kate Jones-Smith Tue. October 18th, 2011
11:30 am-12:30 pm

The late-time accelerated expansion of the universe could be caused by a scalar field that is screened on small scales, as in chameleon or symmetron scenarios. We present an analogy between such scalar fields and electrostatics, which allows calculation of the chameleon field profile for general extended bodies. Interestingly, the field demonstrates a `lightning rod’ effect, where it becomes enhanced near the ends of a pointed or elongated object. Drawing from this correspondence, we show that non-spherical test bodies immersed in a background field will experience a net torque caused by the scalar field. This effect, with no counterpart in the gravitational case,

Variational Studies on the Kagome Lattice – Jesse Kinder Mon. October 17th, 2011
12:30 pm-1:30 pm

The two dimensional kagome lattice is a highly frustrated spin system. When spins are placed on the vertices of the lattice with an antiferromagnetic interaction, there is no unique classical ground state. The large degeneracy of classical configurations with the same energy appear to give rise to an unusual quantum ground state. In this talk, I will discuss theoretical attempts to understand the ground state of the antiferromagnetic Heisenberg model on the kagome lattice. In the first portion of the talk, I will review several theoretical proposals for the ground state put forth over the past two decades. These fall into two basic categories: spin liquids and valence bond crystals.

Electronic liquid crystal correlations in the pseudogap phase of high Tc cuprates – Michael Lawler Thu. October 13th, 2011
4:15 pm-5:15 pm

The pseudogap phase of cuprate oxides is one of the most perplexing phases in condensed matter physics; it is a poor metal that, at lower temperatures, becomes one of the best superconductors. Recently [1], the peculiarities of the pseudogap phase were beautifully captured by STM data on Bi2Sr2CaCu2O8+x in the form of an inhomogenious spatial pattern of density of states. From these pseudogap patterns, we construct liquid crystalline order parameter fields to quantify the symmetry breaking features [2,3]. These fields reveal two properties of the pseudo gap phase.

Measuring the electronic properties of single semiconductor nanowire heterostructures using advanced optical spectroscopies – Leigh M. Smith Mon. October 10th, 2011
12:30 pm-1:30 pm

There has been intense interest in recent years to control the electronic structure in quasi one-dimensional nanowires through the fabrication of novel axial and radial heterostructures. Unlike materials in higher dimensions, nanowires have the unique ability to grow axial or radial heterostructures between almost any two materials regardless of lattice mismatch or strain. Understanding exactly how the electronic properties of the nanowire are changed through this control is extremely important and requires spectroscopies with high spatial, temporal and spectral resolution. I will discuss a number of examples in which the electronic structure in nanowire heterostructures can be modified either through strain,

Moving spins with heat: spin-Seebeck effect in a ferromagnetic semiconductor and Polarization-induced pn-junctions in wide band gap semiconductor nanowires – Roberto Myers Mon. October 3rd, 2011
12:30 pm-1:30 pm

Many proposed spin-based devices require transfer of spin into non-magnetic materials, which is usually accomplished by driving a charge current from a ferromagnet into a non-magnetic material. Heat can also be used to transfer spins into non-magnetic material using the spin-Seebeck effect, as demonstrated by Uchida et al. in permalloy[1]. We also observed this in GaMnAs [2], a ferromagnetic semiconductor. A different orientation of spin is injected into platinum bars on the hot side of the sample as compared to the cold side, and this spatial distribution of spin currents is unaffected by electrical breaks highlighting that the effect is driven by phonons in the substrate.

Temperature-accelerated dynamics and kinetic Monte Carlo simulations of thin-film growth – Jacques Amar Thu. September 29th, 2011
4:15 pm-5:15 pm

Thin-films are used in a variety of applications ranging from semiconductor technology to industrial coatings, sensors, and photovoltaic devices. In addition, understanding thin-film growth is a challenging scientific and technical problem which requires an understanding of surface and interface physics. After a brief review of some applications, I will discuss some new simulation techniques, including the kinetic Monte Carlo method as well as temperature-accelerated dynamics (TAD) and parallel TAD (parTAD) which have allowed us to make substantial progress. I will then discuss the application of these methods to study submonolayer and multilayer metal epitaxial growth. In particular, the results of simulations we have carried out in order to understand strain relaxation and “vacancy”

How Asymmetric Dark Matter May Alter the Conditions of Stardom – Andrew Zentner Tue. September 27th, 2011
11:30 am-12:30 pm

Numerous recent experimental results have reinforced interest in a class of models dubbed “Asymmetric Dark Matter” (ADM), in which the relic dark matter density results from a particle-antiparticle asymmetry. Early models of this sort were invoked to explain the fact that the cosmic baryon and dark matter densities are of the same order, yet in the standard cosmology, they are produced by distinct physical processes. In such models, the relic dark matter density results from an asymmetry (perhaps dark matter carries B-L charge), so there are no contemporary cosmic dark matter annihilations and no opportunity for indirect detection. Otherwise, these scenarios give essentially the same cosmological predictions as the standard weakly-interacting massive particle/cold dark matter paradigm,

First-principles electronic structure calculations in energy research – Emmanouil (Manos) Kioupakis Mon. September 26th, 2011
12:30 pm-1:30 pm

As the world strives to reduce its reliance on fossil fuels, materials innovations can help catalyze the switch to renewable energy and the engineering of energy-efficient devices. Powered by modern high-performance computers, s first-principles methods can provide an understanding of fundamental materials processes at the microscopic level and play an important role in the development of novel energy materials and devices. In this talk, I will present insights garnered from first-principles calculations for the study of the performance of optoelectronic devices for energy. I will discuss the loss by non-radiative recombination in nitride LED light bulbs, the internal reabsorption of light and loss in nitride green lasers and transparent conductors,

How the genome folds – Erez Lieberman Aiden Fri. September 23rd, 2011
11:30 am-12:30 pm

I describe Hi-C, a novel technology for probing the three-dimensional architecture of whole genomes by coupling proximity-based ligation with massively parallel sequencing. Working with collaborators at the Broad Institute and UMass Medical School, we used Hi-C to construct spatial proximity maps of the human genome at a resolution of 1Mb. These maps confirm the presence of chromosome territories and the spatial proximity of small, gene-rich chromosomes. We identified an additional level of genome organization that is characterized by the spatial segregation of open and closed chromatin to form two genome-wide compartments. At the megabase scale, the chromatin conformation is consistent with a fractal globule,

Culturomics: Quantitative Analysis of Culture Using Millions of Digitized Books – Erez Liebermann-Aiden Thu. September 22nd, 2011
4:15 pm-5:15 pm

We constructed a corpus of digitized texts containing about 4 per cent of all books ever printed. Analysis of this corpus enables us to investigate cultural trends quantitatively. We survey the vast terrain of ‘culturomics,’ focusing on linguistic and cultural phenomena that were reflected in the English language between 1800 and 2000. We show how this approach can provide insights about fields as diverse as lexicography, the evolution of grammar, collective memory, the adoption of technology, the pursuit of fame, censorship, and historical epidemiology. Culturomics extends the boundaries of rigorous quantitative inquiry to a wide array of new phenomena spanning the social sciences and the humanities.

Lumps and bumps in the early universe: (p)reheating and oscillons after inflation – Mustafa Amin Tue. September 20th, 2011
11:30 am-12:30 pm

Our understanding of the universe between the end of inflation and production of light elements is incomplete. How did inflation end? What did the universe look like at the end of inflation? In this talk, I will discuss the different scenarios of (p)reheating: particle production at the end of inflation. I will then concentrate on a particular scenario: the fragmentation of the inflaton into localized, long-lived excitations of the inflaton field (oscillons), which end up dominating the energy density of the universe if couplings to other fields are weak. Oscillons are produced in a large class of inflationary models which are theoretically well motivated and observationally consistent with the cosmic microwave background anisotropies.

The metal insulator transition of VO2: Shining new (synchrotron-based) light on an old problem – Louis Piper Mon. September 19th, 2011
12:30 pm-1:30 pm

The origin of the abrupt metal-insulator transition (MIT) in VO2 has been a subject of debate for several decades and remains an important problem for condensed matter physics. The change from high temperature metallic rutile phase to low temperature insulating monoclinic occurs abruptly at 360 K for bulk VO2. The origin of the MIT, whether structural (i.e. Peierls-like instability due to V-V dimerizing and tilting along the cR axis) or electronic (i.e. Mott-Hubbard transition due to strong electron correlation effects) or some combination of the two still remains a matter of debate. Recent advances in the growth of VO2 compounds have provided an opportunity to really examine this system.

Almost Quantum Mechanics – Benjamin Schumacher Thu. September 15th, 2011
4:15 pm-5:15 pm

To understand how quantum mechanics works, it is useful to imagine alternative “foil” theories that work differently. Modal quantum theory is a discrete toy model that is similar in structure to ordinary quantum theory, but based on a finite field instead of complex amplitudes. The interpretation of this theory involves only the “modal” concepts of possibility and impossibility rather than quantitative probabilities. Despite its very simple structure, our toy model nevertheless includes many of the key features of actual quantum physics: interference, complementarity, entanglement, teleportation, the impossibility of cloning, pseudo-telepathy games, nonclassical computation, and more.

Fukushima and the Future of Nuclear Energy in the U.S. – Richard Denning Thu. September 8th, 2011
4:15 pm-5:15 pm

Dr. Denning will describe what actually happened in the Fukushima accident and provide an evaluation of the failure in safety practices that led to severe fuel damage. He will also discuss the expected health, environmental, and economic consequences of the event. Risk studies indicate that a similar ”station blackout” accident could occur in the U.S. but at a very low probability. Dr. Denning will describe some differences in the capabilities of U.S. plants similar in design to the Japanese plants to mitigate the consequences of such an event. The NRC has issued their 90-day report with recommendations regarding upgrades that could be required in operating plants in the U.S.

Why are there so many interpretations of quantum mechanics? – Pierre Hohenberg Thu. September 1st, 2011
4:15 pm-5:15 pm

The foundations of quantum mechanics have been plagued by controversy throughout the 85 year history of the field. It is argued that lack of clarity in the formulation of basic philosophical questions leads to unnecessary obscurity and controversy and an attempt is made to identify the main forks in the road that separate the most important interpretations of quantum theory. The consistent histories formulation, also known as ”consistent quantum theory”, is described as one particular way (favored by the author) to answer the essential questions of interpretation. The theory is shown to be a realistic formulation of quantum mechanics, in contrast to the orthodox or Copenhagen formulation which will be referred to as an operationalist theory.

Probing crystal defects by their vibrational modes – Sukit Limpijumnong Tue. July 5th, 2011
11:00 am-12:00 pm

First principles calculations can be used to study many material properties from a fundamental point of view. This talk will cover the calculations of natural vibration frequencies (local vibrational modes) of impurities and defects in crystals. These vibration frequencies can be probed experimentally by infrared spectroscopy techniques. After a brief review of the computation techniques and details, two different cases of local vibrational modes will be explained. The first case covers the vibration frequencies of hydrogen atoms that form strong bonds with N or O in GaN and ZnO. In these cases, the vibration mode is very distinct from the crystal phonon modes.

Uniform Peak Conductivity in Single-Walled Carbon Nanotubes – Jesse Kinder Mon. June 27th, 2011
12:30 pm-1:30 pm

A carbon nanotube is a one-dimensional system in which confinement of charge carriers and an unusual band structure lead to a variety of interesting effects. Many electronic and optical properties of a nanotube depend strongly on its geometry — the way in which a two-dimensional lattice of carbon atoms is rolled up to form the nanotube. In contrast, recent Rayleigh scattering measurements by the Park group at Cornell reveal that the peak optical conductivity is approximately equal for all single-walled carbon nanotubes, independent of their geometric structure. In this talk, I will describe our efforts to understand the origin of this uniform peak conductivity.

Sign reversal in dielectric anisotropy and dielectric relaxation in bent core liquid crystals – Jagdish Vij Mon. June 13th, 2011
12:30 pm-1:30 pm

We investigate the nematic phase of a 4-cyanoresorcinol bisbenozate compound by varying its chain length from C4 to C9 using dielectric and electro-optic spectroscopy. The frequencies and dielectric strengths of the various modes are determined. The results of the sign reversal in the dielectric anisotropy are interpreted in terms of the relative dielectric strengths of the various modes, their relaxation frequencies the order parameter of the system. The results are found to be much more interesting and complex than known so far for the calamitic Mesogens-.

Experimental observation and manipulation of topological surface states – Yulin Chen Mon. May 9th, 2011
12:30 pm-1:30 pm

Three-dimensional (3D) topological insulators (TIs) are a new state of quantum matter with a bulk gap generated by the spin orbit interaction and odd number of relativistic Dirac fermions on the surface. The robust surface states of TIs can be the host for many striking quantum phenomena, such as an image magnetic monopole induced by an electric charge and Majorana fermions induced by the proximity effect from a superconductor. Recently, several classes of materials were theoretically predicted to be the simplest 3D TIs whose surface states consist of a single Dirac cone. By investigating the surface state of these materials with angle-resolved photoemission spectroscopy (ARPES),

To the GUT Scale – the Majorana Neutrino – Lindley Winslow Fri. May 6th, 2011
12:30 pm-1:30 pm

To connect our current results and those from future reactor and long baseline experiments to the preferred theory for neutrinos at the highest energy scales – a theory which explains tiny neutrino masses and enormous asymmetries of matter versus antimatter in the universe- we need one last ingredient. Neutrinos must be their own antiparticle. The third lecture will review this theory and the current generation of double beta decay experiments. The lecture will conclude with a look at a next generation detector proposal.

Download Lindley’s Slides for this talk.

“It’s Chooz Time Folks!” – Michelson Postdoctoral Prize Lecturer Lindley Winslow, Wed. May 4th, 2011
4:15 pm-5:15 pm

The last decade has seen a revolution in our understanding of the tiniest fundamental particle, the neutrino. The results of several experiments have shown that neutrinos oscillate and therefore have mass. This opens the door for neutrinos and antineutrinos to interact differently, and this little particle to explain the matter antimatter asymmetry in the universe. The first measurement to explore this possibility is a measurement of the third and smallest mixing angle governing neutrino oscillation q13. The reactor neutrino experiment Double Chooz is coming online now to make this difficult measurement. The physics of neutrino oscillation and reactor neutrino production will be reviewed.

Colloquium: It’s Chooz Time Folks! – Lindley Winslow Wed. May 4th, 2011
4:15 pm-5:15 pm

The last decade has seen a revolution in our understanding of the tiniest fundamental particle the neutrino. The results of several experiments have shown that neutrinos oscillate and therefore have mass. This opens the door for neutrinos and antineutrinos to interact differently, and this little particle to explain the matter antimatter asymmetry in the universe.

The first measurement to explore this possibility is a measurement of the third and smallest mixing angle governing neutrino oscillation θ13. The reactor neutrino experiment Double Chooz is coming online now to make this difficult measurement. The physics of neutrino oscillation and reactor neutrino production will be reviewed.

Three Neutrino Oscillation – The Missing Pieces – Lindley Winslow Tue. May 3rd, 2011
12:30 pm-1:30 pm

Out of the whirlwind of results of the last decade, a new picture is emerging. As we fit together the results, there are several missing pieces. They are the third and smallest mixing angle θ13, the neutrino mass hierarchy, and CP violation in the lepton sector. The second lecture will expand upon the derivations used in the first lecture, and present the experiments that are coming online to address these issues.

Download Lindley’s Slides for this talk

Strong-arming electron spin dynamics – Jason Petta Mon. May 2nd, 2011
12:30 pm-1:30 pm

A single electron spin in an external magnetic field forms a two-level system that can be used to create a spin qubit. However, achieving fast single spin rotations, as would be required to control a spin qubit, is a major challenge. It is difficult to drive spin rotations on timescales that are faster than the spin dephasing time and to individually address a single spin on the nanometer scale. I will describe a new method for quantum control of single spins that does not involve conventional electron spin resonance (ESR). In analogy with an optical beam splitter, we use an anti-crossing in the energy level spectrum of our quantum dot “artificial atom”

The Neutrino and Oscillation: A Revolution – Lindley Winslow Mon. May 2nd, 2011
4:15 pm-5:15 pm

In the last decade three key experiments KamLAND, SNO, and Super Kamiokande have revolutionized our understanding of the neutrino and have provided the first piece of evidence for physics beyond the standard model. This first lecture will introduce the neutrino, and derive two neutrino oscillation in vacuum and matter. The results of these key experiments will be presented and explained in the context of neutrino oscillation.

Download Lindley’s Slides for this talk.

Massive gravitons and enhanced gravitational lensing – Mark Wyman Tue. April 26th, 2011
11:30 am-12:30 pm

The mystery of dark energy suggests that there is new gravitational physics at low energies and on long length scales. On the other hand, low mass degrees of freedom in gravity are strictly limited by observations within the solar system. A compelling way to resolve this apparent contradiction is to add a galilean-invariant scalar field to gravity. Called galileons, these scalars have strong self interactions near overdensities, like the solar system, that suppress their effects on the motion of massive particles. These non-linearities are weak on cosmological scales, permitting new physics to operate. Extending galilean invariance to the coupling of galileons to stress-energy —

Scanning tunneling microscopy studies of single magnetic ions in GaAs – Jay Gupta Mon. April 25th, 2011
12:30 pm-1:30 pm

The scaling of electronic devices such as field effect transistors to nanometer dimensions requires more precise control of individual dopants in semiconductor nanostructures, as statistical fluctuations can impact device performance and functionality. Toward this end, the scanning tunneling microscope (STM) is emerging as a useful tool for its capabilities of atomic manipulation, imaging and tunneling spectroscopy. I will discuss our STM studies of Mn acceptors within the surface layer of a p-doped GaAs crystal [1]. We start by sublimating Mn adatoms onto the GaAs (110) surface, prepared by cleavage in ultrahigh vacuum. A voltage pulse applied with the STM tip allows us to replace a Ga atom in the surface with the Mn atom,

Exploring the Energy (and Lifetime) Frontiers with the CMS Experiment – Christopher Hill Thu. April 21st, 2011
4:15 pm-5:15 pm

In November 2010, the Large Hadron Collider (LHC) at CERN completed its first physics run of proton-proton collisions at sqrt(s) = 7 TeV. These data, which have been analyzed in recent months, have provided us with our first glimpse of the energy frontier. I will review why particle physicists are so excited about what we might find as we explore this newly accessible regime and present some of the scientific results which have already emerged. There are, however, a number of scenarios of physics beyond the Standard Model which predict new heavy quasi-stable particles at the LHC which could spoil the party;

Electron-electron interaction and transport in bilayer graphene – Jun Zhu Mon. April 18th, 2011
12:30 pm-1:30 pm

Bilayer graphene, or two layers of graphene stacked together in Bernal stacking, is a unique two-dimensional electron system with hyperbolic bands and a band gap tunable by the application of an electric field through the two layers. In this talk, I will describe our experiments in understanding the mechanisms of carrier transport in a gapped bilayer graphene. I will also show accurate measurements of the effective mass of bilayer graphene, from which we determine its band structure. Our results show that electron-electron interaction renormalizes the bands of bilayer and suppresses the effective mass m*. The manifestation is qualitatively different from that in conventional 2D systems.

Nano is more than size: The role of geometry in the electronic structure of carbon nanostructures – Vince Crespi Fri. April 15th, 2011
12:30 pm-1:30 pm

The atomic-scale order of highly deformable yet chemically inert carbon frameworks animates a wide range of novel structural, optical, and electronic phenomena. For example, the division of surrounding space into two disconnected zones by an impenetrable suspended graphenic sheet enables adsorption of otherwise highly co-reactive species, such as alkali and halogen, in opposite subspaces, with an intense cross-sheet charge transfer that produces a new variant of ionic binding with a uncompensated electrostatic dipoles. New physics also results when the same species is adsorbed to both sides, with unusual “which-side” symmetry breaking at certain chemical potentials. New ways to induce gaps in graphene sheets can also be designed exploiting new stacking physics.

Financial Mathematics for Physicists – Bryan Lynn Thu. April 14th, 2011
4:15 pm-5:15 pm
Learning about Aspects of Clusters and Cosmology from Weak and Strong Gravitational Lensing Approaches – Mandeep Gill Tue. April 12th, 2011
11:30 am-12:30 pm

I will cover several aspects of current astrophysics that can be probed by various regimes of lensing in simulations and data –from galaxy cluster substructure to what we can learn about cosmology from cluster weak lensing ensembles. Further, a new approach to extracting information from strongly lensed arc images that I have been involved with in recent times, and which is model-independent and has the potential to revolutionize approaches to strong lensing analyses and is very complementary to weak lensing analyses will be introduced. I will further briefly discuss initial lensing results from already-taken data of 6 clusters from the Large Binocular Telescope in Arizona,

Thick-wall tunneling in a piecewise linear and quadratic potential – Pascal Vaudrevange Tue. April 12th, 2011
11:30 am-12:30 pm

After reviewing the basics of Coleman deLuccia tunneling, especially in the thin-wall limit, I discuss an (almost) exact tunneling solution in a piecewise linear and quadratic potential. A comparison with the exact solution for a piecewise linear potential demonstrates the dependence of the tunneling rate on the exact shape of the potential. Finally, I will mention applications when determining initial conditions for inflation in the landscape. Based on arXiv:1102.4742 [hep-th].

Colloidal Quantum Dot Solar Cells – Randy Ellingson Mon. April 11th, 2011
12:30 pm-1:30 pm

Earth’s need for clean energy becomes more evident with each demonstration of the shortcomings of fossil and nuclear energy sources. All carbon-free and nuclear-free energy sources will play important roles in our energy future, but only solar energy can in principle provide all of our energy needs. I will describe current market and technology landscapes for photovoltaics, introduce the use of quantum dots (QDs) as electronic materials, and provide an overview of the developing field of colloidal QD-based thin film solar cells. Although many R&D efforts pursue the fabrication of thin film photovoltaic devices from solution-based particle and nanoparticle (QD) starting materials,

The Comprehensive Nuclear-Test Ban Treaty – Rob Nelson Thu. April 7th, 2011
4:15 pm-5:15 pm

I will review the technical history of nuclear weapons, the U.S.-Soviet nuclear arms race and efforts to control the spread of nuclear weapons after the end of the Cold War. I will then focus on technical issues related to the Comprehensive Nuclear-Test Ban Treaty, which the U.S. has signed, but not yet ratified. Finally, I will describe opportunities for students interested in careers at the intersection of science and public policy, both within the U.S. government and in non-governmental organizations.

Gravitational wave astronomy in the next decade – Xavier Siemens Tue. April 5th, 2011
11:30 am-12:30 pm

In the next decade two types of gravitational wave experiments are expected to result in the direct detection of gravitational waves: Advanced ground-based interferometric detectors and pulsar timing experiments. In my talk I will describe both types of experiments and their sensitivities to various types of gravitational wave sources. I will also discuss some of the impacts of these experiments on astronomy and cosmology.

Ab-initio Heat Transfer: Predicting thermal transport in nanostructures and materials from the atoms up – Derek Stewart Mon. April 4th, 2011
12:30 pm-1:30 pm

While electronic transport has been the focus of intensive research for nearly a century, thermal transport has proven difficult to quantify and model. However, a predictive model for thermal conductivity can improve our understanding of thermoelectric materials, thermal resistance barriers, nanoscale heat transport, and even geologic heat transfer. In this talk, I will discuss the development of a new first principles framework to model thermal transport in materials and nanostructures. Using density functional perturbation theory, we are able to calculate both harmonic and anharmonic interatomic force constants. Coupling these terms with a Boltzmann transport approach, we are able to demonstrate excellent agreement between the calculated and measured lattice thermal conductivities of technologically relevant semiconductors (silicon,

Black Holes and Thermodynamics – Jennie Traschen Thu. March 31st, 2011
4:15 pm-5:15 pm

In 1971 Hawking published the Area Theorem, which shows that the area of a black hole either increases or stays the same. Two years later, Bardeen, Carter, and Hawking proved a theorem which relates the changes in the mass of a black hole, to changes in its area. These two results had a striking formal resemblance to the second and first laws of classical thermodynamics respectively. However, since nothing comes out of a black hole, it seemed that a black hole can not radiate and can not have a temperature, and so can not really be a thermodynamic system. Then in 1975,

Testing Dark Energy with Massive Galaxy Clusters – Michael Mortonson Tue. March 29th, 2011
11:30 am-12:30 pm

Existing observations of the cosmic expansion history place strong restrictions on the rate of large scale structure growth predicted by various dark energy models. In the simplest Lambda CDM scenario, current observations enable percent-level predictions of growth, which can be interpreted in terms of the expected abundance of massive galaxy clusters at high redshift. I will show that these predictions from current data set a firm upper limit on the cluster abundance in the more general class of quintessence models where dark energy is a canonical, minimally-coupled scalar field. While the most massive clusters known today appear to lie just below this limit,

Toward Graphene-Based Photovoltaics – Liang-shi Li Mon. March 28th, 2011
12:30 pm-1:30 pm

Solution-processable thin-film solar cells can be competitive with silicon-based ones in terms of electricity output/cost ratio and therefore have great potential in solar energy utilization. Due to the requirement for efficient light harvesting, however, so far the most successful low-cost thin-film solar cells require materials containing either rare or toxic metals. In my talk I will discuss our efforts in making graphene, which is primarily made of carbon, an active component for solar energy conversion. Our work is based on the synthesis of solution-processable colloidal graphene quantum dots with tunable size and bandgap. Our spectroscopic studies have shown that the graphene quantum dots have some unique electro-optical properties,

New observational power from halo bias – Sarah Shandera Tue. March 22nd, 2011
11:30 am-12:30 pm

Non-Gaussianity of the local type will be particularly well constrained by large scale structure through measurements of the power spectra of collapsed objects. Motivated by properties of early universe scenarios that produce observationally large local non-Gaussianity, we suggest a generalized local ansatz and perform N-body simulations to determine the signatures in the bias of dark matter halos. The ansatz introduces two bispectral indices that characterize how the local non-Gaussianity changes with scale and these generate two new signals in the bias. While analytic predictions agree qualitatively with the simulations, we find numerically a stronger observational signal than expected, which suggests that a better analytic understanding is needed to fully explain the consequences of primordial non-Gaussianity.

Dark Energy: constant or time variable? (… and other open questions) – Bharat Ratra Thu. March 17th, 2011
4:15 pm-5:15 pm

Experiments and observations over the last decade have persuaded cosmologists that (as yet undetected) dark energy is by far the main component of the energy budget of the universe. I review a few simple dark energy models and compare their predictions to observational data, to derive dark energy model-parameter constraints and to test consistency of different data sets. I conclude with a list of open cosmological questions.

Constraining the cosmic growth history with large scale structure – Rachel Bean Tue. March 15th, 2011
11:30 am-12:30 pm

We consider how upcoming, prospective large scale structure surveys, measuring galaxy weak lensing, position and peculiar velocity correlations, in tandem with the CMB temperature anisotropies, will constrain dark energy when both the expansion history and growth of structure can be modified, as might arise if cosmic acceleration is due to modifications to GR. We consider an equation of state figure of merit parameter, and analogous figure of merit parameters for modified gravity, to quantify the relative constraints from CMB, galaxy position, lensing, and peculiar velocity observations and their cross correlations, independently and in tandem.

The 2010 Nobel (Sciences) Prize-fest – Tim Atherton, Yanming Wang, and Paul Tesar Thu. March 3rd, 2011
4:15 pm-5:15 pm

Three 15-minute talks on the 2010 Nobel prizewinners and their work

The New World of Gamma Ray Astronomy – Lucy Fortson Thu. February 24th, 2011
4:15 pm-5:15 pm

With the third generation ground-based gamma-ray telescopes delivering over a hundred new TeV emitting objects and with the new Fermi satellite providing greatly improved sensitivity in the GeV energy regime, gamma ray astronomy is entering a golden age. I will first review the basics of ground-based gamma-ray astronomy and the Air Cherenkov Telescope method of detection. I will then describe VERITAS – an array of four gamma ray telescopes located at Mt. Hopkins, Arizona – and some of the recent results from the first few years of the VERITAS observing program, paying attention to the observations of several new TeV emitting active galactic nuclei and the discovery of the starburst galaxy M82 in TeV gamma rays.

From Lasing in Soft-Composite Materials to Optical Transparency in Metamaterials – Giuseppe Strangi Mon. February 21st, 2011
4:15 pm-5:15 pm

Lasing materials range from periodic systems such as photonic crystals to partially ordered and disordered dielectric materials that scatter light diffusively. Soft materials, in particular liquid crystals, may be manipulated easily and have interesting optical properties. They are extremely promising for engineering photonic nano- structures, either as stand-alone devices or as part of innovative integrated systems. These applications can range from photonics to the bio-medical arena where miniaturized tunable laser sources may find a vast area of uses, such as optical tweezers, endoscopic sources for cancerous tissues treatment, lab-on-chip and other still yet-to- be-conceived purposes. Here, the investigation of ordered and disordered soft nano-structures to achieve compact,

What to do with 350,000 astronomers – Chris Lintott Fri. February 18th, 2011
11:30 am-12:30 pm

Since its launch in 2007, the Galaxy Zoo project has involved hundreds of thousands of volunteers in the morphological classification of galaxies. Project PI Chris Lintott will review the results – which include a new understanding of the importance of red spirals – and their implications for our understanding of galaxy formation. The project has now expanded to include tasks ranging from discovering planets through to lunar classification, and the talk will also discuss the potential of this ‘citizen science’ method to help scientists cope with massive modern data sets.

The Persistent Mystery of the Highest Energy Cosmic Ray – Corbin Covault Thu. February 17th, 2011
4:15 pm-5:15 pm

One of the longest-standing mysteries of fundamental astrophysics is the origin and nature of the highest energy cosmic rays. These particles are the most energetic in the universe, arriving to the Earth from all directions in outer space. When these particles strike the earth’s atmosphere, they produce extensive air showers made of billions of secondary particles. The Pierre Auger Observatory has been designed and built to directly confront this mystery by making extensive measurements of air showers from these cosmic rays. After several years of operation, results from Auger have revealed key properties of the cosmic rays in terms of their energies,

Two packing problems – Narayanan Menon Thu. February 10th, 2011
4:15 pm-5:15 pm

I will discuss progress in two ongoing sets of experiments on the packing of macroscopic objects. The first of these is a neglected aspect of the old problem of packing identical spheres. Much attention has recently been paid to packings of frictionless spheres, particularly to the geometry and mechanics of the random close packed state. I will report new results on the opposite limit: that of the loosest mechanically stable packings achievable in systems of frictional spheres. The second class of packing problems I will discuss is the packing of a thin sheet in a volume of much smaller linear dimension.

Astrophysics with Gravitational-Wave Detectors – Vuk Mandic Tue. February 8th, 2011
11:30 am-12:30 pm

Gravitational waves are predicted by the general theory of relativity to be produced by accelerating mass systems with quadrupole moment. The amplitude of gravitational waves is expected to be very small, so the best chance of their direct detection lies with some of the most energetic events in the universe, such as mergers of two neutron stars or black holes, Supernova explosions, or the Big-Bang itself. I will review the status of current gravitational-wave detectors, such as the Laser Interferometer Gravitational-wave Observatory (LIGO), as well as some of the most recent results obtained using LIGO data. I will also discuss plans and expectations for the future generations of gravitational-wave detectors.

InN and ZnO: Unexpected Commonalities – Steven Durbin Mon. February 7th, 2011
12:30 pm-1:30 pm

InN is an infrared bandgap semiconductor (although it hasn’t always been that way); ZnO is an ultraviolet bandgap material used in applications from gas sensors to breakfast cereals. Surprisingly, these ostensibly disparate materials are more closely related than we might think: for both, p-type doping is problematic, the surface exhibits significant electron accumulation, and undoped samples are characterized by a large background electron concentration. In this talk I will describe some of our work to date geared towards developing a better understanding of these and closely related materials, which have significant device potential for a large variety of applications.

Pi-conjugated organic materials: properties, applications and the importance of interfaces – Mats Fahlman Thu. February 3rd, 2011
4:15 pm-5:15 pm

Electronics applications such as light emitting devices for lighting and flat panel displays, transistors, solar cells and sensors based on p-conjugated organic materials are presently being developed and have in some cases reached the market. Here is given an overview of the materials properties of p-conjugated molecules, in particular how optical absorption and luminescence as well as the electron- and hole-injection levels can be tailored through organic synthesis. We briefly discuss the strengths and weaknesses of organic electronic and spintronic applications where p-conjugated materials currently are used. The importance of interfaces in organic electronic applications is highlighted as e.g. solar cells,

New and Old Massive Gravity – Claudia de Rham Tue. February 1st, 2011
11:30 am-12:30 pm

TBA

Accurate and efficient solutions of wave propagation problems in periodic media – Catalin Turc Mon. January 31st, 2011
12:30 pm-1:30 pm

Many devices designed to guide and control waves rely on periodic structures on the wavelength scale: these include diffraction gratings (used to squeeze multiple signals onto a single optical fiber, and in our highest-powered lasers), photonic crystals (the most promising route to energy-efficient ultra-fast optical computation on a chip), meta-materials (allowing the control of waves in ways impossible in naturally-occurring media), and solar cells. I will present a class of efficient and accurate numerical methods based on boundary integral equations for the solution of wave propagation problems in piece-wise homogeneous periodic media. The main ideas behind these algorithms are (1) a novel representation of quasi-periodic Green’s functions that converges fast and (2) acceleration techniques based on equivalent sources and FFTs.

A Biophysical Perspective of Understanding Nanoparticles at Large – Pu-Chun Ke Thu. January 27th, 2011
4:15 pm-5:15 pm

In this talk I will present a biophysical perspective that describes the fate of nanoparticles in both the aqueous phase and in living systems. Specifically, I will show the correlations between the physicochemistry of fullerenes and their uptake, translocation, transformation, transport, and biodistribution in mammalian and plant systems, at the molecular, cellular, and whole organism level. In addition to fullerenes and their structural derivatives, I will describe the biological and environmental implications and applications of the condensed matter of carbon nanotubes and the soft matter of dendritic polymers. The main purpose of this talk is to demonstrate the vast opportunities and unique advantages of applying experimental and simulation biophysics and nanoscience to the research field of understanding nanoparticles at large.

Advanced Materials Stabilized by Interfacial Particles – Paul S. Clegg Thu. January 20th, 2011
4:15 pm-5:15 pm

Emulsions, typically droplets of oil in water, are widely used in, e.g. cosmetics, paints, foods and polymer synthesis. The surface of the droplet, where the two liquids meet, is energetically expensive; to make the droplets long lived this energy cost is often reduced by adding a molecular surfactant. The focus of my research is the new physics which emerges when the molecular surfactant is replaced by colloidal particles. Because the particles are mesoscale objects they are extremely strongly trapped at the droplet interface and they also modify the average properties of the individual droplets. I will demonstrate how these characteristics lead to novel composite materials.

A new method for cosmological parameter estimation from Supernovae Type Ia data – Marisa March Tue. January 18th, 2011
11:30 am-12:30 pm

We present a new methodology to extract constraints on cosmological parameters from SNIa data obtained with the SALT lightcurve fitter. The power of our Bayesian method lies in its full exploitation of relevant prior information, which is ignored by the usual chisquare approach. Using realistic simulated data sets we demonstrate that our method outperforms the usual chisquare approach 2/3 of the times. A further benefit of our methodology is its ability to produce a posterior probability distribution for the intrinsic dispersion of SNe. This feature can also be used to detect hidden systematics in the data.

Aggregating Dyes and Chromonic Liquid Crystals – Peter Collings Thu. January 13th, 2011
4:15 pm-5:15 pm

Chromonic liquid crystals form when molecules aggregate into anisotropic shapes at high enough density to promote orientational order. There is strong evidence that in some systems the aggregates are simple columnar stacks of molecules and that the aggregation process is governed by free energy changes that are independent of the size of the aggregate. Theoretically such systems should not possess a critical concentration or critical temperature for aggregation, and this is confirmed by experimental results. However, there is also excellent evidence that in one system a critical concentration or critical temperature for aggregation occurs. There is also good evidence that the aggregate structure can differ from a simple stack of molecules in several ways.

Smart Polymeric Materials: From Fundamental Science to New Technologies – Mark G. Kuzyk Wed. January 12th, 2011
4:15 pm-5:15 pm

Dye doped polymers, which were originally designed for nonlinear-optical applications, combine the good optical quality and processabilty of the host polymer with the optical and electrical properties of the dopant. Combining the nonlinear-optical and photomechanical properties in a single material may lead to utrasmart morphing materials with emergent properties. In this talk, I will discus our research on the mechanisms of of the photomechanical effect in dye-doped liquid crystal elastomers, demonstration of novel devices, and the observation of new phenomena such as self-healing following photodegradation. To conclude, I will speculate on futureque applications of highly integrated utra-smart photomechanical materials.

K-essence Interactions with Neutrinos: Flavor Oscillations without Mass – Christopher Gauthier Tue. December 7th, 2010
11:30 am-12:30 pm

In this talk we discuss a novel means of coupling neutrinos to a Lorentz violating background k-essence field. K-essence is a model of dark energy, which uses a non-canonical scalar field to drive the late time accelerated expansion of the universe. We propose that neutrinos couple to the k-essence induced metric rather than the space-time metric. The immediate effect that this has will be to modify the energy-momentum relation of the neutrino. This implies that the neutrino velocity will in general be different from the speed of light, even if the neutrino is massless. Later we will see that k-essence can also induce neutrino oscillations even without a neutrino mass term.

Ferromagnetic semiconductors and the role of disorder – Bruce Wessels Mon. December 6th, 2010
12:30 pm-1:30 pm

Magnetic semiconductors having Curie temperature greater than 300 K are of interest for a wide variety of spintronic device applications. Short-range order has been reported to stabilize ferromagnetism in transition metal-doped III-V compound semiconductors. While both theory and experiment have centered on dilute magnetic semiconductors where the magnetic ions substitute randomly for cation sites, there is increasing evidence that correlated substitution needs to be considered. Evidence of correlated substitution comes from structural analysis (extended x-ray absorption fine structure (EXAFS)), magnetic property and recent magneto-optical property measurements as well as theory. Furthermore, there is growing theoretical and experimental support that ferromagnetic semiconductors with Curie temperatures well above room temperature can be formed through correlated substitution.

Cosmology with the South Pole Telescope – John Ruhl Thu. December 2nd, 2010
4:15 pm-5:15 pm

The South Pole Telescope is dedicated to mapping several thousand square degrees of the southern sky at millimeter wavelengths. Four years into the survey, we are using the data to better understand the formation of large scale structure in the universe, and to constrain the character of the elusive Dark Energy which dominates the energy density of the universe but is (so far) not at all understood. In this talk I will describe the SPT and our recent findings, and discuss how upcoming results and future work will shed further light on the nature of things Dark.

Chemical Design of Magnetic Nanomaterials – Ana Cristina Samia Mon. November 29th, 2010
12:30 pm-1:30 pm

Nanosized magnetic materials continue to attract great interest due to their wide range of potential applications from data storage to medical diagnostics and therapy. Each application demands unique magnetic characteristics of the nanoparticles. Hence, the ability to tailor their properties is of considerable importance. A first step towards understanding the correlation between magnetic properties and nanostructure is the development of robust synthetic approaches to prepare magnetic materials with controllable nanoarchitectures. In this presentation the synthesis of metal and metal oxide magnetic nanoparticles using wet chemical approaches is presented. By carefully tuning the synthesis conditions, different sizes, shapes and compositions can be prepared.

Imaging 3D spatiotemporal hemodynamics of single cortical vessels in vivo using two-photon laser scanning microscopy – Peifang Tian Mon. November 22nd, 2010
12:30 pm-1:30 pm

The dynamics response of individual cerebral vessels to sensory-stimuli is crucial to form a mechanistic understanding of functional imaging technologies, such as functional MRI (fMRI), as well as for understanding neurovascular dysfunction, as occurs in stroke and dementia. Using optical imaging technologies such as two-photon laser scanning microscopy and the rat primary sensory cortex as our animal model, we have characterized the stimulus-evoked cerebral hemodynamic response on the level of single arterioles and capillaries throughout a significant three-dimensional volume (~1-2mm3) in vivo. Further, we will relate this characterization to the underlying neuronal electrical activity and the angioarchitecture. In this talk,

Electroweak stars: Electroweak Matter Destruction as an Exotic Stellar Engine – Dejan Stokovic Thu. November 18th, 2010
4:15 pm-5:15 pm

Stellar evolution from a protostar to neutron star is of one of the best studied subjects in modern astrophysics. Yet, it appears that there is still a lot to learn about the extreme conditions where the fundamental particle physics meets strong gravity regime. After all of the thermonuclear fuel is spent, and after the supernova explosion, but before the remaining mass crosses its own Schwarzschild radius, the temperature of the central core of the star might become higher than the electroweak symmetry restoration temperature. The source of energy, which can at least temporarily balance gravity, are baryon number violating instanton processes which are basically unsuppressed at temperatures above the electroweak scale.

Light from Cosmic Strings – Tanmay Vachaspati Tue. November 16th, 2010
11:30 am-12:30 pm

TBA

Stories of Large Scale Graphene – Yong Chen Mon. November 15th, 2010
12:30 pm-1:30 pm

Graphene has rapidly risen in the past few years to become one of the most actively researched topics in condensed matter physics and nanoscience due to its numerous remarkable properties and potential applications. Perhaps the best known method to make graphene has been the “scotch tape” technique (to exfoliate graphite), used just a few years ago by graphene pioneers Geim and Novoselov (who were awarded the physics Nobel in 2010) to unlock the novel physics of graphene. This simple method, however, produces only very small graphene flakes (typically tens of microns) and therefore is not sufficient for large scale production of graphene to fully realize its potentials.

Rethinking MR: Collecting information instead of images – Mark Griswold Thu. November 11th, 2010
4:15 pm-5:15 pm

Magnetic resonance imaging (MRI) provides exquisite depiction of anatomy and function without the ionizing radiation found in e.g. CT or PET. However, significant drawbacks still exist. This is primarily due to the limited speed and signal-to-noise ratio (SNR) of MRI, and most important, the fact that these two quantities are linked to each other. Conventionally, as with any linear system, any increase in imaging speed has required a loss in SNR and vice versa. In order to realize any truly dramatic increases in either SNR or imaging time, some way to break this relationship must be found. New developments in the world of information theory,

Modeling defects, microstructure, and shape evolution in orientationally ordered soft materials: nematic elastomers and lipid vesicles – Robin Selinger Mon. November 8th, 2010
12:30 pm-1:30 pm

Liquid crystal elastomers, sometimes called “artificial muscles,” combine the elastic properties of rubber with the molecular order properties of liquid crystals. These fascinating materials stretch, shrink, bend or flap in response to changes in temperature, illumination, or applied fields, due to strong coupling between orientational order and elastic strain. Their mechanical response under applied strain is also peculiar, showing in some geometries a pronounced plateau in the stress-strain curve, accompanied by formation of a striped microstructure with director rotation in alternating directions. We construct a mesoscale model of this system based on a simple free energy functional and implement it using finite element elastodynamics.

The quest for dilute ferromagnetism in semiconductors: Guides and misguides by theory – Stephan Lany Thu. November 4th, 2010
4:15 pm-5:15 pm

Semiconductivity (SC) and ferromagnetism (FM) are an unlikely couple, each having quite different desires in regard of the electronic band structure (High density of states at the Fermi level for FM, but low or moderate for SC). In the search for materials that make this difficult relationship work, electronic structure theory has played a prominent role, predicting new diluted magnetic semiconductor (DMS) materials, offering explanations and suggesting models for the underlying physical mechanisms. However, treacherous pitfalls need to be avoided along the path leading from a density functional calculation to a realistic model for DMS. In this talk, I will highlight examples how such calculations can produce “false positives”,

Testing the No-Hair Theorem with Astrophysical Black Holes – Dmitrios Psaltis Tue. November 2nd, 2010
11:30 am-12:30 pm

The Kerr spacetime of spinning black holes is one of the most intriguing predictions of Einstein’s theory of general relativity. The special role this spacetime plays in the theory of gravity is encapsulated in the no-hair theorem, which states that the Kerr metric is the only realistic black-hole solution of the vacuum field equations. Recent and anticipated advances in the observations of black holes throughout the electromagnetic spectrum have secured our understanding of their basic properties while opening up new opportunities for devising tests of the Kerr metric. In this talk, I will show how imaging and spectroscopic observations of accreting black-holes with current and future instruments can lead to the first direct test of the no-hair theorem with an astrophysical object.

Cosmological Constraints from Peculiar Velocities – Arthur Kosowski Fri. October 29th, 2010
11:30 am-12:30 pm

Peculiar velocities of galaxies and clusters are induced during the formation of structure in the universe via gravitational forces. As such, they provide a potentially powerful route to constraining both the growth of structure and the expansion history of the universe. Traditional methods of velocity determination have not yet been able to measure velocities at cosmological distances with sufficient accuracy to allow cosmological constraints. I will discuss two possible methods of measuring peculiar velocities: directly via the kinematic Sunyaev-Zeldovich effect for galaxy clusters, and using distance measurements of type-Ia supernovae in future large surveys. I will discuss measurement prospects, and show that upcoming probes of mean pairwise velocity will have the potential to plac significant constraints on both dark energy and modifications of gravity while limiting systematic errors

Heterovalent ternary compounds, a new form of semiconductor property engineering: from electronic energy bands to lattice dynamics – Walter Lambrecht Thu. October 28th, 2010
4:15 pm-5:15 pm

Over the last five years or so, my group has studied the properties of a new family of nitride semiconductors, the II-IV-N2, the compounds, such as ZnGeN2, ZnSiN2. One can view this as a new way to modify the properties of GaN semiconductors. Instead of isovalent substitution of different group III elements, we substitute alternately a group II and IV element, coordinating each N tetrahedrally with two of each. Unlike isovalent substitution, which leads to disordered alloys, this type of substitution leads to well ordered compounds. Another example,

Polymeric materials for printable electronic applications: from synthesis to device characterization – Genevieve Sauve Mon. October 25th, 2010
12:30 pm-1:30 pm

Conjugated polymers are considered by many as leading candidates to produce the next generation of electronics. This belief is based upon several factors: (a) they can be solution-processed using established printing technologies to give flexible, lightweight functional thin films, allowing for low-cost and large-scale production. (b) Several already have desirable properties for practical applications. In the first part of this talk, I will discuss strategies to optimize transistors and show results for well-defined poly(3-alkylthiophene)s and block copolymers of poly(3-hexylthiophene). In the second part of the talk, I will talk about my research here at CWRU on polymer-based photovoltaics.

Strands of Superconductivity at the Nanoscale – Paul Goldbart Thu. October 21st, 2010
4:15 pm-5:15 pm

Superconducting circuitry can now be fabricated at the nanoscale, e.g., by depositing suitable materials on to single molecules, such as DNA or carbon nanotubes. I shall discuss various themes that arise when superconductivity is explored in this new regime, including the thermal passage over and quantum tunneling through barriers by the superconducting condensate as a whole, as well as a strange, hormetic effect that magnetism can have on nanoscale superconductors. I shall describe nanoscale superconducting quantum interference devices, which are subtly sensitivity to magnetic fields and patterns of supercurrent — features that hint at uses of superconducting nanocircuitry, e.g., in mapping quantum phase fields and testing for superconducting correlations in novel materials.

Absorption/Expulsion of Oligomers and Linear Macromolecules in a Polymer Brush – Sergei Egorov Mon. October 18th, 2010
12:30 pm-1:30 pm

The absorption of free linear chains in a polymer brush was studied with respect to chain size and compatibility with the brush by means of Monte Carlo simulations and Density Functional Theory / Self-Consistent Field Theory at both moderate and high grafting densities using a bead-spring model. Different concentrations of the free chains were examined. When free chains are incompatible with the brush, all oligomeric species are almost completely ejected by the polymer brush irrespective of their length. For compatible case, we find that in going from shorter to longer chains, the absorbed amount undergoes a sharp crossover from weak to strong absorption.

IR issues in Inflation – Richard Holman Fri. October 15th, 2010
11:30 am-12:30 pm

I review some problems involving IR divergences in de Sitter space that give rise to behavior such as secular growth of fluctuations and discuss the use of the Dynamical Renormalization Group as a tool to resum and reinterpret these divergences. Time permitting, I’ll also discuss some more recent work on the breakdown of the semiclassical approximation in de Sitter space.

From quantum mechanics to radiology to business, starting with the basic physics of vascular imaging – Mark Haacke Thu. October 14th, 2010
4:15 pm-5:15 pm

TBA

The Angular Distribution of the Highest-Energy Cosmic Rays – Andrew Jaffe Tue. October 12th, 2010
11:30 am-12:30 pm

TBA

Fractionalization in Mesoscopic Rings – Smitha Vishveshwara Mon. October 11th, 2010
12:30 pm-1:30 pm

A spectacular phenomenon that can occur in strongly correlated low dimensional systems is that of fractionalization. In such electronic systems, quasiparticles excitations can carry a fraction of the electron’s charge and can have anyonic quantum statistics which is neither fermionic nor bosonic. Here, mesoscopic ring geometries are introduced as a means of bringing out novel signatures of both charge fractionalization and non-Abelian anyonic statistics. It is shown that power maps of quasiparticle motion around a thin ring can act as measures of fractionalization complementary to recent cutting-edge studies in etched quantum wires. A proposal is presented for probing the non-Abelian statistics of recent tour de force realizations of fractional vortices in superconducting mesoscopic rings.

Bulk viscosity and the damping of neutron star oscillations – Mark Alford Fri. October 8th, 2010
11:30 am-12:30 pm

How do we learn about the phases of matter beyond nuclear density? They are to be found only in the interior of neutron stars, which are inaccessible and hard to observe. One approach is through the oscillations of neutron stars, which depend on the viscosity of their interior. If the viscosity is low enough then “r-mode” oscillations arise spontaneously and cause the star to spin down. Finding fast-spinning stars therefore puts limits on the viscosity viscosity and hence on the possible phases present in the interior of the star. This talk discusses non-linear effects which arise for large amplitude “suprathermal”

Exciton-Plasmon Interactions and Fano Resonances in Nanostructures – Alexander Govorov Mon. October 4th, 2010
12:30 pm-1:30 pm

Coulomb and electromagnetic interactions between excitons and plasmons in nanocrystals cause several interesting effects: energy transfer between nanoparticles (NPs), plasmon enhancement, reduced exciton diffusion in nanowires (NWs), exciton energy shifts, Fano interference effect, and non-linear phenomena [1-3]. Using transport equations for excitons, we model exciton transfer in NWs and explain the origin of the blue shift of exciton emission observed during recent experiments with hybrid NW-NP assemblies [2]. We also look at optical responses of artificial light-harvesting complexes composed of chlorophylls, bacterial reaction centers, and NPs [3]. We show that, using superior optical properties of metal and semiconductor NPs, it is possible to strongly enhance the efficiency of light harvesting in such complexes [3].

Morphology and dynamics of polymers at interfaces – Mesfin Tsige Thu. September 30th, 2010
4:15 pm-5:15 pm

The surface and interfacial properties of polymers play a key role in many technological applications ranging from telecommunication to biotechnology. Most of the intended applications strongly depend on wetting and adhesion phenomena. Understanding the structure and thermodynamic properties of polymers at interfaces is thus an area of fundamental and current technological interest. Although excellent experimental progress has been made over the years in understanding the molecular structure of polymers in contact with various environments, the quantitative analysis has been more difficult. In the past few years, computer simulations have made significant contributions by providing the details that are lacking in the experimental data.

CMB in a Box – Raul Abramo Tue. September 28th, 2010
11:30 am-12:30 pm

First, I will show that the line-of-sight solution to cosmic microwave anisotropies in Fourier space, even though formally defined for arbitrarily large wavelengths, leads to position-space solutions which only depend on the sources of anisotropies inside the past light-cone of the observer. This happens order by order in a series expansion in powers of the visibility function. Second, I will show that the Fourier-Bessel expansion of the physical fields (including the temperature and polarization momenta) is superior to the usual Fourier basis as a framework to compute the anisotropies. In that expansion, for each multipole $l$ there is a discrete tower of momenta $k_{i,l}$ (not a continuum) which can affect physical observables,

Embedded nanopillars for solar cell applications – Jingbiao Cui Mon. September 27th, 2010
12:30 pm-1:30 pm

Nanopillar radial junctions achieved by embedding nanopillars in absorbing thin films have potential for improved performance in solar cells due to increased junction area and improved charge carrier collection. This type of structure is still in its initial stage of development by using expensive and complicated microfabrication processes. An economic approach to the fabrication of nanopillar p-n junction solar cells has been investigated recently using a simple two-step electrodeposition method. The nanopillar heterojunctions are composed of n-type ZnO nanopillar arrays embedded in p-type Cu2O thin films, showing improved performance as compared with the planar thin film structures. While much effort is needed to optimize the device overall performance,

High-efficiency thermoelectric materials: new design strategies, new applications – Joseph Heremans Thu. September 23rd, 2010
4:15 pm-5:15 pm

Thermoelectric energy converters are solid state devices that convert thermal to electrical energy, and are used in heat pumps and power generators. They have no moving parts, conveying them the inherent advantages of compactness and robustness that have traditionally been offset by their low efficiency. This changed in the last decade when several classes of materials were developed with double the efficiency of commercial materials. Consequently, the new materials are poised to play a significant role in energy recovery applications from waste heat, and in new efficient air-conditioning schemes.

This talk will briefly review the new applications, as well as the recent materials design strategies used.

Does Quantum Mechanics Imply Gravity? – Harsh Mathur Tue. September 21st, 2010
11:30 am-12:30 pm

TBA

Studies of reflection-band defects in 1D polymeric photonic crystals – Guilin Mao Mon. September 20th, 2010
12:30 pm-1:30 pm

Disorder or variation of the periodic structure of 1D-photonic crystal can lead to defects in the reflection band, characterized by one or more spectrally narrow transmission peaks inside that band. At or near such defects, changes in the effective group velocity of the light result in interesting optical phenomena such as Faraday rotation enhancement and gain enhancement in a distributed feedback (DFB) photonic crystal laser. In this talk, we present experimental results on and a theoretical interpretation of magneto-optic rotation and DFB lasing within the reflection band of CLiPS polymer multilayers.

Triboelectric Charging in Granular Systems – Daniel Lacks Mon. September 13th, 2010
12:30 pm-1:30 pm

Have you ever received a shock when you touched a doorknob after shuffling across a carpeted floor? The culprit, known as triboelectric charging, is also responsible for phenomena as innocuous as a rubbed balloon that makes your hair stand on end, or as dramatic as a lightning strike. While it is familiar to every child, fundamental understanding of triboelectric charging is so poor that even the most basic questions are still being debated, such as whether the transferred charge species are electrons or ions. Scientific progress is difficult because triboelectric charging is a non-equilibrium process (separated surfaces are neutral at equilibrium) that involves changes in electron states and occurs at a level of one electron per 100,000 surface atoms (physical and/or chemical defects at this low level likely control the behavior).

Spin torque effects in magnetic tunnel junctions – Olle Heinonen Thu. September 9th, 2010
4:15 pm-5:15 pm

The prediction by Slonczewski and Berger that currents in magnetic heterostructures can exert a torque on the magnetization in the structures has lead to intense research over the past decade. This is both because of a new area of fundamental physics made possible by coupling DC currents and spin dynamics, as well as technological applications, such as magnetic random access memories and nano-scale high-frequency oscillators, in spintronics. Magnetic tunnel junctions (MTJs) consist of two magnetic layers separated by an insulator. In such structures, spin torque can induce a range of magnetization dynamics from coherent oscillations to switching and chaotic motion.

Galileon Inflation and Non-Gaussianities – Andrew Tolley Tue. September 7th, 2010
11:30 am-12:30 pm

I will discuss a new class of inflationary models based upon the idea of Galileon fields, scalar fields that exhibit non-linearly realized symmetries. These models predict distinctive non-Gaussian features in the primordial power spectrum, and I will discuss how they relate with, and can be distinguished from, canonical inflation, k-inflation, ghost inflation, and DBI-inflationary models.

Massively parallel Density functional calculations for thousands of atoms: KKRnano – Alexander Thiess Mon. August 30th, 2010
12:30 pm-1:30 pm

Existing highly precise density functional method for electronic structure calculations are mostly restricted to the treatment of at maximum a few hundred inequivalent atoms. This limitation leaves many open questions in material science e.g. on complex defects and defect-defect interaction unresolved. KKRnano is a new massively parallel DFT-algorithm in the framework of the KKR Green function method which we developed and optimized for large-scaled applications of thousands of atoms. In order to deal with the enormous computational requirements of such calculations we have implemented four levels of parallelization, which allows for an efficient use of hundreds of thousands of processors on the latest generation of supercomputers as Blue Gene.

Michelson Lectures — High-Energy Physics with Low-Energy Symmetry Studies – David Hanneke Fri. May 14th, 2010
11:30 am-12:30 pm

Discrete symmetries — charge conjugation (C), parity inversion (P), time reversal (T), and their combinations — provide insight into the structure of our physical theories. Many extensions to the Standard Model predict symmetry violations beyond those already known. From the first evidence of P-violation in the 1950s using cold atoms, low-energy, high-precision experiments have quantified existing violations and constrained further ones. In this lecture, I will describe several searches for discrete symmetry violations with low-energy experiments. T-violation, closely related to matter/antimatter asymmetry through the CPT theorem, is tightly constrained by searches for intrinsic electric dipole moments. CPT-violation — the only combination of these symmetries obeyed by the entire Standard Model —

High-Energy Physics with Low-Energy Symmetry Studies – David Hanneke Fri. May 14th, 2010
12:30 pm-1:30 pm

Discrete symmetries — charge conjugation (C), parity inversion (P), time reversal (T), and their combinations — provide insight into the structure of our physical theories. Many extensions to the Standard Model predict symmetry violations beyond those already known. From the first evidence of P-violation in the 1950s using cold atoms, low-energy, high-precision experiments have quantified existing violations and constrained further ones. In this lecture, I will describe several searches for discrete symmetry violations with low-energy experiments. T-violation, closely related to matter/antimatter asymmetry through the CPT theorem, is tightly constrained by searches for intrinsic electric dipole moments. CPT-violation — the only combination of these symmetries obeyed by the entire Standard Model —

Michelson Lectures — Cavity Control in a Single-Electron Quantum Cyclotron: An Improved Measurement of the Electron Magnetic Moment – David Hanneke Thu. May 13th, 2010
11:30 am-12:30 pm

Measurements of the electron magnetic moment (the “g-value”) probe the electron’s interaction with the fluctuating vacuum. With a quantum electrodynamics calculation, they provide the most accurate determination of the fine structure constant. Comparisons with independent determinations of the fine structure constant are the most precise tests of quantum electrodynamics and probe extensions to the Standard Model of particle physics. I will present two new measurements of the electron magnetic moment. The second, at a relative uncertainty of 0.28 parts-per-trillion, yields a value of the fine structure constant with a relative accuracy of 0.37 parts-per-billion, over 10-times smaller uncertainty than the next-best methods.

Cavity Control in a Single-Electron Quantum Cyclotron: An Improved Measurement of the Electron Magnetic Moment – David Hanneke Thu. May 13th, 2010
4:15 pm-5:15 pm

Measurements of the electron magnetic moment (the “g-value”) probe the electron’s interaction with the fluctuating vacuum. With a quantum electrodynamics calculation, they provide the most accurate determination of the fine structure constant. Comparisons with independent determinations of the fine structure constant are the most precise tests of quantum electrodynamics and probe extensions to the Standard Model of particle physics. I will present two new measurements of the electron magnetic moment. The second, at a relative uncertainty of 0.28 parts-per-trillion, yields a value of the fine structure constant with a relative accuracy of 0.37 parts-per-billion, over 10-times smaller uncertainty than the next-best methods.

Cavity Control in a Single-Electron Quantum Cyclotron: An Improved Measurement of the Electron Magnetic Moment – David Hanneke Thu. May 13th, 2010
4:15 pm-5:15 pm

Measurements of the electron magnetic moment (the “g-value”) probe the electron’s interaction with the fluctuating vacuum. With a quantum electrodynamics calculation, they provide the most accurate determination of the fine structure constant. Comparisons with independent determinations of the fine structure constant are the most precise tests of quantum electrodynamics and probe extensions to the Standard Model of particle physics. I will present two new measurements of the electron magnetic moment. The second, at a relative uncertainty of 0.28 parts-per-trillion, yields a value of the fine structure constant with a relative accuracy of 0.37 parts-per-billion, over 10-times smaller uncertainty than the next-best methods.

Michelson Lectures — Optical Atomic Clocks – David Hanneke Tue. May 11th, 2010
11:30 am-12:30 pm

The most precise measurement techniques involve time, frequency, or a frequency ratio. For example, for centuries, accurate navigation has relied on precise timekeeping — a trend that continues with today’s global positioning system. After briefly reviewing the current microwave frequency standards based on the hyperfine structure of cesium, I will describe work towards atomic clocks working at optical frequencies. Among these are standards based on trapped ions or on neutral atoms trapped in an optical lattice. A frequency comb allows the comparison of different optical frequencies and the linking of optical frequencies to more-easily-counted microwave ones. Though still in the basic research stage,

Michelson Postdoctoral Lecture 2:Optical Atomic Clocks – David Hanneke Tue. May 11th, 2010
12:30 pm-1:30 pm

The most precise measurement techniques involve time, frequency, or a frequency ratio. For example, for centuries, accurate navigation has relied on precise timekeeping — a trend that continues with today’s global positioning system. After briefly reviewing the current microwave frequency standards based on the hyperfine structure of cesium, I will describe work towards atomic clocks working at optical frequencies. Among these are standards based on trapped ions or on neutral atoms trapped in an optical lattice. A frequency comb allows the comparison of different optical frequencies and the linking of optical frequencies to more-easily-counted microwave ones. Though still in the basic research stage,

Optical Atomic Clocks – David Hanneke Tue. May 11th, 2010
12:30 pm-1:30 pm

The most precise measurement techniques involve time, frequency, or a frequency ratio. For example, for centuries, accurate navigation has relied on precise timekeeping — a trend that continues with today’s global positioning system. After briefly reviewing the current microwave frequency standards based on the hyperfine structure of cesium, I will describe work towards atomic clocks working at optical frequencies. Among these are standards based on trapped ions or on neutral atoms trapped in an optical lattice. A frequency comb allows the comparison of different optical frequencies and the linking of optical frequencies to more-easily-counted microwave ones. Though still in the basic research stage,

Michelson Lectures — Entangled Mechanical Oscillators and a Programmable Quantum Computer: Adventures in Coupling Two-Level Systems to Quantum Harmonic Oscillators – David Hanneke Mon. May 10th, 2010
11:30 am-12:30 pm

The two-level system and the harmonic oscillator are among the simplest analyzed with quantum mechanics, yet they display a rich set of behaviors. Quantum information science is based on manipulating the states of two-level systems, called quantum bits or qubits. Coupling two-level systems to harmonic oscillators allows the generation of interesting motional states. When isolated from the environment, trapped atomic ions can take on both of these behaviors. The two-level system is formed from a pair of internal states, which lasers efficiently prepare, manipulate, and read-out. The ions’ motion in the trap is well described as a harmonic oscillator and can be cooled to the quantum ground state.

Michelson Postdoctoral Lecture 1: Entangled Mechanical Oscillators and a Programmable Quantum Computer: Adventures in Coupling Two-Level Systems to Quantum Harmonic Oscillators – David Hanneke Mon. May 10th, 2010
12:30 pm-1:30 pm

The two-level system and the harmonic oscillator are among the simplest analyzed with quantum mechanics, yet they display a rich set of behaviors. Quantum information science is based on manipulating the states of two-level systems, called quantum bits or qubits. Coupling two-level systems to harmonic oscillators allows the generation of interesting motional states. When isolated from the environment, trapped atomic ions can take on both of these behaviors. The two-level system is formed from a pair of internal states, which lasers efficiently prepare, manipulate, and read-out. The ions’ motion in the trap is well described as a harmonic oscillator and can be cooled to the quantum ground state.

Entangled Mechanical Oscillators and a Programmable Quantum Computer: Adventures in Coupling Two-Level Systems to Quantum Harmonic Oscillators – David Hanneke Mon. May 10th, 2010
4:15 pm-5:15 pm

The two-level system and the harmonic oscillator are among the simplest analyzed with quantum mechanics, yet they display a rich set of behaviors. Quantum information science is based on manipulating the states of two-level systems, called quantum bits or qubits. Coupling two-level systems to harmonic oscillators allows the generation of interesting motional states. When isolated from the environment, trapped atomic ions can take on both of these behaviors. The two-level system is formed from a pair of internal states, which lasers efficiently prepare, manipulate, and read-out. The ions’ motion in the trap is well described as a harmonic oscillator and can be cooled to the quantum ground state.

William Herschel and the Invention of Modern Astronomy – Michael D. Lemonick Thu. May 6th, 2010
2:00 pm-3:00 pm

In 1781, William Herschel became the first person in human history to discover a new planet. This feat was enough to make his reputation and enable him to give up his day job to concentrate on the heavens full-time. But he believed–correctly, in retrospect–that it wasn’t nearly as important as his real astronomical work. Working alongside his sister Caroline, William Herschel was the first astronomer to think about the universe in the same way astrophysicists do today.

Understanding and predicting material properties: insight from quantum simulations – Giulia Galli Thu. April 29th, 2010
11:00 am-12:00 pm

We discuss the progress and successes obtained in recent years in predicting fundamental properties of systems in condensed phases and at the nanoscale, using ab-initio, quantum simulations. Our examples will focus on nanostructured materials for opto-electronic, photovoltaic and thermoelectric applications, and on solvation processes in simple aqueous solutions. We will also discuss open issues related to the validation of the approximate, first principles theories used in large scale simulations, and the resulting complex interplay between computation and experiment.

Cosmological Bubbles and Solitons: A Classic(al) Effect – Tom Giblin Tue. April 27th, 2010
11:30 am-12:30 pm

Cosmological bubble collisions arising from first order phase transitions are a generic consequence of the Eternal Inflation scenario. I will present our computational strategy for generating and evolving these bubbles in 3+1 dimensions and in a self-consistently expanding background. I will show the existence of classical field transitions–the classical nucleation of bubbles during collisions–which can dramatically alter the canonical description of eternal inflation.

Atom Mapping and Correlated Functional Imaging of Nanowires – Lincoln J. Lauhon Mon. April 26th, 2010
12:30 pm-1:30 pm

Nanowires are nanoscale in two dimensions and microscale in a third dimension, providing a wealth of opportunities to exploit novel nanoscale electronic, optical, magnetic, and thermal properties in devices with well-defined microscale electrical contacts. An attendant challenge is the establishment of quantitative structure-property relationships that enable rational engineering of new and/or superior function. In semiconductors, the dopant concentration determines the carrier concentration, so correlated studies of dopant distribution and local conductivity are important when intentional or unintentional inhomogeneities are present. In materials that undergo phase-changes near room temperature, such as vanadium oxide (VO2), the crystal structure influences the conductivity, so local mapping of phase domains is important to understanding and controlling switching behaviors.

Organic Spintronics – Valy Vardeny Thu. April 22nd, 2010
4:15 pm-5:15 pm

Organic semiconductors have been used as active layer in devices such as organic light-emitting diodes (OLEDs), photovoltaic cells, field-effect transistors, and lasers. Recently there has been a growing interest in spin and magnetic field effects in these materials. This include optically detected magnetic resonance where long spin coherence time was demonstrated; OLEDs where substantive magneto-electroluminescence and magneto-conductance were obtained; and organic spin valves (OSV) where spin injection from ferromagnetic (FM) electrodes was obtained. The interest in organic semiconductors has been motivated by the weak spin-orbit interaction that is caused by the light building block elements such as carbon and hydrogen,

Controlling Spin and Magnetism in Quantum Dots – Rafal Oszwaldowski Mon. April 19th, 2010
12:30 pm-1:30 pm

A promising approach for the next generation of applications for information storage and processing comes from the field of spintronics (spin-electronics) that seeks to use spin of carriers, rather than just their charge [1]. Commercial spintronic devices, such as computer hard drives, are based on metallic magnetic multilayers, and utilize the magnetic moment associated with spin to read magnetically stored information. Unfortunately, for advanced functions such as signal processing and digital logic, these structures are of limited use, and it would be more desirable to control spin and magnetism in semiconductors. Carrier-mediated magnetism in such semiconductors as (In,Mn)As, (Ga,Mn)As or (Cd,Mn)Te [2],

Water on the Surface of the Moon – Jessica Sunshine (jointly with Astronomy) Thu. April 15th, 2010
4:15 pm-5:15 pm

Although the Moon was widely thought to be anhydrous, OH and H2O absorptions were detected on the lunar surface by infrared spectrometers on three different spacecraft. Complimentary data from Moon Mineralogy Mapper (M-cubed; M3) on Chandrayaan-1, the IR spectrometer on Deep Impact, and VIMS on Cassini have mapped widespread hydration at the 0.1 wt% level. The 140 m scale M3 data reveal differences with composition and maturity, while temporal variations in Deep Impact data show the entire surface to be hydrated during some portions of the day. In particular, comparisons between data collected one week (a quarter lunar day) apart show a dynamic process with diurnal changes in hydration,

Diffusion Tensor Imaging: A Guided Tour – Cheng Guan Koay Thu. April 15th, 2010
12:30 pm-1:30 pm

Diffusion tensor imaging (DTI) is a noninvasive magnetic resonance (MR) technique for investigating tissue microstructure and white matter architectural organization in the brain. In this talk, we will present a basic introduction to DTI and give a guided tour through recent developments in the analysis of diffusion tensors from the least squares estimations of the diffusion tensor to the elliptical cone of uncertainty for characterizing uncertainty of the major eigenvector (or principal axis) of the diffusion tensor.

CP Violation in Bs->J/psi phi: Evidence for New Physics? – Karen Gibson Tue. April 13th, 2010
11:30 am-12:30 pm

CP violation in the Bs->J/psi phi system has been one of the most discussed topics in particle physics in the past two years, in large part due to anomalously high, although statistically limited, measurements of the CP violating phase made by the Tevatron experiments. The measurement of this CP phase has been a highlight of the late Run II Tevatron physics effort and it’s precise determination is the flagship analysis of the LHCb program. I will present the physics interest in CP violation in the Bs system, give an overview of the past and present results from the Tevatron experiments,

Through A Glass, Darkly: Obtaining Quantitative Information from Microscope Images of Liquid Crystals – Tim Atherton Tue. April 13th, 2010
12:30 pm-1:30 pm

Liquid Crystalline phases are identified by their beautiful textures when viewed under the polarizing microscope. These two-dimensional textures contain much information about the ordering of the liquid crystal, but it is generally difficult to extract quantitative information from them since the mapping from the order parameter field to the image is not injective. More sophisticated imaging methods have been developed such as Fluorescence Confocal Microscopy and Near-field Scanning Optical Microscopy, which offer three-dimensional images of LC ordering but nonetheless pose further challenges to their interpretation. In this talk I discuss several examples of how these techniques may be used to reveal the fundamental physics of surface ordering,

Deterministic Isoeffective Dose – Proposal for a New Unit – The Barendsen (Bd) – Barry Wessels, Thu. April 8th, 2010
4:15 pm-5:15 pm
Quantum Effects in Gravitational Collapse of a Reisner-Nordström Domain wall Tue. April 6th, 2010
11:30 am-12:30 pm

We will investigate the formation of RN black holes by studying the collapse of a charged spherically symmetric domain wall. Utilizing the Functional Schrödinger formalism, we will also investigate time-dependent thermodynamic properties of the collapse and compare with the well known theoretical results.

Hard tetrahedra and Quasi-Crystals – Rolfe G. Petschek Mon. April 5th, 2010
12:30 pm-1:30 pm

I will describe the packing of hard tetrahedra. Contrary to recent speculations, Monte Carlo simulations show that at finite temperatures this Platonic solid packs with quite high volume fractions and has very complicated, probably quasi-crystalline phases and (likely) a modestly complicated phase diagram. An analytic high pressure equation of state for hard particles that summarizes this data is given and compared to the simulation data. Interestingly, this system is shown robustly to have an only modestly first order transition from an isotropic fluid to a quasi-crystal (or quasi-crystal-like) structure. Contrary to speculations made two decades ago and not yet contradicted clearly in the literature,

2=1: The Gentle Art of Lying Thu. April 1st, 2010
4:15 pm-5:15 pm

Even talented students struggle with fundamental concepts in mathematics and physics. They cannot reason with graphs and have no feel for physical magnitudes. Their instincts are Aristotelian; in their gut they believe that force is proportional to velocity. With such handicaps in mathematical and physical reasoning, they can learn only by rote. I’ll discuss these difficulties and how the art of approximation can improve our teaching and students’ learning. Students then cannot conceal misconceptions behind mathematical agility, and can enjoy estimating the size of raindrops, the pitches of xylophone slats, or the distance that birds (and 747’s) can fly without refueling.

String theory cosmic strings – Dimitri P. Skliros Tue. March 30th, 2010
11:30 am-12:30 pm

I will discuss the first construction of coherent states in the covariant formalism for both open and closed strings with applications to cosmic strings in mind. Furthermore, I provide an explicit map that relates three different descriptions of cosmic strings: classical strings, lightcone gauge quantum states and covariant vertex operators. I will then go on to discuss applications and future directions: string amplitude computations with such vertices and in particular decays of (the phenomenologically promising) cosmic strings with non-degenerate cusps in a framework that naturally incorporates the effects of gravitational backreaction. Partly based on: http://arxiv.org/abs/0911.5354

Periodic networks in heterogeneous materials: theory and multiscale homogenization for soling heat transfer and deformation problems – Viktoria Savatorova Mon. March 29th, 2010
12:30 pm-1:30 pm

All materials consist of some heterogeneity. In many cases heterogeneity can affect the properties of the whole sample, and this fact stimulates the desire to create heterogeneous materials with definite desired properties. Most of man-made materials such as composite materials, porous structures, powders, have periodical structure. In nature geological materials have structures, close to periodical. This is the reason to investigate the behavior of heterogeneous materials with periodical structure. In the majority of cases heterogeneous materials with a number of components, having different properties, cannot be described by direct considering each of the heterogeneities. The way to avoid intractable problems is to replace the heterogeneous medium by an equivalent homogeneous.

The Origin of the Universe and the Arrow of Time – Sean Carroll Thu. March 25th, 2010
4:15 pm-5:15 pm

Over a century ago, Boltzmann and others provided a microscopic understanding for the tendency of entropy to increase. But this understanding relies ultimately on an empirical fact about cosmology: the early universe had a very low entropy. Why was it like that? Cosmologists aspire to provide a dynamical explanation for the observed state of the universe, but have had very little to say about the dramatic asymmetry between early times and late times. I will argue that the observed breakdown of time-reversal symmetry in statistical mechanics provides good evidence that we live in a multiverse.

Tunneling in Flux Compactifications – Jose Blanco-Pillado Tue. March 23rd, 2010
11:30 am-12:30 pm

We identify instantons representing several different transitions in a field theory toy model for string theory flux compactifications and described the observational signatures of such processes.

Primordial magnetic fields: evolution and observable signatures – Tina Kahniashvili Tue. March 16th, 2010
11:30 am-12:30 pm

I will discuss the evolution of the primordial magnetic field accounting for MHD instabilities in the early Universe. I will address different cosmological signatures of the primordial magnetic fields and will discuss the observational tests to limit the amplitude and correlation length of the magnetic fields, as well as their detection prospects.

The Demographics of Exoplanets – Scott Gaudi Thu. March 4th, 2010
4:15 pm-5:15 pm

The physical processes that govern planet formation, migration, and evolution are imprinted on the orbital element and mass distributions of exoplanets. Theories of planet formation and evolution have matured to the point where specific predictions for these distributions have been made, yet there are relatively few robust comparisons of these predictions with observations. I will discuss the progress and prospects for measuring the demographics of exoplanets using a variety of techniques, emphasizing the importance of homogeneous statistical analyses and proper accounting of selection effects, and highlighting the ability of various techniques to probe complementary regions of parameter space. In particular,

ArDM Experiment – Carmen Carmona Tue. March 2nd, 2010
11:30 am-12:30 pm

The Argon Dark Matter (ArDM) project aims at operating a large noble liquid detector to search for direct evidence of Weakly Interacting Massive Particles (WIMP) as Dark Matter in the universe. It consists on a one-ton liquid argon detector able to read independently ionization charge and scintillation light. I will describe the experimental concept and the physics performance of the ArDM experiment, which is presently under construction and commissioning on surface at CERN.

From the Bottom Up: Self-Assembled One-Dimension Soft Materials – Jiyu Fang Mon. March 1st, 2010
4:15 pm-5:15 pm

Molecular self-assembly mediated by noncovalent bonds is becoming increasingly popular as a “bottom up” approach in forming nano- and meso-scale soft materials. One of the most attractive aspects of this approach is the prospect of assembling structures with molecular precision under experimentally straightforward and inexpensive conditions. This talk will focus on self-assembled chiral lipid tubes, which are promising candidates for drug delivery vehicles. Three issues will be addressed in this talk. First, I will describe the interactions and mechanisms underling chiral lipid assembly based on the structural characterization of lipid tubes. Second, I will discuss the elasticity and buckling instability of lipid tubes under local radial indentation,

A Theory Program to Exploit Weak Gravitational Lensing to Constrain Dark Energy – Andrew Zentner Fri. February 26th, 2010
11:30 am-12:30 pm

Weak gravitational lensing is one of the most promising techniques to constrain the dark energy that drives the contemporary cosmic acceleration. I give an overview of the dark energy problem, focusing on the manner in which weak gravitational lensing can determine the nature of the dark energy. Bringing lensing constraints to fruition is challenging both observationally and theoretically. I will focus on the theoretical challenges. The most demanding of these is to make accurate predictions for the power spectrum of density fluctuations on nonlinear scales, including treatments of baryonic processes such as galaxy formation, that have been neglected in much of the literature.

Dynamical Imaging using Spatial Nonlinearity – Jason W. Fleischer Thu. February 25th, 2010
4:15 pm-5:15 pm

It is well known that one cannot image directly through a nonlinear medium, as intensity-dependent phase changes distort signals as they propagate. For this reason, nearly all nonlinear imaging techniques are point-by-point methods that rely on the frequency dependence of multi-photon effects, such as two-photon fluorescence and harmonic generation. Here, we focus on spatial effects by taking advantage of spatially dependent changes in the index of refraction. In particular, we apply wave mixing to (lensless) imaging by extending digital holography to the nonlinear domain. The method relies on propagation and provides a new means of super-resolution, e.g. by coupling low and high spatial frequencies.

Ultrafast physics in photosynthesis: Mapping sub-nanometer energy flow – Naomi Ginsberg Thu. February 25th, 2010
12:30 pm-1:30 pm

In the first picoseconds of photosynthesis, photoexcitations of chlorophyll molecules are passed through a network of chlorophyll-binding proteins to a charge transfer site, initiating the conversion of absorbed energy to chemical fuels. The remarkably high quantum efficiency of this energy transfer relies on near-field coupling between adjacent chlorophyll molecules and their interaction with protein phonon modes. Using two-dimensional electronic spectroscopy, we track the time-evolution of energy flow in a chlorophyll-protein complex, CP29, found in green plants. The results from these nonlinear four-wave mixing experiments elucidate the role of CP29 as a light harvester and energy conduit by drawing causal relationships between the spatial and electronic configurations of its chlorophyll molecules.

Shedding light on the nature of dark matter with gamma-rays – Jennifer Siegal-Gaskins Tue. February 23rd, 2010
11:30 am-12:30 pm

Detection of gamma rays from the annihilation or decay of dark matter particles is a promising method for identifying dark matter, understanding its intrinsic properties, and mapping its distribution in the universe. I will review recent results from the Fermi Gamma-ray Space Telescope and other experiments and discuss the constraints these place on particle dark matter models. I will also present a novel approach to extracting a dark matter signal from Fermi gamma-ray observations using the energy-dependence of anisotropies in a sky map of the diffuse emission. The sensitivity of this technique and its prospects for robustly identifying a dark matter signal in Fermi data will be discussed.

Non-gaussianities and the Inflationary Initial State – Andrew Tolley Fri. February 19th, 2010
11:30 am-12:30 pm

The potential discovery of primordial non-gaussianities would revolutionize our understanding of early universe cosmology, giving a whole new perspective on the physics responsible for inflation. I will review the different possible physical mechanisms that can give rise to non-gaussianities, and discuss in detail those which are distinctive in telling us about the inflationary quantum state. In particular, I will show how consistency conditions coming from effective field theory can be used to constrain the level of non-gaussianity that we can hope to observe in future data.

Single cell studies using microfluidic devices – Amy Rowat Thu. February 18th, 2010
12:30 pm-1:30 pm

Cells that are genetically identical can exhibit differences in phenotype, however, such variation remains masked in bulk measurements. To capture variability among individual cells, as well as the behavior of subpopulations of cells, requires studies with single cell resolution. Here I will describe a new class of microfluidic devices that enables studies at the single cell level. First, I will describe a microfluidic device that enables measurements of the mechanical properties of individual cells. The ability of cells to deform through narrow spaces is central in physiological contexts ranging from immune response to metastasis. To elucidate the effect of nuclear shape on the deformability of neutrophil cells,

Dark Matter via Many Copies of the Standard Model – Alex Vikman Tue. February 16th, 2010
11:30 am-12:30 pm

Recently it was realized that the strong coupling scale in gravity substantially depends on the number of different quantum fields present in nature. On the other hand, gravity theory with an electroweak strong coupling scale could be responsible for a solution of the hierarchy problem. Consequently it was suggested that possible existence of very many hidden fields could stabilize the mass of Higgs particle. In this talk I review a cosmological scenario based on the assumption that the Standard Model possesses a large number of copies. It is demonstrated that baryons in the hidden copies of the standard model can naturally account for the dark matter.

Structural relaxations beyond the colloidal glass transition – Veronique Trappe Mon. February 15th, 2010
4:15 pm-5:15 pm

Colloidal dispersions consist of small particles that are immersed in a molecular fluid. The particles move by diffusion, driven by the thermal motion of the molecules surrounding them. However, as the particle concentration increases, the diffusion of the particles becomes increasingly hindered due the presence of their neighbors; consequently, the structural relaxation time, describing the time-scale over which the system reconfigures, increases. This structural relaxation time appears to diverge at a critical concentration that defines the colloidal glass transition, where solid-like behavior sets in. We use new dynamic light scattering methods to probe structural relaxation processes of systems composed of deformable spheres extending the range of volume fraction investigated to deeply quenched systems,

Hierarchy in the Phase Space and Dark Matter Astronomy – Niayesh Afshordi Fri. February 12th, 2010
11:30 am-12:30 pm

Understanding small scale structure in the dark matter distribution is important in interpreting many astrophysical observations, as well as dark matter (direct or indirect) detection searches. With this motivation, I introduce a theoretical framework for describing the rich hierarchy of the phase space of cold dark matter haloes, due to gravitationally bound sub-structures, as well as tidal debris and caustics. I then argue that if/when we detect dark matter particles, a new era of Dark Matter Astronomy will be just around the corner.

Imaging coherent electron transport in graphene – Jesse Berezovsky Thu. February 11th, 2010
12:30 pm-1:30 pm

The coherent flow of electrons through a graphene device is an intriguing physical problem, which must be understood for future quantum technologies. We have developed a low-temperature scanning probe technique for mapping the effect of a single movable scatterer on coherent transport in graphene. We obtain images of conductance vs. scatterer position that provide a spatial view of the interference of electron waves that create universal conductance fluctuations and weak localization.

Photonics with Organic-Inorganic Nanostructures – Manfred Eich Mon. February 8th, 2010
4:15 pm-5:15 pm

The presentation will outline the physics of photonic crystals and photonic nanowires employing silicon and organic materials. Dispersion properties and slow light effects will be discussed as well as nonlinear optical phenomena in such structures. Application perspectives in computer industry will be illustrated.

On a Few Challenges in Soft Condensed Matter Physics – Igor Sokolov Thu. February 4th, 2010
4:15 pm-5:15 pm

Soft Condensed Matter (SCM) is a broad area of science, which includes studying liquids, colloids, gels, polymers, foams, biomaterials, etc. The common feature shared by all SCM materials is the energy associated with their behavior, which is comparable with the ambient thermal energy. With the development of new instrumental and modeling base, SCM faces discoveries of new phenomena, and consequently, new challenges of their understanding. In this talk, I will describe several of such challenges, and focus on two of them, the challenges we came across recently. The first challenge is the understanding of abnormally slow diffusion in silica nanochannels (nanotubes).

Shading Lambda – Claudia de Rahm Tue. February 2nd, 2010
11:30 am-12:30 pm

The idea of degravitation is to tackle the cosmological constant problem by modifying gravity at large distances such that a large cosmological constant does not backreact as much as anticipated from standard General Relativity. After reviewing the fundamental aspects of degravitation, I will present a new class of theories of massive gravity capable of exihibiting the degravitation behaviour. I will then comment on the stability of such models and show in the decoupling limit how theories of gravity with at least two additional helicity-0 excitations can provide a stable realization of degravitation.

Principles and Applications of Extrinsic (Doped) Organic Semiconductors – Calvin Chan Mon. February 1st, 2010
12:30 pm-1:30 pm

Organic semiconductors have garnered much attention for many promising applications, including organic light-emitting diodes, photovoltaic cells, thin-film transistors, thin-film batteries and spintronic devices. Despite this demand, robust and efficient organic electronic devices have been limited by the quality of organic semiconductor materials and a poor understanding of their underlying physics. Extrinsically doped organic semiconductors provide an avenue to overcoming the intrinsic material limitations that impede device performance. Moreover, fundamental doping studies provide insight into the nature of molecular charge transfer between organic moieties. For example, host molecules doped with highly electropositive donor species result in pronounced shifts of the Fermi-level towards the unoccupied molecular states [1].

Dark Matter Substructure in the Milky Way: Properties and Detection Prospects – Louie Strigari Tue. January 26th, 2010
11:30 am-12:30 pm

Cosmological observations have converged on a standard model of Lambda-Cold Dark Matter (LCDM), in which the Universe is dominated by yet unknown components of dark matter and dark energy. When confronted with observations of our own Milky Way, this theory of LCDM leads to the prediction of a significant population of bound, unseen dark matter substructures, ranging possibly from Earth mass scales up to observed dwarf galaxy mass scales. In this talk, I will discuss the theory of LCDM and substructure in the context of present and forthcoming deep galaxy surveys, and show how these observations may be used to provide detailed predictions for the abundance and mass spectrum of dark substructures.

Gigahertz dynamics of a strongly driven single spin in diamond – G. D. Fuchs Mon. January 25th, 2010
12:30 pm-1:30 pm

Nitrogen vacancy (NV) center spins in diamond have emerged as a promising solid-state system for quantum information and communication. Techniques to manipulate a single spin have been used to study the long room temperature spin coherence times of NV centers as well as their interactions with nearby electron and nuclear spins. There remain major challenges, however, both in understanding the physics of these defects and in the development of technologies based on their quantum properties. We extend coherent control of individual spins to the chip level by fabricating coplanar waveguide structures on diamond substrates to apply high-intensity microwave fields. Within large driving fields,

Effects of osmotic stress on DNA packing and capsid stability in simple viruses – Rudi Podgornik Thu. January 21st, 2010
4:15 pm-5:15 pm

I will address the problem of DNA packing in the bacteriophage capsid. I will show that it can be formulated in the framewrok of a liquid crystalline nematic nanodrop model. The elastic equilibrium condition can be written as a first intergral of the EL equations and gives the elastic stresses in the system. Solving the first integral for the DNA density field leads to the encapsidation equation of state that compares well with osmotic stress experiments and predicts the ejection characteristics in the presence of polyvalent counterions. I will also discuss the effects of osmotic stress on empty viral capsids and show that there exists a critcal value of the osmotic stress that destabilizes the capsid.

On triviality of $\lambda\phi^{4}$ theory in $D=4$ – Dmitry Podolsky Tue. January 19th, 2010
11:30 am-12:30 pm

e introduce a new non-perturbative method suitable for analyzing scalar quantum field theories at strong coupling based on mapping between quantum field theories in $dS_{D}\times M_{N}$ spacetime and statistical field theories in Euclidean space $M_{N}$. Applying this method to $\lambda\phi^{4}$ theory in $dS_{D}\times E_{4}$ spacetime, we analyze behavior of the 4-dimensional $\lambda\phi^{4}$ theory in the regime $\lambda\sim{}1$ and give a new argument in favor of triviality of the theory.

The 2009 Nobel (Sciences) Prize-fest – Kathy Kash, William Merrick, Ken Singer, and Derek Taylor Thu. January 14th, 2010
4:15 pm-5:15 pm

Come hear about the Nobel prizes in Chemistry, Medicine or Physiology, and Physics from local experts.

ZnGeAs2: A Novel Semiconductor for Photovoltaics – Tim Peshek Mon. January 4th, 2010
12:30 pm-1:30 pm

> I will motivate the fabrication of tandem thin film devices based solely on II-IV-V2 compounds as a target for wide-scale PV deployment. Third generation solar cells must overcome the Shockley-Queisser (SQ) limitation of single diode solar cells; the fabrication of multiple junction solar cells is one avenue to circumvent the SQ limit. Currently, the high cost of highly efficient multiple junction cells (e.g. the >40% efficient Ge/GaAs/InGaP triple junction) prohibits these devices from being widely deployed in the market. The challenge to condensed matter physics is to identify semiconductors that have optimal properties for multi-junction cells, including material abundance and low manufacturing costs.

Spin Fluctuations in Magnetic Quantum Dots – Andre Petukhov Mon. December 14th, 2009
12:30 pm-1:30 pm
Pulsar Kicks With Active and Sterile Neutrinos – Leonard Kisslinger Fri. December 4th, 2009
11:30 am-12:30 pm

In 2007 my coworkers and I completed the calculation of the velocity given to a neutron star in the period of 10-20 seconds after the gravitational collapse of a massive star by active neutrinos. This year an analysis of neutrino data has shown that there exist sterile neutrinos with large mixing angles. We have calculated the velocity that the emission of such sterile neutrinos in the 0-10 second period would give to the neutron star (the pulsar). We are applying this to calculate the velocity of the neutron star that might have been formed by SN 1987A. We are also engaged in calculating sterile neutrino prosesses during a supernova collapse to see if the stalled shock can be unstalled.

Dynamical Processes in Extrasolar Planetary Systems – Fred Adams Thu. December 3rd, 2009
4:15 pm-5:15 pm

Over the past decade, observations have sparked a renaissance of planetary studies, with nearly 400 planets discovered in orbit about external stars and an ever-increasing inventory of our solar system. These planetary systems display an unexpected diversity in their observed orbits and in the types of bodies found. This wealth of new data poses a number of dynamical issues that will be discussed in this talk: How do planets migrate from one location in a solar system to another, and how does migration ultimately produce the observed distribution of orbital elements? How does turbulence, which provides stochastic forcing, affect both early migration of planetary cores and the maintenence of mean motion resonance?

Quantum Simulation of Strongly Correlated Quantum Dots Out of Equilibrium – Jong Han Mon. November 30th, 2009
12:30 pm-1:30 pm

The study of strong correlation physics out of equilibrium has become one of the most exciting fields in condensed matter theory of today. The physical systems of interest include quantum dots displaying the zero-bias-anomaly (ZBA) due to the Kondo phenomena. Recently, significant progress has been made in the strong-correlation community toward deeper understanding of nonequilibrium many-body state of nanoscale electronic devices under finite source-drain bias. I introduce the recently formulated imaginary-time theory of steady-state nonequilibrium which extends the equilibrium theory into nonequilibrium by introducing complex chemical potentials. Due to its similarity to the equilibrium theory, this formalism becomes very powerful when combined with equilibrium tools such as quantum Monte Carlo method.

Nongaussian Fluctuations from Particle Production During Inflation – Neil Barnaby Tue. November 24th, 2009
11:30 am-12:30 pm

In a variety of inflation models, the motion of the inflaton may trigger the production of some iso-curvature particles during inflation, for example via parametric resonance or a phase transition. Inflationary particle production provides a new mechanism for generating cosmological perturbations (infra-red cascading) and can also slow the motion of the inflaton on a steep potential. Moreover, such models provide a novel example of non-decoupling of high scale physics during inflation. I will discuss the observational consequences of inflationary particle production, including the generation of features in the primordial power spectrum and large nongaussianities with a unique shape of bispectrum.

Probing electrons in a flatland: optical spectroscopy of graphene – Jie Shan Thu. November 19th, 2009
4:15 pm-5:15 pm

Graphene, a single atomic layer of sp2-hybridized carbon atoms, has been the subject of intense scientific interest recently. Many of the most intriguing transport and optical properties of graphene relate directly to its two-dimensional (2D) electronic band structure, with its linear dispersion relation for the low-energy excitations near the K-point of the Brillion zone. Optical Spectroscopy provides a powerful tool to probe the structure of electronic excitations in graphene. In this talk I will review some of the basic properties of this novel material. I will then report several optical studies that I have been involved in the past year during my sabbatical at Columbia University.

The Uncanny Physics of Superhero Comic Books – James Kakalios Thu. November 12th, 2009
4:15 pm-5:15 pm

While it is not quite true that one can learn physics from superhero comic books, it is the motivation for a Freshman Seminar class I teach at the University of Minnesota entitled: “Everything I Know About Science I Learned from Reading Comic Books”. This class covers everything from Isaac Newton to the transistor, but there’s not an inclined plane or pulley in sight. Rather, ALL the examples come from superhero comic books, and as much as possible, those cases where the superheroes get their physics right! For example, have you ever wondered how strong you would have to be to “leap a tall building in a single bound?”

Gravitational Waves, Laser Interferometers and Multimessenger Astrophysics – Laura Cadonati Tue. November 10th, 2009
11:30 am-12:30 pm

The Laser Interferometer Gravitational-wave Observatory (LIGO) and its sister project Virgo are currently acquiring data, aiming at the first direct detection of gravitational waves. These elusive ripples in the fabric of space-time, carriers of information on the acceleration of large masses, are a key prediction of General Relativity; their detection will activate a fundamental, new probe into the universe. Sources of interest for LIGO/Virgo include the coalescence of compact binary systems, core-collapse supernovae and the stochastic background from the early universe, as well as multi-messenger coincident signatures with electromagnetic or neutrino counterparts. In this talk, I will present the status of ground-based gravitational wave detectors and review the most significant observational results obtained so far.

From Water Splitting to Hydrogen Storage: The Art of First-Principles Predictions in Materials Design – Shengbai Zhang Mon. November 9th, 2009
12:30 pm-1:30 pm

Green and renewable energy is important to our environment, for sustainable energy supply, and offers new opportunities for economical growth. In the past, materials research has played an essential role in the development of the science bases necessary for green energy technology. In this talk, I will discuss two recent examples using first-principles density functional theory to predict new materials that are relevant to our energy mission. In particular, I will discuss how to optimize the electronic structures of titanium oxide for water splitting using unconventional codoping. I will also discuss using graphene oxide as a light substrate to anchor transition metal element for enhanced binding to non-polar molecules such as the dihydrogen for room-temperature storage in solids.

Neutrino Physics Beyond SNO – Mark Chen Thu. November 5th, 2009
4:15 pm-5:15 pm

A follow-up experiment to the Sudbury Neutrino Observatory is being developed, called SNO+. With a liquid scintillator replacing the heavy water, SNO+ will examine neutrino phenomena at lower energies than SNO. Physics goals include: detecting the CNO solar neutrinos and using them to resolve a new puzzle related to solar chemical composition; precision measurements of the survival probability of pep solar neutrinos at the transition energy between vacuum- and matter-dominated oscillations; and measuring the flux of geo-neutrinos at a detector site where the local geology has been extensively characterized, enabling the measurement to address fundamental questions in geoscience. We also plan to add neodymium to the SNO+ liquid scintillator in order to perform a competitive next-generation 0-nu double beta decay search.

Three thoughts about black holes and cosmology – Latham Boyle Tue. November 3rd, 2009
11:30 am-12:30 pm

I will present three ideas about black holes and cosmology. First, I will discuss a way of understanding the simple patterns which emerge from the notoriously thorny numerical simulations of binary black hole merger, and some of the directions where this understanding may lead. Second, I will suggest a sequence of practical bootstrap tests designed to give sharp observational confirmation of the essential idea underlying the inflationary paradigm: that the universe underwent a period of accelerated expansion followed by a long period of decelerated expansion. Third, I will investigate a way that one might try to detect the strong bending of light rays in the vicinity of a black hole.

Quantum Mechanics of Point Defects and Diffusion in α-Al2O3 – Arthur Heuer Mon. November 2nd, 2009
12:30 pm-1:30 pm

Ab-initio DFT calculations have been made of native point defects – aluminum vacancies and interstitials and oxygen vacancies and interstitials – and point defect clusters, in both pure sapphire (α-Al2O3) and sapphire doped with the aliovalent solutes Mg and Ti. These calculations have been carried out by and in collaboration with Hine, Frensch, Finnis and Foulkes of Imperial College, London and have resolved the corundum “conundrum” (corundum is the mineral name forα-Al2O3 . The conundrum in question is the “buffering” evident in self-diffusion data of pure and doped crystals and how to interpret the sizeable activation energy found experimentally for oxygen diffusion.

Computer Simulations of Self-Assembly of Metallo-Supramolecular Networks – Elena Dormidontova Sat. October 31st, 2009
12:30 pm-1:30 pm

Using Monte Carlo simulations we studied formation of reversible metallo-supramolecular networks based on 3:1 ligand-metal complexes between end-functionalized oligomers and metal ions. The fraction of 1:1, 2:1 and 3:1 ligand-metal complexes in reversibly associated structures was analyzed as a function of oligomer concentration, c and metal-to-oligomer ratio. We studied the onset of network formation, which occurs in a limited range of metal-to-oligomer ratios at sufficiently large oligomer concentrations as well as the properties of metallo-supramolecular networks. We found that the mesh size of the network decreases with oligomer concentration and reaches its minimum at the stoichiometric composition, where the high-frequency elastic plateau modulus approaches its maximal value.

Close Encounters with the Quantum Berry Phase – Hari Manoharan Thu. October 29th, 2009
4:15 pm-5:15 pm

If we deform a material and restore it precisely back to its starting point, our everyday intuition tells us that the material before and afterwards is identical. This is true classically, and was believed to be true quantum mechanically until recently. Even if all the atoms, electrons, and other ingredients are returned exactly to where they started, we now know that the restored material can differ from the undeformed material by nontrivial quantum mechanical phase factors. The importance of these so-called geometric or Berry phases has garnered increasing appreciation and attention in recent years. The quantum Berry phase can fundamentally alter the ground state of a system,

Magnetic Properties of Rare Earth Doped GaN – John M. Zavada Mon. October 26th, 2009
12:30 pm-1:30 pm

Rare earth (RE) doped GaN has been widely investigated for applications in displays and optical applications due to the strong visible infared (IRR) emissions from RE3+ ions in such a wide-band-gap material. In recent years this material systems has also beome an importatn candidate as a dilute magnetic semiconductor (DMS). Room temperature ferromagnetism has been observed in GaN doped with different REs inclouding Gd, Eu and Er. However, considerbable debate continues as to the origin of this ferromagnetic behavior. Thsi talk will focus on research concerning the magnetic properties of RE doped GaN films and the claim it is a DMS material.

Fermi Gamma-ray Space Telescope: The First Year – Peter Michelson Thu. October 22nd, 2009
4:15 pm-5:15 pm

The Fermi Gamma-ray Space Telescope has completed its first year of observations. The two instruments on Fermi cover more than 7 decades in energy: the Large Area Telescope (LAT) is a wide field-of-view pair-conversion telescope covering the energy range from 20 MeV to more than 300 GeV; the Gamma-ray Burst Monitor complements the LAT in its observations of transient sources and is sensitive to X-rays and g-rays with energies between 8 keV and 40 MeV. During the first year in orbit, Fermi has continually surveyed the entire sky every 3 hours and observed a large number of sources that include active galaxies,

Using anisotropy to identify a dark matter signal in diffuse gamma-ray emission with Fermi – Jennifer Siegal-Gaskins Tue. October 20th, 2009
11:30 am-12:30 pm

Dark matter annihilation in Galactic substructure will produce diffuse gamma-ray emission of remarkably constant intensity across the sky, making it difficult to disentangle this Galactic dark matter signal from the extragalactic gamma-ray background. Recent studies have considered the angular power spectrum of the diffuse emission from various extragalactic source classes and from Galactic dark matter. I’ll discuss these results and show how the energy dependence of anisotropies in the total measured diffuse emission could be used to confidently identify a signal from dark matter in Fermi data. Finally, I’ll present new results demonstrating that anisotropy analysis could significantly extend the sensitivity of current indirect dark matter searches.

Nanoscale memristive devices for memory and logic applications – Wei Lu Mon. October 19th, 2009
12:30 pm-1:30 pm

Memristor (a word created from “memory” and “resistor” ) has been claimed as the ” missing circuit element”and research on nanoscale memristor devices has gained substantial interest recently after the development of a simple device model last year. Memristors or memristive systems are two-terminal electrical switches that exhibit both hysteresis (memory) and non-linear resistance characteristics. These properties allow them to act as promising candidates for ultra-high density memory and logic applications. In this talk, I will discuss our studies on a silicon-based memristive system. As a digital memory, the device is fully compatible with CMOS processing and exhibits excellent performance in terms of scaling potential,

Measuring small scale CMB temperature and polarization anisotropies with the Atacama Cosmology Telescope – Mike Niemack Fri. October 16th, 2009
11:30 am-12:30 pm

The Atacama Cosmology Telescope (ACT) is a six-meter telescope on the Atacama plateau, Chile that was built to characterize the cosmic microwave background (CMB) with arcminute resolution. Since 2008 ACT has been used to measure the temperature anisotropies in the CMB in three bands between 140 – 300 GHz with the largest arrays of transition-edge sensor (TES) bolometers ever fielded for CMB observations. Two of the primary science objectives for these measurements are: detecting galaxy clusters via the Sunyaev-Zel’dovich effect, which can be used to study the dark energy equation of state when combined with optical redshifts, and measuring the CMB power spectrum at high multipoles to improve constraints on cosmological parameters.

Weighing the Universe – Neta Bahcall Thu. October 15th, 2009
4:15 pm-5:15 pm

How do we weigh the Universe? Where is the Dark Matter? I will discuss these questions and show that several independent methods, including the observed abundance of rich clusters , the baryon-fraction in clusters, the observed Mass-to-Light function from galaxies to superclusters, and other large-scale structure observations, all reveal a universe with a low mass density of ~20% of the critical density. The data suggest that the mass in the Universe, including the dark-matter, follows light on large scales, and most of the mass resides in huge dark halos around galaxies. I will review the combined observational evidence for dark-matter and for dark-energy in the universe and their cosmological implications.

A birds-eye view of nonlinear optics: using scale invariance to optimize the molecular response – Mark Kuzyk Wed. October 14th, 2009
12:30 pm-1:30 pm

Nonlinear optical materials show great promise in a broad range of applications from cancer therapies and medical imaging to increasing the speed of the internet. Making such applications possible requires molecules that interact more strongly with light. After more than three decades of research, many new molecules have been synthesized with larger nonlinear response, made larger mainly by increasing the number of electrons and decreasing the energy gap; but, the best molecules have remained a factor of 30 below the fundamental limit. I will discus how the fundamental limits and scale invariance are applied to the design of better molecules.

New Perspectives on Indirect, Astrophysical Dark Matter Limits – Andrew Zentner Fri. October 9th, 2009
11:30 am-12:30 pm

High-Energy neutrinos from the annihilations of dark matter captured within the Sun is thought to be a relatively clean, indirect probe of dark matter physics. In addition, this probe is sensitive to the dark matter-proton cross section so it can be used to cross-check direct searches, and does not rely on a large annihilation cross section in order to be observed in near-term experiments such as IceCube. I will consider a modification of the standard scenario. Dark matter that interacts strongly with itself as has been proposed in several contexts. I show that viable models of self-interacting dark matter can lead to large boosts in the expected neutrino flux from the Sun,

How RNA helicases unwind – Eckhard Jankowsky Thu. October 8th, 2009
4:15 pm-5:15 pm

Virtually all aspects of RNA metabolism involve RNA helicases, enzymes that remodel RNA and RNA-protein complexes in an ATP-dependent fashion. How RNA helicases catalyze such reactions is a key question in RNA metabolism, with implications ranging from understanding the regulation of gene expression to delineating the cellular response to viral infections. In this seminar, I will present recent results that illuminate how different RNA helicases couple ATP binding and hydrolysis to RNA duplex unwinding. Our data reveal a remarkable diversity of unwinding mechanisms among these enzymes.

Thermal Transport and Thermoelectric Energy Conversion in Nanomaterials – Li Shi Mon. October 5th, 2009
12:30 pm-1:30 pm

The high charge carrier mobility and thermal conductivity of carbon nanotubes and graphene have attracted interest in their applications for nanoelectronics and thermal management. On the other hand, the suppressed lattice thermal conductivity of semiconducting nanowires and thin films may give rise to enhanced figure of merit of thermoelectric materials. In an effort to better understand the potentials and challenges of these nanomaterials-enabled designs, we have developed a set of experimental methods to characterize electron and phonon transports in individual nanostructures. Our recent experiments have demonstrated the measurement of the thermal conductance together with the chirality of the same individual single- walled carbon nanotube,

Combining computation and experiment to accelerate the discovery of new hydrogen storage materials – Donald J. Siegel Thu. October 1st, 2009
4:15 pm-5:15 pm

The potential of emerging technologies such as fuel cells (FCs) and photovoltaics for environmentally-benign power generation and conversion has sparked intense interest in the development of new materials for high density energy storage. For applications in the transportation sector, the demands placed upon energy storage media are especially stringent, as a potential replacement for internal combustion engines — the PEM FC — requires hydrogen as a fuel. Although hydrogen has about three times the energy density of gasoline by weight, its volumetric energy density (even at 700 bar) is roughly a factor of six smaller. Consequently, the safe and efficient storage of hydrogen has been identified as one of the key challenges to realizing a transition to FC vehicles.

Band structure information from soft x-ray spectroscopy – Andrew Preston Mon. September 28th, 2009
12:30 pm-1:30 pm

The optical and electric properties of a material are entirely dependent on the ordering of its electrons. In crystalline materials quantum effects constrain the electrons to bands that are best described in terms of crystal momentum. It is this electronic “band structure” we need to understand in order to fully harness novel materials. Soft x-ray based spectroscopic techniques provide a way to directly measure electronic band structures. In this talk I will present an overview of synchrotron based x-ray absorption, emission, photoemission, and resonant emission spectroscopy. Focusing on zinc oxide – a transparent conducting oxide with numerous potential applications –

A van der Waals DFT Approach to Modeling Water – Timo Thonhauser Thu. September 24th, 2009
4:15 pm-5:15 pm

In this colloquium I will discuss my recent work in electronic-structure theory, which allows us to more accurately study water from first-principles. First, I will address a shortcoming of standard density functional theory, which gives poor results for systems with van der Waals interactions such as bulk water. To remedy the situation, I will introduce a new exchange-correlation functional that includes van der Waals interactions in a seamless manner. The main advantage of our approach is the much more favorable scaling of the computational expense compared to standard quantum-chemistry approaches. Second, I will present a Wannier-function approach to derive a fully quantum-mechanical theory for the orbital magnetization in periodic crystals,

CMB Polarization Power Spectra from Two Years of BICEP Data – Cynthia Chiang Tue. September 22nd, 2009
11:30 am-12:30 pm

BICEP is a bolometric polarimeter designed to measure the inflationary B-mode polarization of the cosmic microwave background at degree angular scales. During three seasons of observing at the South Pole (2006–2008), BICEP mapped ~2% of the sky chosen to be uniquely clean of polarized foreground emission. I will discuss the initial maps and angular power spectra derived from a subset of the data acquired during the first two years, and I will describe in detail the analysis methods and studies of potential systematic errors. BICEP measures the E-mode power spectrum with high precision at 21 < ell < 335 and detects the acoustic peak expected at ell ~ 140 for the first time.

Formation and properties of Cu_2S-CdS and Ag_2S-CdS Nanorod Heterostructures – Denis Demchenko Mon. September 21st, 2009
12:30 pm-1:30 pm

A partial cation exchange has been used to synthesize Cu_2S-CdS and Ag_2S-CdS nanocrystal heterostructures, with two very different morphologies. Cu^+ cation exchange takes place preferentially at the ends of CdS nanorods, Cu_2S segments grow into the nanorod from both ends. Ag^+ exchange is non-selective, Ag_2S islands nucleate and grow over the entire surface of the nanorod. This leads to very different patterns, striped Ag_2S-CdS superlattice with several equidistant Ag_2S segments in a CdS nanorod, and an asymmetric Cu_2S-CdS heterostructure with Cu_2S segments at the ends of the CdS nanorod. We use first-principles calculations to explain the formation patterns in the two nanostructures,

Dots for Dummies – Ramamurti Shankar Thu. September 17th, 2009
4:15 pm-5:15 pm

I will provide an introduction to quantum dots, a problem where disorder, interactions and finite size combine to make a perfect storm. Yet it is just this combination that makes an exact solution possible. I will describe that solution and give an introduction to the tools used: renormalization group and random Matrix Theory.

Recent Advances in Organic (Opto)electronic Materials – Oksana Ostroverkhova Wed. September 16th, 2009
12:30 pm-1:30 pm

There is growing interest in using organic (opto)electronic materials for applications in electronics and photonics. In particular, organic semiconductor thin films offer several advantages over traditional silicon technology, including low-cost processing, the potential for large-area flexible devices, high-efficiency light emission, and widely tunable properties through functionalization of the molecules. Over the past decade, remarkable progress in materials design and purification has been made, which led to applications of organic semiconductors in light-emitting diodes, polymer lasers, photovoltaic cells, high-speed photodetectors, organic thin-film transistors, holographic displays, and many others. Most of the applications envisioned for organic semiconductors rely on their (photo)conductive and/or luminescent properties.

When Coal was an Alternative Energy: Engineering, Efficiency, and American Foreign Relations in the Age of Steam – Peter Shulman Thu. September 10th, 2009
4:15 pm-5:15 pm

This talk examines how American foreign relations and national security between 1840 and 1920 were shaped by developments in geology, steam engineering, and the science of logistics. At the same time, technical experts trained their research on the combustion and distribution of coal, the design of steam engines, and the rational management of resources to address new challenges faced by the United States’ growing power in world affairs. This history examines how a new energy technology answered old problems while creating new ones.

How the CMB challenges cosmology’s standard model – Glenn Starkman Thu. September 3rd, 2009
4:15 pm-5:15 pm

The Cosmic Microwave Background Radiation is our most important source of information about the early universe. Many of its features are in good agreement with the predictions of the so-called standard model of cosmology — the Lambda Cold Dark Matter Inflationary Big Bang. However, the large-angle correlations of the microwave background exhibit several closely related statistically significant departures from the standard model. The lowest multipoles seem to be correlated with each other, rather than statistically independent as inflationary theory demands. Indeed, they also seem to be correlated with the geometry of the solar system, suggesting that they are not cosmologically produced.

LUX, LZ, and the Limits of our Ability to Directly Detect Dark Matter – Tom Shutt Thu. August 27th, 2009
4:15 pm-5:15 pm

Overwhelming cosmological and astrophysical evidence suggests that the dominant mass in the universe is in the form of as-yet-unidentified dark matter. The most favored candidate for dark matter is weakly interacting particles (WIMPs), which are also a generic prediction in supersymmetry. WIMPs in our galaxy can be measured by their interactions in detectors operated deep underground with backgrounds from radioactive and cosmic-rays suppressed by some 10 orders of magnitude from ambient levels. Recent advances in detectors based on liquified noble elements promise a radical increase in the sensitivity of these experiments, and will allow a nearly complete test of supersymmetric dark matter in the next decade.

Ballistic Quasiparticles in Superfluid 3He: A Non-Newtonian Gas – George Pickett Mon. May 18th, 2009
12:30 pm-1:30 pm

We can cool superfluid 3He to below 100 microkelvin where the number of unpaired 3He atoms is only of the order of 1 in 10^8. Here these quasiparticle excitations move ballistically as they are so tenuous that collisions are highly improbable. This dilute gas has very strange properties, since the Bardeen-Cooper-Schrieffer dispersion curve is quite unlike that for a classical gas. This makes the dynamics very unusual since even at the lowest temperatures and smallest quasiparticle energies the momentum they carry is very large. That means that we can detect this gas by its damping effect on a mechanical resonator even though by room temperature standards it would represent a reasonably good vacuum.

Cryogenic Dark Matter Search . Current Results and Future Background Discrimination – Cathy Bailey Tue. May 5th, 2009
11:30 am-12:30 pm

The Cryogenic Dark Matter Search (CDMS) is searching for Weakly Interacting Massive Particles (WIMPs) with cryogenic germanium particle detectors. These detectors discriminate between nuclear recoil candidate and electron recoil background events by collecting both phonon and ionization energy from recoils in the detector crystals. The CDMS II experiment has completed analysis of the first data run with 30 semiconductor detectors at the Soudan Underground Laboratory resulting in a world leading WIMP-nucleon spin-independent cross section limit for WIMP masses above 44 GeV/c2. As CDMS aims to achieve greater WIMP sensitivity, it is necessary to increase the detector mass and discrimination between signal and background events.

Chirality and Kondo Physics in Graphene – Herb Fertig Mon. April 27th, 2009
12:30 pm-1:30 pm

Graphene, a two-dimensional network of carbon atoms, exhibits unique electronic properties because it supports low energy, massless, Dirac-like quasiparticles. The quantized Hall effect in this system has an unusual set of plateaus, whose locations may be interpreted in terms of a geometric “Berry’s phase” related to the chirality of the Dirac particles. The chiral nature of these states also leads to an unusual edge state structure, particularly near filling factor nu=0. We examine the transport behavior of the nu=0 graphene system in light of its unusual edge state structure. When electron-electrons interactions are included, we find a magnetic domain wall structure at the edge that is electrically conducting and behaves like a Luttinger liquid.

String shots from a spinning black hole – Ted Jacobson Fri. April 24th, 2009
11:30 am-12:30 pm

The dynamics of relativistic current carrying string loops moving axisymmetrically on the background of a Kerr black hole are characterized. In one interesting type of motion, a loop can be ejected along the axis, some internal elastic or rotational kinetic energy being converted into translational kinetic energy.

Making sense of non-Hermitian Hamiltonians – Carl Bender Thu. April 23rd, 2009
4:15 pm-5:15 pm

The average quantum physicist on the street believes that a quantum-mechanical Hamiltonian must be Dirac Hermitian (symmetric under combined matrix transposition and complex conjugation) in order to be sure that the energy eigenvalues are real and that time evolution is unitary. However, the Hamiltonian $H=p^2+ix^3$, for example, which is clearly not Dirac Hermitian, has a real positive discrete spectrum and generates unitary time evolution, and thus it defines a perfectly acceptable quantum mechanics. Evidently, the axiom of Dirac Hermiticity is too restrictive. While the Hamiltonian $H=p^2+ix^3$ is not Dirac Hermitian, it is PT symmetric; that is, it is symmetric under combined space reflection P and time reversal T.

Landau Level Spectroscopy of Graphene – Zhigang Jiang Mon. April 20th, 2009
12:30 pm-1:30 pm

Graphene, a single atomic sheet of graphite, is a monolayer of carbon atoms arranged in a hexagonal lattice. The unique electronic band structure of graphene exhibits an unusual low-energy linear dispersion relation, radically different from the parabolic bands common to all previous two-dimensional systems. Most interestingly, the charge carriers in graphene mimic relativistic, massless Dirac particles, leading to intriguing new phenomena. In this talk, I focus on two projects related to graphene that complement each other: magneto- transport measurements in high magnetic fields, and infrared optical studies of graphene. In the transport experiments, we discovered a room temperature quantum Hall effect in graphene [1] and new quantum Hall phases in the extreme quantum limit [2,3].

Simulation, signatures and backgrounds at the LHC – Johan Alwall Thu. April 16th, 2009
12:30 pm-1:30 pm

In the final lecture I will go into details of how to distinguish New Physics at the LHC. I introduce Monte Carlo simulation, the standard tool used for data mining at colliders, and then go on to describe different types of signatures we can expect from new physics, and the Standard Model backgrounds mimicking these signatures. I describe how precision simulation can be achieved, both for the Standard Model backgrounds and the New Physics signals, and present some of the simulation tools available in the community, before concluding the lecture series.

Download Johan’s Slides for this talk.

New Physics at the LHC – Johan Alwall Wed. April 15th, 2009
12:30 pm-1:30 pm

In this second lecture, I further discuss the problems with the Standard Model and why there should be new physics beyond the Standard Model. I will present different classes of solutions, including Supersymmetry, Little Higgs models, and models for Extra Dimensions, as well as their general signatures at the LHC. If time allows, I will end with a discussion about recent ideas for new physics which is not directly motivated by the problems of the Standard Model, including Unparticles and Hidden Valley scenarios.

Download Johan’s Slides for this talk.

Fundamentals of the LHC – Johan Alwall Tue. April 14th, 2009
11:30 am-12:30 pm

In this introductory lecture I will present why we have built the LHC, and discuss the underlying physics of a hadron collider. This includes the fundamentals of QCD (the theory for the strong interaction), features such as jets and hadronization, and an introduction to the physics of the Standard Model, including Electroweak symmetry breaking. The lecture will be concluded with a discussion about the problems with the Standard Model.

Fundamentals of the LHC – Johan Alwall Tue. April 14th, 2009
12:30 pm-1:30 pm

In this introductory lecture I will present why we have built the LHC, and discuss the underlying physics of a hadron collider. This includes the fundamentals of QCD (the theory for the strong interaction), features such as jets and hadronization, and an introduction to the physics of the Standard Model, including Electroweak symmetry breaking. The lecture will be concluded with a discussion about the problems with the Standard Model.

Download Johan’s Slides for this talk.

Hunting for New Physics at the Large Hadron Collider – Johan Alwall Mon. April 13th, 2009
4:15 pm-5:15 pm

I discuss different types of New Physics scenarios, their motivation and how to see them at the LHC. I give an overview of the difficulties associated with distinguishing New Physics among the backgrounds from the Standard Model, and finally present some best- and worst-case scenarios for the LHC.

First-principles theory of coloration on WO3 upon charge insertion – Peihong Zhang Mon. April 13th, 2009
12:30 pm-1:30 pm

Electrochromic matrials exchibit reversible and persistent change of the optical properties, hence the color, upon applying an electrical pulse that injects both electrons and compensating ions into the materials. Despite much research effort, a first-principles theory for the coloration mechanism in this material has not emerged. Although the connection between the appartent color of materrials and their optical properties is obvious, so far there has been no calculations of the color of materials from first-principles. In this talk, I will discuss first-principles investigations of the coloration of WO3 upon charge insertion, using sodium tungsten bronze (Na_xWO3) as a model system.

Hunting for New Physics at the LHC – Johan Alwall Mon. April 13th, 2009
4:15 pm-5:15 pm

At this colloquium I discuss different types of New Physics scenarios, their motivation and how to see them at the LHC. I give an overview of the difficulties associated with distinguishing New Physics among the backgrounds from the Standard Model, and finally present some best- and worst-case scenarios for the LHC.

Download Johan’s Slides for this talk.

Higher Temperature Superconductors — Why, Where and How? – Malcolm Beasley Thu. April 9th, 2009
4:15 pm-5:15 pm

There is a growing realization that the present high temperature superconductors will not lead to electric power applications of superconductivity above 77K for fundamental reasons. In this talk we analyze these reasons and the fundamental questions they raise about the possibilities of useful very high temperature superconductors. There is hope, but we must look in the right places.

Screening Plasmonic Materials using Nanopyramidal Arrays – Teri Odom Mon. April 6th, 2009
12:30 pm-1:30 pm

Surface plasmon polaritons (SPPs) are responsible for optical phenomena including negative refraction, surface enhanced Raman scattering, and nanoscale focusing of light. Although many materials support SPPs, the choice of metal for most applications has been based on traditional plasmonic materials such as Ag and Au because there have been no side-by-side comparisons of different materials on well- defined, nanostructured surfaces. This talk will describe a platform that not only enables rapid screening of a wide range of metals under different excitation conditions and dielectric environments but that also can identify unexpected materials for biosensing. Nanopyramidal gratings were used to generate SPP dispersion diagrams for Al,

Optical Nanotomography of Anisotropic Fluids – C. Rosenblatt Thu. April 2nd, 2009
4:15 pm-5:15 pm

The physical properties of anisotropic fluids can be manipulated on very short length scales of 100 nm or less by appropriate treatment of the confining substrate(s). This facilitates the use of ordered fluids, such as liquid crystals, in a variety of applications ranging from displays to switchable optical elements such as gratings and lenses. Future advances will require a full understanding of the liquid crystal’s structure at the nanoscale level. But owing to diffraction limitations, high resolution three dimensional imaging of the fluids’s molecular orientation profile has been beyond the reach of extant optical techniques . Here I present a powerful new imaging approach based on the use of polarized light emitted from a tapered optical fiber to investigate molecular orientation in three dimensions at nanoscale levels.

The curvaton inflationary model, non-Gaussianity and isocurvature – Maria Beltran Tue. March 31st, 2009
11:30 am-12:30 pm

The inflationary paradigm has become one of the most compelling candidates to explain the observed cosmological phenomena. However, the data is still inconclusive about the particular details of the inflationary model. Apart from the basic, single field model, there exists a wide range of currently undistinguishable possibilities for the scalar field number, potential and couplings during the early universe. In this talk I will review one of these extensions of the basic inflationary model, the curvaton model, where at least two scalar fields are present during inflation. I will revisit the constraints on the parameters of the model in light of the results of recent non-Gaussianity analyses and bounds on the cold dark matter isocurvature contribution in the primordial anisotropies of the CMB.

Fast Protonic Conductivity in Crystalline Materials: Highly Sulfonated Aromatics – Yuriy Tolmachev Tue. March 31st, 2009
12:30 pm-1:30 pm

Polymer Electrolyte Fuel Cells are expected to replace internal combustion engines as power sources in transportation during our lifetime. The talk will discuss briefly main issues impeding commercialization of PEFC technology as well as the PEFC research at Kent State. Particular attention will be drawn to the need for high-temperature proton conducting membrane. The rest of the talk deals with our recent discovery of fast protonic conductivity in highly sulfonated arenes and its implications for the development of low-humidity high-temperature PEFC membranes.

Large-Scale Structure in Modified Gravity – Roman Scoccimarro Fri. March 27th, 2009
11:30 am-12:30 pm

Cosmic acceleration may be due to modifications of general relativity (GR) at large scales, rather than dark energy. We use analytic techniques and N-body simulations to find out what observational signatures to expect in brane-induced gravity, with focus on new nonlinear effects not present in GR.

Dark Stars – Katie Freese Tue. March 17th, 2009
11:30 am-12:30 pm

We have proposed that the first phase of stellar evolution in the history of the Universe may be Dark Stars (DS), powered by dark matter heating rather than by nuclear fusion. Weakly Interacting Massive Particles, which may be their own antipartners, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel, with lifetimes from millions to billions of years. We find that the first stars are very bright (a million times solar) diffuse puffy objects during the DS phase,

Cosmology on small scales: the structure of (mostly) dark matter halos [joint colloquium with Astronomy] – Carlos Frenk Thu. March 12th, 2009
4:15 pm-5:15 pm

The standard model of cosmology — the “Lambda cold dark matter” model — is based on the idea that the dark matter is a collisionless elementary particle, probably a supersymmetric particle. This model (which mostly dates back to the 1980s) has been famously verified by observations of the cosmic microwave background radiation and the large-scale distribution of galaxies. However, the model has yet to be tested conclusively on the small scales appropriate to most astronomical objects, such as galaxies and clusters. I will review our current understanding of the distribution of dark matter on small scales which derives largely from large cosmological N-body simulations and I will discuss prospects for detecting dark matter,

Dynamics in the Dark – Andrew Tolley Thu. March 5th, 2009
4:15 pm-5:15 pm

If Dark Energy is dynamical, it would indicate the existence of new physics beyond the standard model coupled to gravity. Just as supersymmetry and large extra dimensions have been invoked to solve the Higgs hierarchy problem, it seems natural that this new physics is tied to whatever resolves the cosmological constant hierarchy problem. I will discuss several proposals that have been put forward in this vein and their possible cosmological implications.

Cascading Gravity and Degravitation – Claudia de Rham Tue. March 3rd, 2009
11:30 am-12:30 pm

Cascading gravity is an explicit realization of the idea of degravitation, where gravity behaves as a high-pass filter. This could explain why a large cosmological constant does not backreact as much as anticipated from standard General Relativity. The model relies on the presence of at least two infinite extra dimensions while our world is confined on a four-dimensional brane. Gravity is then four-dimensional at short distances and becomes weaker at larger distances.

Bent-core nematic liquid crystals: Opportunities and mysteries – Jim Gleeson Thu. February 26th, 2009
4:15 pm-5:15 pm

In this talk, we review recent progress with a new class of liquid crystalline materials. These materials, which are based upon molecules having a reduced symmetry class, exhibit unexpected behavior, both quantitatively and qualitatively. Furthermore, they also hold significant promise for novel technological applications. Experimental probes include high resolution calorimetry, mechano-electrical response, the effects of ultra-high magnetic fields and nonlinear optical properties. We will discuss various mechanisms which can potentially explain these effect.

Testing global isotropy and some interesting cosmological models with CMB – Amir Hajian Tue. February 24th, 2009
11:30 am-12:30 pm

Simplest models of the Universe predict global (statistical) isotropy on large scales in the observable Universe. However there are a number of interesting models that predict existence of preferred directions. In this talk I will present results of using CMB anisotropy maps to test the global isotropy of the Universe on its largest scales, and will show how that can help us constrain interesting models such as topology of the Universe and anisotropic cosmological models (e.g. Bianchi models). I will also discuss the intriguing lack of power on large angular scales in the observed CMB maps and implications that it may have for cosmology.

Dipole in a Magnetic Field, Work, and Quantum Spin – Robert Deissler Mon. February 23rd, 2009
12:30 pm-1:30 pm

Place an atom in a nonuniform static external magnetic field and, because of the interaction between the atom’s magnetic moment and the magnetic field gradient, the atom will accelerate. This, of course, is what occurs in the classic Stern-Gerlach experiment. An important and fundamental question, which has been neglected in the literature, is whether or not the magnetic field is doing work on the atom. It is shown that, while the magnetic field does no work on the electron orbital contribution to the magnetic moment (the source of translational kinetic energy being the atom’s internal energy), whether or not it does work on the electron-spin contribution to the magnetic moment depends on whether the electron has an intrinsic rotational kinetic energy associated with its spin.

Hilltop Quintessence – Sourish Dutta Tue. February 17th, 2009
11:30 am-12:30 pm

We examine hilltop quintessence models, in which the scalar field is rolling near a local maximum in the potential, and w is close to -1. We first derive a general equation for the evolution of the scalar field in the limit where w is close to -1. We solve this equation for the case of hilltop quintessence to derive w as a function of the scale factor; these solutions depend on the curvature of the potential near its maximum. Our general result is in excellent agreement (delta w < 0.5%) with all of the particular cases examined. It works particularly well (delta w <

Synthesis of Novel Fuel Cell Membranes with Aligned Proton Conducting Pathways – Matt Yates Mon. February 16th, 2009
12:30 pm-1:30 pm

Novel approaches have been developed to engineer the microstructure of proton conducting membranes to enhance proton transport. Polymer composite and ceramic membranes were synthesized in which proton conducting pathways are aligned through the plane of the membrane. For polymer composite membranes, electric fields are applied during membrane synthesis to cause proton conducting domains aggregate into connected chains aligned through the membrane. For ceramic membranes, surfactant mediated crystallization is employed to direct crystal growth, resulting in aligned proton conducting paths. For both types of membranes, the engineered microstructure results in significantly enhanced proton conductivity through the membranes and improved performance of the membranes in fuel cells.

Atomic-Scale Spectroscopy of Single-Molecule Junctions – Georgy Nazin Thu. February 12th, 2009
4:15 pm-5:15 pm

Molecular junctions have attracted a great deal of attention recently due to their importance in the new field of Molecular Electronics. Electron transport in such junctions is a result of a complex interplay of many factors, including molecular electronic structure, adsorption configuration, and chemical environment.

Scanning Tunneling Microscopy (STM) is a powerful approach to molecular junction characterization because of its ability to provide atomic-level detail about the electronic structures and morphologies of these junctions. By using this approach, we investigated for the first time, a number of fundamental properties of molecular junctions:

1) By measuring the current-voltage characteristics of individual molecules,

Structure and dynamics of non-equilibrium colloidal suspensions – Jacinta Conrad Mon. February 9th, 2009
4:15 pm-5:15 pm

Colloidal suspensions are ubiquitous in industrial and technological applications; moreover, the precise control over the interparticle interactions allows such suspensions to serve as excellent model systems for a variety of complex fluids and soft materials. In addition, the large size of colloidal particles enables direct visualization of local structure. In this colloquium I will discuss two studies relating the structure of non-equilibrium colloidal suspensions to their flow properties. First, we use confocal microscopy to investigate relationships between structure and dynamics near the hard-sphere colloidal glass transition, one of the fundamental unsolved problems in condensed matter physics. By identifying slowly-relaxing regions within our samples,

Molecular materials for dynamic holography and lasing applications – Jarek Mysliewiec Wed. February 4th, 2009
12:30 pm-1:30 pm

The subject of the presentation will be focused on molecular materials like liquid crystals, photochromic polymers or modified DNA-dye systems and their possible applications for lasing and dynamic optical information recording. Results on optical information processing were obtained in a typical degenerate two- or four-wave mixing experiments. For amplified spontaneous emission measurements, nano- or picosecond lasers of different wavelengths (355 nm and 532 nm) were used.

Can the WMAP Haze really be a signature of annihilating neutralino dark matter? – Daniel Cumberbatch Tue. February 3rd, 2009
11:30 am-12:30 pm

Observations by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite have identified an excess of microwave emission from the centre of the Milky Way. It has been suggested that this {\it WMAP haze} emission could potentially be synchrotron emission from relativistic electrons and positrons produced in the annihilations of one (or more) species of dark matter particles. In this paper we re-calculate the intensity and morphology of the WMAP haze using a multi-linear regression involving full-sky templates of the dominant forms of galactic foreground emission, using two different CMB sky signal estimators. The first estimator is a posterior mean CMB map,

Surfaces and Interfaces in Nanoscale Electronic Materials: from Understanding to Engineering – Pengpeng Zhang Mon. February 2nd, 2009
4:15 pm-5:15 pm

Surfaces and interfaces play a critical role in determining properties and functions of nanomaterials, in many cases simply dominating bulk properties, owing to the large surface- and interface-to-volume ratio. One can further engineer and improve the performance of nanoscale devices through the control of surface and interface chemistry. Using Si nanomembranes as a model system, we have investigated how surfaces and interfaces influence electrical transport properties at the nanoscale by means of scanning tunneling microscopy (STM) and four-probe measurements. We show that electronic conduction in Si nanomembranes is not determined by bulk dopants but by the interplay of surface and interface electronic structures with the “bulk”

The 2008 Science Nobel Prizes – what were they given for? – Tanmay Vachaspati, Jonathan Karn, Piet de Boer Thu. January 29th, 2009
4:15 pm-5:15 pm

In this mini-symposium, Tanmay Vachaspati from Physics, and Jonathan Karn and Piet de Boer, from Molecular Biology and Microbiology, will describe the work for which the 2008 Nobel Prizes in Physics, Physiology and Medicine, and Chemistry, respectively, were awarded.

Multi-brane Inflation in String Theory – Amjad Ashoorioon Tue. January 27th, 2009
11:30 am-12:30 pm

I will talk about two inflationary scenarios in which the cooperative behavior of multiple branes give rise to inflation. In the first one, which we call cascade inflation, assisted inflation is realized in heterotic M-theory and by non-perturbative interactions of N M5-branes. The features in the inflaton potential are generated whenever two M5-branes collide with the boundaries. The derived small-scale power suppression could serves as a possible explanation for the dearth of observed dwarf galaxies in the Milky Way halo. In the second one, the transverse dimension of coincident D3-branes, which are N-dimensional matrices, result in inflation. We discuss how various scenarios such as chaotic,

High temperature superfluidity in high energy heavy ion collisions at RHIC and forward physics with TOTEM at LHC – Tamas Csorgo Tue. January 13th, 2009
11:30 am-12:30 pm

Five important milestones have been achieved in high energy heavy ion collisions utilitizing the Relativistic Heavy Ion Collider at BNL: – a new phenomena – which was proven to signal a new state of matter – this state of matter was found to be a perfect fluid, with temperatures reaching 2 terakelvins and more – the degrees of freedom were shown to be the quarks – and the kinematic viscosity of this matter at extemely high temperatures were found to be less than that of a superfluid 4He at the onset of superfluidity. I will summarize these milestones and some more recent novel results of the RHIC programme and also outline an interesting new direction,

How Do Physics and Nanotechnology Advance the Research on Renewable Energy? – Zhifeng Ren Tue. January 13th, 2009
4:15 pm-5:15 pm

Physics played an extremely important role in the electronics technology. Now nanotechnology is playing a leading role in the future technologies as important as physics did. Understanding the physics at the nanoscale is essential to the advancement and commercialization of any nanotechnology that is being studied. As two examples, I will talk about how the understanding of physics and nanotechnology will help to improve the solar energy conversion efficiency using photovoltaic and thermoelectric materials. With the potential of both technologies fully realized, we will have a transformative change in energy harvesting and conversion, which will certainly help reduce the dependence of oil,

Electronics Based on Crystalline Organic Semiconductors – Art Ramirez Thu. January 8th, 2009
4:15 pm-5:15 pm

Organic semiconductors are widely discussed for applications requiring large area and low processing cost. Thin film organics are already used in applications not requiring high speed or efficiency, such as display LEDs. To understand the materials limits of such semiconductors we study fundamental transport processes in devices made from single crystals of small molecules such as pentacene and rubrene. Photoluminescence, FET transconductance, and gate modulated activation energy spectroscopy (GAMEaS) allow the identification of oxygen as the dopant in rubrene. Using these techniques, we demonstrate for the first time, controllable doping in an organic semiconductor. I will discuss the implications of this work for solar energy.

Seeing and Moving Magnetic Nanoparticles – Sara Majetich Tue. January 6th, 2009
3:30 pm-4:30 pm

Monodomain magnetic nanoparticles act in many ways like giant spins. They differ from bulk magnets because they can move, and they differ from atomic magnetic moments because they can be imaged and tracked individually. These particles are an excellent model system for investigations of phase transitions on the nanoscale, and in addition they are relevant to magnetic recording media and applications in biomedicine. Following a brief introduction to the physics of magnetic nanoparticles, examples from each of these areas will be described.

For nanoscale magnetic imaging, monodisperse, surfactant-coated nanoparticles are first self-assembled into ordered monolayer arrays using Langmuir layer techniques.

Magnetism in Reduced Dimensions: Exchange Bias (2D) and Myoglobin-based Single-Electron Transistors (0D) – D. Lederman Thu. December 18th, 2008
4:15 pm-5:15 pm

In this talk I will outline two major efforts in my lab relating to magnetism: exchange bias, a subject that has occupied me for the past fifteen years, and protein-based single-electron transistors, which my group has studied during the past three years.

Exchange bias is the interaction at the interface between an antiferromagnetic material and a ferromagnetic thin film or nanoparticle which causes the center of the ferromagnetic hysteresis loop to shift away from zero field, effectively resulting in a unidirectional anisotropy. Despite the fact that this effect was discovered approximately fifty years ago, and that it is used in magnetic sensors found in hard drives,

Physics of Self-Assembly of Nanoporous Particles: What Defines Their Shape – Igor Sokolov Mon. December 8th, 2008
4:15 pm-5:15 pm

Growth of even simple crystals is a rather hard problem to describe because of the non-equilibrium, kinetic nature of the process. Recently a synthesis of extraordinary curved nanoporous silica colloidal shapes, such as rods, discoids, spheres, tubes and hollow helicoids has been reported. These particles demonstrate an example of shapes of high complexity, similar to one observed in the biological world. Furthermore, these structures are the natural examples of the assembly of nanostructures into larger scale objects, which is one of the most important tasks of modern nanotechnology. In this respect, the ability to control curved shapes portends a variety of applications and new technologies where nanostructure and geometry determine function (for example,

Shining (some) light on dark matter – Daniel Boyanovsky Thu. December 4th, 2008
4:15 pm-5:15 pm

Most of the matter in the Universe is dark, and is supposed to be SOME particle that interacts very weakly with other particles and has not YET been found. I will summarize the observational evidence for dark matter and offer a pedagogical description of gravitational collapse, galaxy formation, and the microphysics of dark matter, describing the difference between cold, hot and warm dark matter candidates.

I will describe the results of large scale numerical simulations and observational discrepancies in satellite galaxies and how these provide constraints on the microphysics of dark matter. Finally I will mention some potential DM candidates (cold,

Bent-core nematic liquid crystals: Opportunities and mysteries – Jim Gleeson Mon. December 1st, 2008
12:30 pm-1:30 pm
Anthropy and entropy – Irit Maor Tue. November 25th, 2008
11:30 am-12:30 pm

TBA

Phonon expansion and dispersion: Condensed matter channels: Material diagnosis – Dov Hazony Mon. November 24th, 2008
12:30 pm-1:30 pm

Propagating basic acoustic pulses may behave as phonons. They can be characterized and utilized to evaluate channels through which they have travelled.

First Principles Methods for the Design of Materials [joint with Chemistry] – Gerbrand Ceder Thu. November 20th, 2008
4:30 pm-5:30 pm

First principles methods can now be used to predict many properties of materials. Even crystal structure and surface chemistry, long elusive to computational modeling, can now be predicted with novel methods. I will show applications for materials in electrocatalysts and rechargeable batteries.

On the Challenge to Unveil the Microscopic Nature of Dark Matter – Scott Watson Tue. November 18th, 2008
11:30 am-12:30 pm

Despite the successes of modern precision cosmology to measure the macroscopic properties of dark matter, its microscopic nature still remains elusive. LHC is expected to probe energies relevant for testing theories of electroweak symmetry breaking, and as a result may allow us to produce dark matter for the first time. Other indirect experiments, such as PAMELA, offer additional ways to probe the microscopic nature of dark matter through observations of cosmic rays. Results from a number of indirect detection experiments seem to suggest that our old views of the creation of dark matter may need revisited. This is also suggested by theories of electroweak symmetry breaking that are required to be well behaved at high energies and in the presence of gravity.

Terahertz Time-Domain Measurement of Ballistic Electron Resonance in a Single-walled Carbon Nanotube – Zhaohui Zhong Mon. November 17th, 2008
12:30 pm-1:30 pm

The terahertz (~ 100 GHz to 10 THz) electrical properties of nanomaterials are of relevance both to the fundamental science of low-dimensional systems and to the operation of next-generation smaller and faster electronics. I will describe the first terahertz time-domain electrical measurements of single-walled carbon nanotube transistors. A ballistic electron resonance is directly observed with a picosecond-scale period corresponding to the roundtrip transit of an electron along the nanotube. The electron velocity is found to be constant and equal to the Fermi velocity, showing that the high-frequency electron response is dominated by single-particle excitations rather than collective plasmon modes. These results demonstrate a powerful new tool for directly probing picosecond electron motion in nanostructures.

The Glass Transition and its Relevance for Biological Systems – Alexei Sokolov Thu. November 13th, 2008
4:15 pm-5:15 pm

For thousands of years people have been using glass transition processes and glasses in their everyday life. For hundreds of years researchers have been studying the glass transition phenomenon. However, understanding the microscopic mechanism underlying the tremendous slowing down of structural relaxation remains one of the main challenges in current condensed matter physics.

This talk will present an overview of new ideas and experimental results formulated and obtained during the last two decades. It appears that the glass transition on a molecular level actually occurs at temperatures much above the conventional glass transition temperature. Understanding of this important point shifted significantly the focus of current research and resulted in deeper microscopic understanding of the glass transition.

Room temperature ferromagnetism in semiconducting oxides – Chandran Sudakar Mon. November 10th, 2008
12:30 pm-1:30 pm

Diluted magnetic semiconductors are formed when magnetic transition metal ions are doped in small concentrations into a semiconductor host lattice. The first reports of ferromagnetism being observed at room temperature in a dilutely doped semiconducting oxide film attracted a great deal of attention, but were also met with considerable skepticism. These materials would have enormous potential for developing new classes of electronic devices, but there were concerns that the observed magnetism arose from impurity contributions, rather than any intrinsic property of the material. Although there has been some progress made in understanding these systems, in particular, the important role played by oxygen vacancies,

Genesis: The Scientific Quest for Life’s Origins – Robert Hazen Thu. November 6th, 2008
4:30 pm-5:30 pm

Professor Robert Hazen is a respected and widely published geochemist who studies chemical evolution and the origin of life and has a mineral “hazenite” named after him.

Spin injection, transport, and control in Silicon – Ian Appelbaum Mon. November 3rd, 2008
12:30 pm-1:30 pm

The intrinsic angular momentum of an electron (spin) – and its associated magnetic moment – can encode information: spin “up” or “down” can be interpreted as “0” or “1”, and potentially be used as the physical realization of a new paradigm of computing beyond electronics. However, this concept of spin-electronics (“spintronics”) needs to be built using a material where the electron spin orientation is preserved over long times (to enable many gate operations) and long distances (so that many devices can be integrated). Silicon, the materials basis for electronics, has been known for decades to have an extraordinarily long spin lifetime,

Physics and Baseball: An Intersection of Passions – Alan M. Nathan Thu. October 30th, 2008
4:15 pm-5:15 pm

I have been a physicist for all my professional life. I have been a baseball fan even longer. And in recent years, I have figured out that I can do both physics and baseball at the same time. It is the ultimate in having your cake and eating it too.

In this talk, I will discuss some of the ways that a physicist analyzes the game of baseball. In the course of doing so, I will address some interesting and practical questions from a physics perspective, such as: How does a baseball bat work? Why do aluminum bats outperform wood bats?

Coupling nanomechanical motion to electromagnetic fields through the Casimir effect and surface evanescent waves – HoBun Chan Fri. October 24th, 2008
12:30 pm-1:30 pm

The miniaturization of mechanical devices opens new opportunities for investigating and exploiting novel phenomena that occur for components in close proximity. The Casimir force, for example, originates from the zero-point quantum fluctuations of the electromagnetic fields. I will describe experiments that investigate the Casimir effect in micromechanical devices. In particular, we demonstrate the strong boundary dependence of the Casimir force on silicon surfaces with an array of nanoscale trenches. In another effort, subwavelength structures are fabricated on the surface of metal films to strongly modify their interaction with light. The evanescent fields channel the optical energy to specific locations, resulting in strong and localized field enhancement.

South Pole Telescope: From conception to first discovery – Zak Staniszewski Tue. October 21st, 2008
11:30 am-12:30 pm

The South Pole Telescope recently discovered three new galaxy clusters in their CMB maps via the Sunyaev Zel’dovich (SZ) effect (Staniszewski et al. 2008). These are the first galaxy clusters discovered using this promising new technique. The number of galaxy clusters at a given redshift depends strongly on the expansion history of the universe as well as the relative abundances of matter, dark matter and dark energy during structure formation. The brightness of the SZ signal from a galaxy cluster is nearly redshift independent, making it a powerful tool for discovering galaxy clusters that were forming when dark energy was becoming important.

Charge Transport Phenomena in MilliKelvin Germanium and Detectors of the Cryogenic Dark Matter Search – Kyle Sundqvist Mon. October 20th, 2008
12:30 pm-1:30 pm

The Cryogenic Dark Matter Search (CDMS) seeks to detect putative weakly-interacting massive particles (WIMPS), which could explain the dark matter problem in cosmology and particle physics. By simultaneously measuring the number of charge carriers and the energy in non-thermalized phonons created by particle interactions in intrinsic Ge and Si crystals at a temperature of 40 mK, a signature response for each event is produced. This response, combined with phonon pulse-shape information, allows CDMS to actively discriminate candidate WIMP interactions with nuclei apart from electromagnetic radioactive background which interacts with electrons. The challenges associated with these techniques are unique. Carrier drift-fields are maintained at only a few V/cm,

Primordial Nongaussianity and Large-Scale Structure – Dragan Huterer Fri. October 17th, 2008
11:30 am-12:30 pm

The near-absence of primordial nongaussianity is one of the basic predictions of slow roll, single-field inflation, making measurements of nongaussianity fundamental tests of the physics of the early universe. I first review parametrizations of nongaussianity and briefly review the history of its measurements from the CMB and large-scale structure. I then present results from recent work where effects of primordial nongaussianity on the distribution of largest virialized objects was studied numerically and analytically. We found that the bias of dark matter halos takes strong scale dependence in nongaussian cosmological models. Therefore, measurements of scale dependence of the bias, using various tracers of large-scale structure,

Complex Interstellar Molecules [joint colloquium with Astronomy] – Eric Herbst Thu. October 16th, 2008
4:15 pm-5:15 pm

In the last thirty years, astronomers have detected a large number of molecules in the gas and solid phases of interstellar clouds, which are large and inhomogeneous accumulations of matter in between stars in our galaxy and others. The molecules are useful as probes of the current physical conditions in interstellar clouds and also yield information on the cloud lifetimes. The most complex of these molecules are found in regions of interstellar clouds that are collapsing to form stars and planets, and so tell us about the evolutionary stages leading to stellar and planetary formation. Moreover, these complex molecules are of interest to chemists because of the unusual manner in which they are synthesized and to geologists and biologists because they are related to the initial inventory of molecules present at the creation of planets.

In Search of the Coolest White Dwarfs – Evalyn I.Gates Tue. October 14th, 2008
11:30 am-12:30 pm

Cool white dwarf stars are among the oldest objects in the Galaxy. These relics of an ancient stellar population offer a window into the early stages of the galaxy and its formation, and more data on the oldest and coolest white dwarfs may help resolve the interpretation of microlensing searches for MACHOs in the galactic halo. The Sloan Digital Sky Survey (SDSS) and the SEGUE program of SDSS-II are ideally suited to a search for these rare objects, and to date we have discovered 13 new ultracool white dwarfs =96 those with temperatures below 4000K =96 constituting the majority of these faint stellar fossils.

Human Detectors: A Scientific Approach to Increasing the Number of Women in Science – Evalyn Gates Mon. October 13th, 2008
4:15 pm-5:15 pm

What do the search for the mysterious dark matter that pervades the Universe, and the search to understand the underrepresentation of women in university physical science departments have in common? Both challenges require a lot of hard work and a clear understanding of the problem – including a careful analysis of the detectors we use and the unavoidable backgrounds that affect our results. We need to approach the question of women in math and science with the same enthusiasm and skill that we bring to our explorations of the cosmos – and start thinking more like scientists.

This colloquium has been made possible with support from th