Shopping cart

close

Upcoming Events

Event Date and Location Summary
Evelyn Hu (Harvard University) Thu. January 24th, 2019
4:00 pm-4:00 pm
at Rockefeller 301

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

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,

Geoffrey Landis (NASA, Glenn) Thu. February 7th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
Geoffrey Landis (NASA Glenn) Thu. February 7th, 2019
4:00 pm-5:00 pm
at Rockefeller 301

TBA

Ken Singer (CWRU Physics) Thu. February 14th, 2019
4:00 pm-5:00 pm
at Rockefeller 301

TBA

Raman Sundrum (University of Maryland) Thu. February 21st, 2019
4:00 pm-5:00 pm
at Rockefeller 301
Michelle Soares-Santos (Brandeis University) Thu. February 28th, 2019
4:00 pm-5:00 pm
at Rockefeller 301

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.

No Colloquium. APS March Meeting. Thu. March 7th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
No Colloquium. Spring Break. Thu. March 14th, 2019
1:00 am-1:00 am
at Rockefeller 301
Subir Sachdev (Harvard University) Thu. March 21st, 2019
4:00 pm-5:00 pm
at Rockefeller 301
Ira Rothstein (Carnegie Mellon University) Thu. March 28th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
Matthew Fisher (KITP Santa Barbara) Thu. April 4th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
Allan MacDonald (U Texas Austin) Thu. April 18th, 2019
4:00 pm-5:00 pm
at Rockefeller 301

Moiré pattern physics  in two-dimensional materials

Sinead Griffin (Lawrence Berkeley Lab) Thu. April 25th, 2019
4:00 pm-5:00 pm
at Rockefeller 301
Bharat Ratra (University of Kansas) Thu. September 5th, 2019
4:00 pm-5:00 pm
at Rockefeller 301

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.

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.

Mark Griswold (CWRU Radiology) Thu. November 29th, 2018
4:00 pm-5:00 pm
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,

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,

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]. 

 

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.

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.

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.

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,
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.
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 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.

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,
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.
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.

TBA Thu. March 29th, 2018
4:00 pm-5:00 pm
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,

Spring Break Thu. March 15th, 2018
4:00 pm-5:00 pm
APS March Meeting Thu. March 8th, 2018
4:00 pm-5:00 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.

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,

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.

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 (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.

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.

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,

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.

No colloquium this week Thu. October 12th, 2017
4:00 pm-5:00 pm
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,

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.

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,

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,

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. 

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,
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,

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,
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.

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,

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,

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.  

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.

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.

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. 
Thu. February 16th, 2017
4:00 pm-5:00 pm
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;
Thu. February 2nd, 2017
4:00 pm-5:00 pm
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,

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? 

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.

Mike Hinczewski (CWRU Physics) Thu. December 1st, 2016
4:00 pm-5:00 pm
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,

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.

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,
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,
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.

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,

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,

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.

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).

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.

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,

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.
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.

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,

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,

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.

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.

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.

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
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.

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.

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.

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.

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.

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.

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.

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.

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?

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.

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
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.

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.

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,

Interacting particle models and phase transitions for social particles – Alethea Barbaro Thu. March 19th, 2015
4:15 pm-5:15 pm
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.

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?

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,

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”.

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?

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.

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,

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.

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.

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.

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,

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,

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.

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.

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.

Results from the LUX dark matter search, and prospects for the future – Tom Shutt Thu. April 3rd, 2014
4:15 pm-5:15 pm
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,

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 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?

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

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,

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.

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.

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.

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.

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.

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,

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,

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.

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.

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.

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.

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.

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.

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.

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,

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.

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.

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.

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.

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.

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.

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.

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.

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,

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.

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.

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.

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.

“How we fixed the Hubble Space Telescope” – James Breckinridge Thu. September 27th, 2012
4:15 pm-5:15 pm
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’

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!

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,

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.

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].

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.

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),

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,

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,

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.

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.

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,

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,

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.

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.

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.

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.

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.

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,

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.

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”

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.

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.

“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.

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;

Financial Mathematics for Physicists – Bryan Lynn Thu. April 14th, 2011
4:15 pm-5:15 pm
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.

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,

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.

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,

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.

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,

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.

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.

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.

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.

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,

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”,

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,

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.

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

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.

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.

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.

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.

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.

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,

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,

Deterministic Isoeffective Dose – Proposal for a New Unit – The Barendsen (Bd) – Barry Wessels, Thu. April 8th, 2010
4:15 pm-5:15 pm
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.

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.

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,

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,

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.

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,

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).

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.

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.

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?

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?”

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.

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,

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,

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.

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.

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.

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,

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.

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.

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.

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.

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.

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.

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.

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.

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,

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.

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,

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.

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.

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.

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?

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.

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 the Krumhansl Foundation through the Case Alumni Association

Designing Self-Propelled Polymeric Capsules and Gels – Anna Balazs Thu. October 9th, 2008
4:15 pm-5:15 pm

Using simulation and theory, we demonstrate how nanoparticles can be harnessed to regulate the interaction between two initially stationary microcapsules on a surface and promote the self-propelled motion of these capsules along the substrate. The first microcapsule, the “signaling” capsule, encases nanoparticles, which diffuse from the interior of this carrier and into the surrounding solution; the second capsule is the “target” capsule, which is initially devoid of particles. Nanoparticles released from the signaling capsule modify the underlying substrate, and thereby initiate the motion of the target capsule. The latter motion activates hydrodynamic interactions, which trigger the signaling capsule to follow the target.

Survival of Cooper pairs in the insulating phase: “super-insulators” – Sambandamurthy Ganapathy Thu. October 2nd, 2008
4:15 pm-5:15 pm

I will present experimental results from our study of 2D thin films that are driven through the superconductor-insulator quantum phase transition. In particular, the microscopic transport behavior of the films at high magnetic fields will be presented. The films show novel collective behavior in the insulating phase that suggests the survival of superconducting correlations well above the critical point of the quantum phase transition, thus forming a super-insulator.

Darwin Celebration Lecture – Judge John E. Jones III Thu. September 25th, 2008
5:00 pm-6:00 pm
CWRU Theory Passes Fermilab Test 30 Years Later – Robert W. Brown Thu. September 18th, 2008
4:15 pm-5:15 pm

The standard model had become everyone’s favorite as the fundamental theory of the world by the mid-1970’s. So, even before the bosonic carriers of the weak force (the W+, W-, and Z0) were officially discovered, our CWRU theory group had proposed proton-collider experimental tests of whether the weak bosons would show that they had the interaction couplings predicted by the standard model. In calculating predictions for the tests, an unexpected feature was found. Three generations of experimental searches looked for this feature, getting nowhere in the 80’s and 90’s, but finally, in 2008, the elusive feature was found. It connects short-distance particle physics to classical radiation patterns that can be found,

Critical Dipoles and Singular Potentials – David Griffiths Thu. September 11th, 2008
4:15 pm-5:15 pm

The Schrodinger equation for a point charge in the field of a stationary electric dipole admits bound states when the dipole moment exceeds a certain critical value. It is not hard to see why this might be the case, but it is surprisingly difficult to calculate the critical dipole moment. One method exploits a connection between this problem and the infamous 1/x-squared potential on the half-line, an intriguing system that confounds all our quantum intuitions. Resolving its paradoxes requires sophisticated theoretical machinery: renormalization, anomalies, and self-adjoint extensions.

The Search for Special Nuclear Material Using Particle Physics Techniques – David Koltick Thu. September 4th, 2008
4:15 pm-5:15 pm

One of the most devastating attacks a terrorist group could mount would be to detonate an atomic bomb in a city. If exploded in Manhattan during working hours, for example, a bomb with a yield of only 1 kiloton could kill 200,000 people outright and flatten eleven city blocks. In theory, as little as 4 kilograms (9 pounds) of plutonium would be needed to make a bomb. As little as 16 to 20 kilograms of highly enriched uranium would be needed to make an efficient bomb; a crude bomb could be made with 50 to 100 kilograms of uranium. By contrast,

[Entrepreneuship colloquium] The Possibilities Toolbox: Surprising Revelations – Kimberly Wiefling Tue. August 26th, 2008
4:15 pm-5:15 pm

In “The User Illusion” Tor Norretranders notes that there is a significant gulf between perception and reality. Consciousness has a bandwidth. We routinely ignore most of the information entering our senses, information that doesn’t fit our worldview. In this colloquium/workshop, whose full title is “The Possibilities Toolbox: Surprising Revelations About the Nature of Reality and How to Shape It”, we will examine the idea that “being sure” is not the same as “being right” and explore ways to expand possibilities. Also, pursuing possibilities sometimes requires that we fly in the face of conventional wisdom and challenge the CAVE people (Citizens Against Virtually Everything).

Precision cosmology for the 21st century – Roberto Trotta Wed. May 7th, 2008
4:15 pm-5:15 pm

The detailed study of cosmic microwave background anisotropies has contributed to transform cosmology into a quantitative, data driven field. Techniques such as weak gravitational lensing and baryonic acoustic oscillations have the potential to become new powerhouses of precision cosmology over the next decade, taking cosmology into a new era of exciting discoveries.
In this talk I will review recent developments towards the achievement of precision cosmology and present the current cosmological concordance model. I will discuss outstanding challenges and future avenues of investigation, and I will survey the evolution of the field in the next 25 years.

Astronomy with Radioactivities [joint colloquium with Astronomy] – Dieter Hartmann Thu. April 24th, 2008
4:15 pm-5:15 pm

The production and distribution of new isotopes is a key topic of the astrophysical theme of chemical evolution. We distinguish Galactic Chemical Evolution (GCE), which is concerned with abundances in stars and the Interstellar Medium (ISM), and Cosmic Chemical Evolution (CCE), which extends this research to galaxies, clusters of galaxies, and the Intergalactic Medium (IGM). The ultimate goal is to understand the origin and evolution of all known nuclei, their abundances in various environments, ranging from planetary- to stellar systems. The cosmic cycle is driven by the formation, evolution, and deaths of stars. Strong winds and explosive final stages of massive stars determine the chemical,

A Neutron Electric Dipole Moment? – Brad Filippone Thu. April 17th, 2008
4:15 pm-5:15 pm

For more than fifty years physicists have searched for a neutron Electric Dipole Moment (EDM) beginning with a search for Parity violation by Purcell and Ramsey. Today the search is motivated by a possible “large” violation of Charge-Parity (CP) symmetry which is suggested by the observation of substantially more matter than antimatter in the Universe. A new experiment is underway to search for a neutron EDM with the goal of improving the sensitivity by more than two orders-of-magnitude. This ambitious experiment brings together physicists with expertise in particle, nuclear, atomic and low-temperature physics. We will discuss the importance of searching for new sources of CP violation as well as the technical challenges involved in this new experiment.

Wrinkling, Folding and Crumpling of Thin Sheets – Narayanan Menon Thu. April 10th, 2008
4:15 pm-5:15 pm

Under the action of external forces, thin sheets tend to bend out of plane rather than stretch. For weak forcing, this leads to the distinctive wrinkling instabilities that you see on your skin. When more strongly confined, sheets crumple, and condense stress into a network of ridges which confer rigidity on the bulk material. At even stronger forcing, ridges develop into plastic creases which lead to complex time-dependent mechanical properties. I will describe experiments that study various aspects of this progression of features, concentrating on the wrinkling patterns seen in ultra-thin polymeric sheets.

Rydberg Electron Wave Packets: Observing and Manipulating Electrons within an Atom – Carlos Stroud Thu. April 3rd, 2008
4:15 pm-5:15 pm

We will review a series of calculations and experiments that my research group has carried out over the past few years in which we have used picosecond and femtosecond laser pulses to image and manipulate electrons within an atom. The electrons can be excited into localized wave packets moving in orbits almost a micrometer in diameter. They approach the classical limit of a single atom. The electrons can also be manipulated into very complex shapes in which we are literally sculpting the or writing information upon it. The electrons can also be entangled and used for quantum information storage and processing.

The Quantum Mechanics of Global Warming – Brad Marston Thu. March 20th, 2008
4:15 pm-5:15 pm

Quantum mechanics plays a crucial, albeit often overlooked, role in our understanding of the Earth’s climate. In this talk three well known aspects of quantum mechanics are invoked to present a simple physical picture of what may happen as the concentrations of greenhouse gases such as carbon dioxide continue to increase.

Historical and paleoclimatic records are interpreted with some basic astronomy, fluid mechanics, and the use of fundamental laws of physics such as the conservation of angular momentum. I conclude by discussing some possible ways that theoretical physics might be able to contribute to a deeper understanding of climate change.

Thermodynamics of carrier-mediated magnetism in semiconductors – A. G. Petukhov Thu. March 6th, 2008
4:15 pm-5:15 pm

We propose a model of carrier-mediated ferromagnetism in semiconductors that accounts for the temperature dependence of the carriers. The model permits analysis of the thermodynamic stability of competing magnetic states, opening the door to the construction of magnetic phase diagrams. As an example we analyze the stability of a possible reentrant ferromagnetic semiconductor, in which increasing temperature leads to an increased carrier density, such that the enhanced exchange coupling between magnetic impurities results in the onset of ferromagnetism as temperature is raised. We apply this approach to studying thermodynamic fluctuations of magnetization in small systems such as bound magnetic polarons and magnetic nano-islands.

Out of Darkness: The Quest for Lambda – Nemanja Kaloper Fri. February 29th, 2008
4:15 pm-5:15 pm

Recent astronomical observations are forcing us to face the cosmological constant problem, which is perhaps the greatest challenge of modern fundamental physics. Solving it seems to require a paradigm shift in our thinking about nature. In this talk I will explain why the physics of the cosmological constant is so elusive, discuss the ideas oft seen in connection to it, and specifically review why changing the gravitational sector of the theory may help.

Quasicrystals in Medieval Islamic Architecture – Peter J. Lu Thu. February 28th, 2008
4:15 pm-5:15 pm

The conventional view holds that girih (geometric star-and-polygon) patterns in medieval Islamic architecture were conceived by their designers as a network of zigzagging lines, and drafted directly with a straightedge and a compass. I discuss our recent findings that, by 1200 C.E., a conceptual breakthrough occurred in which girih patterns were reconceived as tessellations of a special set of equilateral polygons (girih tiles) decorated with lines. These girih tiles enabled the creation of increasingly complex periodic girih patterns, and by the 15th century, the tessellation approach was combined with self-similar transformations to construct nearly-perfect quasicrystalline patterns. Quasicrystal patterns have remarkable properties: they do not repeat periodically,

When Obsessions Collide: Golf and Physics – Robert Grober Thu. February 21st, 2008
4:15 pm-5:15 pm

The revolution in low power microelectronics has enabled the development of electronically enabled golf clubs, radically changing the relationship between the golfer and the golf club. These intelligent sensor systems provide quantitative measurements of the golf swing with unprecedented detail. Additionally, they have been implemented to enable real-time, audio biofeedback on the motion of the club. Transforming the golf swing into an audio sound-space provides a novel perspective of the golf swing and has yielded new insight into many aspects of the swing, tempo and timing in particular. This talk summarizes some of the interesting physics and biomechanics that have been learned about the golf swing through the use of this technology.

Beyond Concordance Cosmology – C. Contaldi Thu. February 14th, 2008
4:15 pm-5:15 pm

Cosmology has well and truly entered its ‘precision era’. The wealth of observations has led to ever tightening constraints on cosmological model parameters. Some of the most fundamental aspects of physics in the models however remain hidden behind the phenomenology of pseudo-parameters. Indeed many questions about how the early universe evolved remain unanswered. I will argue that, over the coming years, Cosmology will enter a ‘post-precision’ era where further observations will open a window onto the physics itself where many surprises may still be hiding.

Metallic Behavior and the Metal-Insulator Transition in Strongly Correlated 2D Holes – Xuan Gao Thu. February 7th, 2008
4:15 pm-5:15 pm

The celebrated scaling theory of localization asserted that all two- dimensional (2D) Fermionic systems are insulators. However, experiments in the 1990’s have revealed an intriguing metallic state and metal-insulator transition in various 2D semiconductor systems, where the carriers are strongly correlated. It is still being debated that if this 2D metallic state is a new electronic state of matter stabilized by strong Coulomb interactions. We have studied electrical transport properties of strongly interacting 2D holes in the world’s cleanest Gallium Arsenide quantum well samples down to ultra-low temperatures (T ~ 0.01K). We found that removing the spin degree of freedom (by applying a magnetic field parallel to the 2D plane) gradually drives the system back to the conventional ‘Fermi liquid’

Generalized Nematics: Hints for the GUTS / Electroweak Transition? – Rolfe Petschek Thu. January 31st, 2008
4:15 pm-5:15 pm

Nematics are materials that have only orientation order, usually described by a non-zero, uniaxial average for a traceless symmetric second rank tensor. I review our knowledge about orientational order involving a single traceless symmetric second rank tensor order parameter or a single vector order parameter. There is recent interest in systems with either higher rank tensor order parameters or additional important, possibly higher rank orientational order parameters. I will discuss theoretical results for such generalized nematics, including the rather striking differences between systems with single low rank tensor and single high rank tensor order parameters. Such differences, which seem to be generic to high-rank tensor order parameters in various symmetry groups,

Information Engines and the Second Law – Benjamin Schumacher Thu. January 24th, 2008
4:15 pm-5:15 pm

Maxwell’s demon, which extracts work from a thermodynamic system by acquiring information about it, has for more than a century been a favorite thought-experiment in the foundations of statistical physics. The demon has variously been viewed as a threat, an exception, an exemplar, and a means for extending the Second Law. I will describe a formulation of thermodynamics in which such “information engines” play the central role, yielding insights about entropy, information erasure, the meaning of temperature, and the connection between fluctuation and dissipation.

Magnetic exchange interactions – Walter Lambrecht Thu. January 17th, 2008
4:15 pm-5:15 pm

In this talk I will discuss the origins of magnetic exchange interactions in the underlying electronic structure from a first-principles point of view. I will start from the textbook examples of the Heisenberg Hamiltonian, the Stoner theory of itinerant magnetism and various indirect exchange couplings. I then pose the question of how these various behaviors should emerge naturally from a first-principles calculation of the electronic structure. I will present the disordered local moment picture that emerges from spin-density functional theory and how it is based on an adiabatic decoupling of slow and fast degrees of freedom. I will discuss how non-collinear magnetism and the linear response calculation of exchange interactions are naturally obtained in the framework of multiple scattering theories of electonic structure.

Computing the Cosmos: Illuminating the Dark Side with Clusters of Galaxies [joint colloquium with Astronomy] – Gus Evrard Thu. December 13th, 2007
4:15 pm-5:15 pm

Clusters of galaxies emerge at dense peaks in the vast cosmic web of large-scale structure that threads the universe. The non-linear dynamics governing their formation has been extensively studied using computational N-body and gas dynamical techniques, and many population properties are now well understood (or, at least, well calibrated) from this first-principles approach. The links between cosmological parameters and cluster population statistics are now strong enough to motivate large observational programs at optical, sub-mm and X-ray wavelengths. In this talk, I will review progress in modeling clusters as multi-component, gravitational systems and then address the role that cluster studies should play in illuminating dark sector physics over the coming decades.

From Jackson Homework to Quality Electrodynamics – Hiroyuki Fujita Thu. December 6th, 2007
4:15 pm-5:15 pm

Recent advances of magnetic resonance imaging (MRI) scanner design involve an ever-increasing number of receiver channels (32-128), which is required to realize the full potential of the so-called parallel imaging techniques that have been very rapidly developed over the last few years to improve the temporal and spatial resolution of MRI. In particular, 1.5-Tesla and 3-Tesla fast MRI clinical applications enabled by parallel imaging techniques are now realized and accepted as everyday routine clinical practices. At both of the field strengths, within the crucial constraints of maximum patient comfort and signal-to-noise ratio (SNR), the key requirement is an optimized multi-detector radiofrequency (RF) array coil leading to more advanced and faster clinical MR scans.

Breaking News from the Auger Observatory – Corbin Covault Thu. November 29th, 2007
4:15 pm-5:15 pm

The world’s largest cosmic ray observatory has recently reported a new result that represents a major step forward in our understanding of the origins of the highest energy cosmic rays. The astrophysical origins of the highest energy cosmic rays have remained a persistent mystery for decades. Where in the universe do these particles come from? How do they obtain such enormous energies? Now, we seem to be on the verge of getting a new handle on these questions. The Pierre Auger Observatory, in Malargue, Argentina, has been operating since 2004, and already we have some clues, including the energy spectrum and limits on photon flux that strongly suggest an extragalactic origin for the highest energy cosmic rays.

The Cosmic Microwave Background: Cosmology, Topology and Probability – Andrew Jaffe Thu. November 15th, 2007
4:15 pm-5:15 pm

The cosmic microwave background (CMB) gives us a glimpse of the Universe as it was only a few hundred thousand years old. The tiny fluctuations — one part in 100,000 — that we observe in the CMB trace out the fluctuations that would eventually become the galaxies and clusters that we see today. Our theories, on the other hand, predict only the statistical properties of those initial conditions. Measuring cosmological parameters therefore requires disentangling those statistical properties from our finite, noisy observations. Today, those observations (from instruments like the COBE and WMAP satellites) tell us that the universe is geometrically flat,

Thu. November 8th, 2007
4:15 pm-5:15 pm

For a price, it is possible to acquire unearned academic degrees from non-existent universities that market diplomas over the internet. The most sophisticated of these diploma mill cartels, based in Spokane, Washington, is now the subject of a multi-agency criminal investigation. It has used the turmoil in Western Africa to foster the illusion of recognition and accreditation by the Republic of Liberia. But these credentials were obtained through payments to government officials, and are no more legitimate than the supporting web of fake diplomatic missions, schools, accreditors, and credential evaluators created by the “Saint Regis” group. Their operation spans at least eighteen states and twenty-two countries,

Chromonic Liquid Crystals – Oleg Lavrentovich Thu. November 1st, 2007
4:15 pm-5:15 pm

Lyotropic chromonic liquid crystals (LCLCs) are formed by molecules with rigid polyaromatic cores and ionic groups at the periphery that form aggregates while in water [1]. Light scattering experiments demonstrate that the isotropic-to-nematic pretransitional behavior does not follow the classic Landau – de Gennes model, as the length of aggregates changes with temperature [2]. Most of the LCLCs are not toxic to the biological cells [3] and can be used as an amplifying medium in real-time biosensors [4]. The detector is based on the principle that the immune aggregates growing in the LCLC bulk trigger director distortions. Self-assembly of LCLC molecules into oriented structures allows one to use them in various structured films with potential applications as polarizers and optical compensators.

Fundamentals of Supernova Cosmology [joint with Astronomy] – Robert P. Kirshner Thu. October 18th, 2007
4:15 pm-5:15 pm

The use of thermonuclear supernova explosions as standard candles led to the discovery of cosmic acceleration and the search for the nature of dark energy. How good are these standard candles? How do we understand and model the variation in supernova properties? How does all of this fit in with what we know about stellar evolution and cosmic enrichment? I’ll describe what we know (and don’t know) about these questions and what is being done to answer them more securely in advance of a possible Joint Dark Energy Mission to measure the properties of dark energy.

Stabilizing Atmospheric CO_2 [joint colloquium with Chemistry] – Gregory H. Rau Thu. October 11th, 2007
4:30 pm-5:30 pm
Energy options [joint colloquium with Chemistry] – John Deutch Thu. October 4th, 2007
4:30 pm-5:30 pm
Science And Science Fiction – Robert Scherrer Thu. September 27th, 2007
4:15 pm-5:15 pm

I will explore the similarities and differences between the process of writing science fiction and the process of “producing” science, specifically theoretical physics. What are the ground rules for introducing unproven new ideas in science fiction, and how do they differ from the corresponding rules in physics? How predictive is science fiction? (For that matter, how predictive is theoretical physics?) I will also contrast the way in which information is presented in science fiction, as opposed to its presentation in scientific papers, and I will examine the relative importance of ideas (as opposed to the importance of the way in which these ideas are presented).

Real-time polarization spectroscopies: applications in thin film growth and photovoltaics – Robert Collins Thu. September 20th, 2007
4:15 pm-5:15 pm

Photovoltaics (PV) technologies based on thin films of hydrogenated amorphous silicon (a-Si:H) and polycrystalline cadmium telluride (pc-CdTe) have met with considerable success over the past few years. These thin film PV devices are deposited by chemical and physical vapor deposition methods on low cost substrates. Optimized devices have become increasingly complex, and in the case of a-Si:H technology include as many as a dozen major layers and several minor layers, as well, designed to capture a broad range of the solar spectrum. In addition, post-deposition processing may be required, and in the case of pc-CdTe this includes a critical anneal under CdCl2 vapor.

Energy Transport in One-dimensional Systems – Onuttom Narayan Thu. September 13th, 2007
4:15 pm-5:15 pm

In quasi one dimensional systems, the flow of energy has many unusual features. In the first part of this talk, I will show that the heat conductivity diverges in the thermodynamic limit in a large class of such systems. The form of the divergence is shown analytically to be universal. In the second part, I will discuss how disorder makes the flow of energy very slow and creates problems with equilibration. In the third part, I will present numerical results for the non-equilibrium flow of energy in disordered one dimensional systems, leading to an exact identity for wave propagation in nonlinear media.

The Physics Enterprise – C. Rosenblatt Thu. September 6th, 2007
4:15 pm-5:15 pm

A (mostly pictorial) history of how American physics evolved from Ben Franklin’s kite to the tens of billions of dollars spent annually in physics and physics-related research today.

Michelson Postdoctoral Prize lecture – Adam Bolton Wed. May 2nd, 2007
4:15 pm-5:15 pm
How to Efficiently Convert Electrical Energy into Light Using Organic Materials – Zakya H. Kafafi Thu. April 26th, 2007
4:15 pm-5:15 pm

How to Efficiently Convert Electrical Energy into Light Using Organic Materials

Low Temperature Physics and Physicists Six Decades Ago – B. S. Chandrasekhar Thu. April 19th, 2007
4:15 pm-5:15 pm

I shall describe what the field looked like when I entered it as a foot-soldier, i.e. research student, more than half a century ago: what was known, who knew it and looked for more, how they did it. I shall illustrate with examples from my experience and observation. To see where we were then is to realize how far we have come and how the community and its customs have changed.

An Explanation for Dayton Miller’s Anomalous “Ether Drift” Result – Tom Roberts Thu. April 12th, 2007
4:15 pm-5:15 pm

In 1933 Dayton Miller published the results of his voluminous observations using his ether drift interferometer, and proclaimed that he had determined the “absolute motion of the earth”. This result is in direct conflict with the prediction of Special Relativity, and also with numerous related experiments that found no such signal or “absolute motion”. I will present a complete explanation for his anomalous result by: a) showing that his results are not statistically significant, b) describing in detail how flaws in his analysis procedure produced a false signal with precisely the properties he expected, and c) presenting a quantitative model of his systematic drift that shows there is no real signal in his data.

Jamming – Andrea Liu Thu. April 5th, 2007
4:15 pm-5:15 pm

All around us things seem to get jammed. Before breakfast, coffee grounds and cereal jam as they refuse to flow into our filters and bowls. On the way to work, we are caught in traffic jams. In factories, powders jam as they clog in the conduits that were designed to have them flow smoothly from one side of the factory floor to the other. Our recourse in all these situations is to pound on our containers, dashboards and conduits until the jam miraculously disappears. We are usually so irritated by the jam that we do not notice that the approach to jamming and the jammed state,

Binary black holes and their echoes in the Universe – Pablo Laguna Thu. March 29th, 2007
4:15 pm-5:15 pm

A new window in astronomy will open once gravitational-wave interferometers detect “first light.” These detectors will give us a revolutionary view of the Universe, complementary to the electromagnetic perspective. The detection and characterization of gravitational waves is a formidable undertaking, requiring innovative engineering, powerful data analysis tools as well as careful theoretical and numerical modeling. Binary black holes are expected to be one of the primary sources of gravitational radiation. I will review the latest developments to numerically model binary black holes. I will also address the role that these simulations have of assisting us in exploring where and how gravitational wave observations can enhance our understanding of astronomical phenomena and gravity.

Plasmons in metallic nanostructures – Peter Nordlander Thu. March 22nd, 2007
4:15 pm-5:15 pm

The recent observation that certain metallic nanoparticles possess plasmon resonances that depend very sensitively on the shape of the nanostructure has led us to a fundamentally new understanding of the plasmon resonances supported by metals of various geometries. This picture- “plasmon hybridization”, reveals that the collective electronic resonances in metallic nanostructures are mesoscopic analogs of the wave functions of simple atoms and molecules, interacting in a manner that is analogous to hybridization in molecular orbital theory. The plasmon hybridization picture can be applied to an entire family of plasmonic nanostructures of various geometries, such as spherical shells, or ÒnanoshellsÓ, offset shells,

2007 Distinguished Lecture: Warped Passages: Unraveling the Mysteries of the Universe’s Hidden Dimensions Tue. March 20th, 2007
5:30 pm-6:30 pm
Self-assembled Molecular Nanostructures at Surfaces – Steven Tait Thu. March 1st, 2007
4:15 pm-5:15 pm

Producing nanometer-scale architectures on surfaces is a current technological and scientific challenge. A natural alternative to current fabrication methods is the self-assembly approach, which allows atomic and molecular building blocks to organize themselves into useful nanostructures and is a fundamental principle for growth in all living organisms. I will present our recent results of self-assembled supramolecular networks at surfaces, stabilized by non-covalent interactions. By selection of molecular building blocks with specific properties, we can “program” these systems to pattern a surface with homogenous networks of specific size, structure, and physical and chemical properties.

Controlled Fabrication and Imaging of Nano-Scale Devices – Douglas Strachan Thu. February 22nd, 2007
4:15 pm-5:15 pm

Molecular-scale devices hold the potential for a wide range of electronic applications requiring new fundamental scientific understanding.ÊOne of the biggest challenges in developing molecular-scale devices is to fabricate precisely and monitor the formation of the nanometer-scale electrodes.ÊWe have developed a technique that employs an applied current with feedback for controllably electromigrating a nano-scale electrode down to the quantum regime.ÊThe technique permits high-resolution imaging in a transmission electron microscope, which shouldhave far reaching applications in the design and study of these extremely small devices.

The Sensitivity Limits of Nanowire Bio-Sensors – Xuan Gao Wed. February 14th, 2007
4:15 pm-5:15 pm

Nanowire field effect transistors (NWFETs) are emerging as powerful sensors for bio-molecule detection. I will discuss the interplay of device parameters such as gate bias and NW diameter on the sensitivity of NWFET sensors. Based on a fundamental understanding of the device physics, we demonstrate greatly improved sensitivity in both pH and cancer marker protein detections by operating the NWFET in the subthreshold regime where carriers in nanowire have reduced screening ability.

Optoelectronic devices based on a semiconducting polymer homojunction – Janelle Leger Thu. February 8th, 2007
4:15 pm-5:15 pm

Junctions between p and n type semiconductors are the fundamental structure upon which nearly all semiconductor technology is based. The stabilization of such junctions within a solution-processed semiconductor has great potential in the continuing expansion of organic electronic and/or photonic devices. We describe a process for forming fixed polymer homojunctions that demonstrate stability and high rectification ratios. This method shows promise beyond light-emitting displays for a range of device architectures for rectification, amplification, and photovoltaic applications.

Colossal magnetoresistive manganites and high temperature superconductors: so different, yet so similar – Norman Mannella Thu. February 1st, 2007
4:15 pm-5:15 pm

Transition metal oxides constitute a prototype for complex electron systems in which electrons organize collectively and give raise to spectacular macroscopic properties, with the most prominent examples being high temperature superconductivity and colossal magnetoresistance. The study of these systems has to date unveil a common motif which is becoming a paradigm in condensed matter physics: the interplay and competition of multiple degrees of freedom like charge, lattice and spin.

In this talk, I will provide a compelling example of this paradigm by discussing the results of some recent angle-resolved photoemission spectroscopy (ARPES) investigations in the prototypical colossal magnetoresistive compound La1.2Sr1.8Mn2O7.

Bohr’s Vision, Delbruck’s Quest, and the Ironic Origins of Molecular Biology – Neil Greenspan Thu. January 18th, 2007
4:15 pm-5:15 pm

April 25th, 2003, marked the 50th anniversary of the publication, in Nature (171:737-738, 1953), of the paper by James D. Watson and Francis H. C. Crick describing the double-helical structure of DNA. While some would date the beginning of molecular biology to this paper, it is not difficult to find antecedent developments, experimental and conceptual, that point in the same direction. One such event that contributed to the origins of molecular biology is the lecture, “Light and Life,” delivered by Niels Bohr in Copenhagen on August 15, 1932. In this lecture, the text of which was later published in Nature (131:421-423,

Surface texture in the A and B phases of superfluid He-3 probed by surface state electrons – Kimitoshi Kono Thu. January 11th, 2007
4:15 pm-5:15 pm

We performed conductivity measurements of the 2D Wigner solid, which is an triangular array of electrons, on the surface of superfluid He-A and B phases under magnetic fields. The He-A phase has a nodal point of energy gap at North and South Poles of the Fermi sphere and is anisotropic. A unit vector directing from the South Pole to the North Pole is refered to as the L vector. Spatial orientational effect of the L vector is called a “texture”. The L vector preferentially aligns parallel to a surface normal. The conductivity of the Wigner solid is sensitive to the quasiparticle distribution,

Music Theory and Physics – Dmitri Tymoczko Thu. December 7th, 2006
4:15 pm-5:15 pm

I’ll talk about how music theorists encounter structures familiar from physics — symmetry groups, eigenvectors, gravitational fields, even — believe it or not — local U(1) gauge invariance.

Dark Energy: Taking Sides on the Issue [Joint Colloquium with Astronomy] – Rocky Kolb Thu. November 30th, 2006
4:15 pm-5:15 pm

All evidence for dark energy is indirect (as is the evidence for acceleration of the universe). In this colloquium I will discuss different approaches for interpreting the data usually said to be evidence for dark energy.

Electronic Motion in Molecular Circuits: Elastic Scattering and Beyond – Mark Ratner Thu. November 16th, 2006
4:15 pm-5:15 pm

Current experimental efforts are clarifying quite beautifully the nature of charge transport in so-called molecular junctions, in which a single molecule provides the channel for current flow between two electrodes. The theoretical modeling of such structures is challenging, because of the uncertainty of geometry, the nonequilibrium nature of the process, and the variety of available mechanisms. The talk will center on the first formulation of the problem in terms of scattering theory, and then on the generalizations needed to make that simple picture relevant to the real experimental situation. These include vibronic coupling, structural disorder and dephasing . Calculations of inelastic tunneling spectra,

Nanoparticle Liquid Crystals as Negative Index Materials – Peter Palffy-Muhoray Thu. November 9th, 2006
4:15 pm-5:15 pm

Light propagation in negative index materials (NIMs) is most unusual: light wave and energy travel in opposite directions. NIMs open the door to fundamentally new optical phenomena, and offer enormous potential for new device applications. Much of the current effort in this rapidly advancing field is aimed at realizing materials with a negative index at optical frequencies, where the wavelengths are five orders or magnitude smaller than in the microwave regime where negative refractive indices were first demonstrated.

NIMs do not exist in nature; they must be man made. Since characteristic lengths need to be on the nanometer scale,

The Cusp at Optimum Doping in the Low-Temperature Hall Number of the High-Temperature Superconductors – Greg Boebinger Wed. October 25th, 2006
4:15 pm-5:15 pm

After a brief overview of recent achievements at the National High Magnetic Field Laboratory (MagLab) using our pulsed, powered, and persistent magnets, I will focus on a series of my own experiments that utilized 60T pulsed magnetic fields to suppress the superconducting state in the high-temperature superconductors. The pulsed magnets are operated to the point of catastrophic stress failure…and occasionally, inadvertently, beyond. Oddly, however, they seem to offer the gentlest way to reveal the low-temperature normal-state of the cuprates in the absence of superconductivity. Evidence from resistivity measurements suggests a metal-insulator transition underlying the superconducting state. More recently [Nature 424,

Pollock’s Paintings: Are They Really Fractal? – Ellen Landau and Kate Jones-Smith Thu. October 19th, 2006
4:30 pm-5:30 pm

Ellen:
Motivated by a desire to assert the quality of his medium through gesture and materiality, Jackson Pollock’s allover paintings appear to stem from undirected manic motor activity, belying the extreme control of process which actually generated their abstract imagery. Moving far beyond traditional notions of subject or theme, Pollock created poured compositions in which the physical tracks of his bodily movements are permanently indexed. In his own words, Pollock’s goal was to express the “experience” of the modern age: “not an illustration of, but the equivalent.” Working directly with dripping fluid paint provided the key to his breakthrough achievement: an immediate statement of unconscious energy.

Physics is Fun — Odyssey of a Physics Entrepreneur – Ned Rasor Thu. October 12th, 2006
4:15 pm-5:15 pm

The personal realization that physics is fun and addicting began with a chain of accidental discoveries: discovery of physics as a non-academic profession, discovery of engineering physics, discovery of solid state and gaseous electronics, discovery of the management trap, and discovery of independent free-enterprise startups. Then the odyssey as a physics entrepreneur began. How easily a creative core of physicists formed an independent center of excellence doing what is fun in physics, but generating spin-off technologies and companies in the process, will be described along with the rules and strategies that perpetuated the fun for 25 years (plus 10 more years to date).

Dancing Fluids in Controlled Gravity – Charles Rosenblatt Thu. October 5th, 2006
4:15 pm-5:15 pm

Magnetic levitation techniques, whereby a strong magnetic field gradient partially or completely counteracts the Earth’s gravitational force, are applied to a variety of fluids problems.Ê Static properties are studied as a function of the effective gravitational force, and dynamic behavior is investigated by varying the magnet current temporally over time scales as fast as tens of milliseconds.Ê Results for the stability, collapse dynamics, and resonance behavior of liquid bridges in air will be presented.Ê Additionally, results on gravitationally-driven fluid interface instabilities will be discussed, showing how this technique facilitates measurements in regions of parameter space that are not possible using extant methods.

Is the Universe Out of Tune? – Glenn Starkman Thu. September 28th, 2006
4:15 pm-5:15 pm

It is a widely held view among cosmologists that our standard theory of cosmology — inflationary Lambda Cold Dark Matter — is so successful that cosmology now consists almost entirely of determining the parameters of the standard model to greater and greater accuracy. I will discuss how, at least on the largest scales, this is patently false. The fluctuations that we observe in the cosmic microwave background at the largest scale are far lower in amplitude than those predicted by our model. Furthermore, the little that there is aligns itself in bizarre ways, including aligning with the geometry of the solar system.

Many worlds in one – Alex Vilenkin Thu. September 21st, 2006
4:15 pm-5:15 pm

The new worldview that has emerged from recent developments in cosmology suggests that remote parts of the universe are in the state of explosive, accelerated expansion, called “inflation”. “Normal” regions, where inflation has ended, form islands in the ever-inflating sea. These “island universes” have a wide variety of physical properties and are constantly being produced. I will discuss the origin of the new worldview, its observational tests, and its bizarre implications.

“Recycling” Nuclear Power Plant Waste: Technical Difficulties and Proliferation Concerns – Ed Lyman Thu. September 14th, 2006
4:15 pm-5:15 pm

One of the most vexing problems associated with nuclear energy is the inability to find a technically and politically viable solution for the disposal of long-lived radioactive waste. The U.S. plan to develop a geologic repository for spent nuclear fuel at Yucca Mountain in Nevada is in jeopardy, as a result of managerial incompetence, political opposition and regulatory standards that may be impossible to meet. As a result, there is growing interest in technologies that are claimed to have the potential to drastically reduce the amount of waste that would require geologic burial and the length of time that the waste would require containment.

There is plenty of room at the bottom – Norman Tien Thu. September 7th, 2006
4:15 pm-5:15 pm

Richard Feynman gave a classic talk in 1959 envisioning the field of nanotechnology and inviting people to enter a new field of physics. Now, nearly 50 years later, we shall look at the issues and ideas that he presented and see how far we have moved toward his vision.

Neutrino Physics and Astrophysics: What we have learned and what we would like to discover – Nicole Bell Wed. May 3rd, 2006
4:15 pm-5:15 pm

Our knowledge of neutrino physics has undergone dramatic improvement in the last few years. We are now in the position to make confident predictions taking neutrino oscillations into account, opening the possibility to search for truly exotic particle physics within the neutrino sector, and to use neutrinos as reliable probes of astrophysics and cosmology. However, some very fundamental questions about neutrinos remain unanswered, such as whether their masses are of Dirac or Majorana type, or what the absolute neutrino mass scale is (oscillation experiments only reveal information about mass differences). We discuss implications of neutrino mixing for astrophysics and cosmology,

DNA Microtubules: a physical approach to synthetic biology – Deborah Fygenson Thu. April 27th, 2006
4:15 pm-5:15 pm

Microtubules are self-assembling/self-destructing tubular crystals of the protein tubulin that underpin the structure of most cells. Their dramatic dynamic instability has generated interest among biologists and physicists alike since its discovery in 1984, but still awaits a physical explanation. One reason is that tubulin is not amenable to the powerful expression and mutagenesis techniques of molecular biology. Another is that dynamic instability has no analog among non-biological materials. In this talk I will describe our approach to overcoming these challenges via “synthetic biology”. Briefly, we have developed a set of short sequences of DNA that use Watson-Crick base-pairing to self-assemble into tubular crystals which bear analogy to microtubules.

Confinement and Salt-Induced Long-Range Attraction in Colloids – Elshad Allahyarov Thu. April 13th, 2006
4:15 pm-5:15 pm

One of the long-standing problems in colloid science is whether there is like-charge attraction or repulsion between colloid particles in confinement and whether there are stable facets and voids in colloidal crystals. Using computer simulations with explicit microions, we show here that colloidal attraction is mediated via space charges opposite in sign to the colloidal charge. The space charging only occurs at low (but finite) added salt concentrations and in a complex geometric environment of the colloids. This implies a novel control over colloidal interactions and transport in charge-patterned microfluidic devices and has relevance for protein aggregation.

String Theory and Cosmology – Henry Tye Thu. April 6th, 2006
4:15 pm-5:15 pm

Recent advances in string theory leads naturally to an inflationary scenario that can be tested via cosmological observations.

Nematic Elastomers: Liquid Crystals and Fluid Solids – Robert Meyer Thu. March 30th, 2006
4:15 pm-5:15 pm

The combination of a nematic or cholesteric liquid crystal and a crosslinked polymer network, either an elastomer or a gel, is a classic example of a hyper-complex fluid system. The orientational interaction between polymer chains of the network and the long range ordering of the nematic phase links the two systems together. Elementary consequences of this linkage include the orienting effects of elastic strains of the gel on the nematic director, and conversely, nematic ordering induced strains of the gel network. However, there are surprising emergent properties of this combination of two complex fluid systems. Certain shear deformation modes of the polymer network lose their elastic restoring force,

A New Approach to Monte Carlo Methods in Statistical Physics – David Landau Thu. March 23rd, 2006
4:15 pm-5:15 pm
The two hydrogen economies – George Crabtree Thu. March 9th, 2006
4:15 pm-5:15 pm

Hydrogen offers a compelling solution to the energy challenges of supply, security, pollution, and climate change. Although today’s technology enables several routes for producing, storing, and using hydrogen, none of them are yet competitive with fossil fuels for cost, performance, or reliability. Dramatic advances in the basic understanding of hydrogen and its interactions with materials are needed to bring a hydrogen economy to practical realization. The current state of hydrogen technology and the research challenges for creating a mature hydrogen economy will be discussed.

Green Chemistry – Theory and Practice – Paul Anastas Thu. February 23rd, 2006
4:15 pm-5:15 pm
Relativity as a General Audience Course: The Inventor’s Paradox and the Explainer’s Paradox – Dan Styer Thu. February 9th, 2006
4:15 pm-5:15 pm

Through a decade of teaching special relativity to general-audience students, I have evolved a teaching strategy that combines numerical, algebraic, and qualitative reasoning. The course treats only space-time aspects of relativity, with no mention of momentum-energy. The non-science majors taking this course leave with an understanding of relativity that is in some ways demonstrably superior to the understanding shown by physics graduate students.

The Origin of Ultra High Energy Cosmic Rays: New Clues from the Pierre Auger Observatory – Corbin Covault Thu. January 26th, 2006
4:15 pm-5:15 pm

The origin of the highest energy cosmic rays has remained a profoundmystery for decades. Physicists are generally interested in cosmic ray sources as potential “beam generators”, providing a source of particles (including, perhaps, neutrinos) with energies far beyond that which could ever be achieved by particle accelerators on Earth. But arguably even more compelling is the underlying astrophysical mystery as to the nature of the accelerating engines for cosmic rays. Are ultra-high energy cosmic rays accelerated in jets of accreting black holes? Do they derive from relativistic shocks in intergalactic space? Are cosmic rays generated during gamma-rays burst events? Or do cosmic rays result from the decay of semi-stable super-massive particles left over from the Big Bang?

Single atom and single molecule manipulation with a scanning tunneling microscope – Saw-Wai Hla Thu. January 19th, 2006
4:15 pm-5:15 pm

The fascinating advances in single atom/molecule manipulations with the scanning-tunneling-microscope (STM)-tip allow scientists to fabricate artificial atomic scale structures, to study local quantum phenomena or to probe physical and chemical properties of matter at single atom and molecule level. Here, the STM is not only used to image single atoms/molecules but also used to manipulate them.

In this talk, our recent results of single atom/molecule manipulation experiments conducted by using a low temperature UHV-STM on metal and semiconductor surfaces will be presented. The presentation will include tunneling spectroscopy and manipulation of single silver atoms and vacancies, molecular wires such as sexi-phenyl,

Problem Solving and the Use of Math in Physics Courses – Joe Redish Thu. December 1st, 2005
4:15 pm-5:15 pm

Mathematics is an essential element of physics problem solving, but as professionals, we often fail to appreciate exactly what we are doing with it. Math may be the language of science, but math-in-physics is a distinct dialect of that language that requires both more subtlety and more skills than are typically taught in math courses. Research with students in classes ranging from algebra-based physics to graduate quantum mechanics indicates that (1) we sometimes don’t appreciate the skills students need to solve theÊproblems we assign, and (2) students problems are sometimes with their expectations about what they are supposed to be doing rather than with their math skills.

Plasmas as a Prototypical Complex System: Self-Organized Criticality as a Paradigm for Plasma Transport – David Newman Thu. November 17th, 2005
4:15 pm-5:15 pm

In nature there are many systems that exhibit some form of self-organization. Among these are forest fires, earthquakes, sandpiles, maybe sunspots and even life itself. Investigations into the similarity of the dynamics of such systems have been undertaken by using simple cellular automata models. These models have produced some important insight into the dynamics of such systems. Recently a Self-Organized Criticality (SOC) model for turbulent transport in magnetically confined plasmas has been proposed in order to explain some of the observed features of the transport dynamics in these plasmas. This model is based on the dynamics of a sandpile and has among others,

The calculation of electronic excitations in condensed matter – Lorin Benedict Thu. November 3rd, 2005
4:15 pm-5:15 pm

For twenty or more years, it has been possible to perform computations of material-specific ground state properties of solids, liquids, and molecules which agree very well with experiments. These calculations make use of theories in which the many-electron problem is replaced with an effective one-particle (mean field) problem. In the last decade it has become possible to perform calculations of low-lying excited states relevant for the accurate computation of various spectra such as photoemission and optical absorption. The theories underlying these computations are based on perturbation theory (often low order) in the screened electron-electron interaction, and seem to work very well for band insulators and metals.

Bending the quantum Hall effect: Novel one-dimensional metallic and insulating states – Matthew Grayson Thu. October 20th, 2005
4:15 pm-5:15 pm

Abstract: One-dimensional conductors are the wires that will connect the circuits of tomorrowÕs nanoworld, so it is important to characterize their possible conducting phases. We study a novel one-dimensional wire state which arises at the corner of two quantum Hall systems joined at a 90¡ angle, and observe both metallic,Êcritical,Êand insulating 1D behavior. Such non-planar confinement structures are unconventional for the quantum Hall effect and reveal the first observation of a macroscopic one- dimensional state whose conductance increases with decreasing temperature. This system can map out generic properties of one-dimensional disordered conductors since the metallic, critical, or insulating character is tunable with an external parameter,

Einstein 1905: The Standard of Greatness – John Rigden Thu. October 13th, 2005
4:15 pm-5:15 pm

In the short duration of six months, one week, and two days, Einstein, in 1905, wrote five papers that stand today at the bedrock of physics. In the context of 1905, only one of these papers was revolutionary. This paper, on the nature of light, made him the father of quantum physics. In the other four papers, Einstein clearly eschewed trivialities as he demonstrated the reality of atoms, established the dimensions of atoms, put the laws of thermodynamics on a new footing, established the validity of the kinetic theory, enhanced the significance of the speed of light, and purged the basic concepts of space,

2005 Robert Cherry Teaching Award Finalist Lecture: A Simple View of MRI and Its Rich View of Us – Robert Brown Thu. October 6th, 2005
4:15 pm-5:15 pm

With a reported 60 million scans made each year and the frequent news articles on what we are learning about our brain and how we think, magnetic resonance imaging (MRI) has become a major clinical and research phenomenon. We hope to discuss 1) the basic role of nuclei in generating pictures, 2) how to win and lose a Nobel Prize, 3) why MRI now is so important in the neuroscience world, 4) why we avoid the word “nuclear,” 5) why it would be marvelous if we could image you inside a very cold refrigerator, 6) a new lie detector and why someday we won’t need to give any more classroom exams.

The Origins of Microstructure: Dynamics and Patterning of Topological Defects in Soft and Hard Condensed Matter – Robin Selinger Thu. September 29th, 2005
4:15 pm-5:15 pm

Most condensed matter is riddled with defects that interrupt long-range order. Your house key, for instance, contains a network of grain boundaries and dislocations without which it would be too soft to hold its shape. Microstructure, the spatial arrangement of structural defects, both controls mechanical response and strongly affects transport properties. Understanding microstructure’s formation and evolution is a central goal of materials science research.

Defect-rich structures represent metastable states in most materials, and a sample will relax toward more complete long-range order when annealed. But curiously, there are many soft materials in which a defect-rich structure persists even in thermal equilibrium.

A Pocket-Sized Telling of the Genesis of the Greatest Ideas of the Greatest Thinker of All Time OR How Analogy Showed Einstein the Light, and How Light Showed Einstein the Universe – Douglas Hofstadter Thu. September 15th, 2005
4:15 pm-5:15 pm

Call it hubris or call it hubris squared, but somebody had to tackle it in this, the centenary of Albert Einstein’s “Annus Mirabilis” — “Miraculous Year” in Latin — and so I, once a physicist of sorts, and now a cognitive scientist fascinated by how people think, and in particular by the universality of analogy-making in human thinking, ranging from the most modest to the most exalted acts of cognition, inevitably found myself turning my metaphorical gaze to the above-mentioned thinker par excellence and reading his own papers as well as books and papers about him, in which, somewhat to my surprise and certainly to my deep gratification,

High Temperatures Superconductors: Recent Progress and Open Questions – Nandini Trivedi Thu. September 8th, 2005
4:15 pm-5:15 pm
Nanoscience with X-rays – Eric Isaacs Thu. April 21st, 2005
4:15 pm-5:15 pm

Future nanoscience and nanotechnologies, from quantum computation to light harvesting for energy and advanced medical therapies, will be based on new nanoscale materials and materials architectures that include quantum dots, photonic crystals, laterally confined inorganic and organic thin films and single molecules. In this talk, I will highlight recent advances at the Center for Nanoscale Materials at Argonne National Laboratory in the synthesis, self-assembly and characterization of nanostructured materials. I will emphasize how advanced x-ray techniques can address outstanding questions in nanoscale structure, dynamics and properties. Several recent examples include the x-ray visualization of the evolution of antiferromagnetic domain walls on the sub-micron scale in chromium,

Order on Curved Surfaces: Scars in Sphereland – Mark Bowick Thu. April 14th, 2005
4:15 pm-5:15 pm

Particles on a flat surface usually pack into a simple triangular lattice. How does this change if curvature is switched on? The minimum energy configuration for repulsively interacting particles on curved surfaces is a challenging problem with applications to mathematical physics, computer science and a variety of biological, chemical and condensed matter systems. I will discuss the universal proliferation of novel defect arrays (“scars”) in the ground state of such spherical crystals for sufficiently large systems, including experimental results for self-assembled spherical colloidal crystals.

Molecular and Phase Chirality in Polymer Networks – Eugene Terentjev Thu. April 7th, 2005
4:15 pm-5:15 pm

Nature appears to be inherently chiral. From the atomic scale with asymmetric carbon bonds, to much larger length scales like our hands or even spiral galaxies, all have the same common feature of lacking inversion symmetry, while not characterized by any vector (dipolar) property. In other words, many natural objects “know” the difference between right and left. This is the notion of chirality; since Pasteur and Kelvin in the mid-19 century it has always been a source of interest in various fields, from mathematics to medicine. Although stereo-specific intermolecular interactions are always very weak, there are many examples of macroscopic “phase chirality”

Precision Results from Lattice QCD – Claude Bernard Thu. March 31st, 2005
4:15 pm-5:15 pm

At present the only means of carrying out nonperturbative calculations of the Strong Interactions from first principles is through large scale numerical simulations of Quantum Chromodynamics (QCD) on the lattice. These simulations promise to make possible stringent experimental tests of the Standard Model, as well as searches for new physics. Here, I discuss recent advances in Lattice QCD simulations that allow us to make computations in which all systematic errors are under control. With better algorithms and huge amounts of computer power, the effects of virtual quark-antiquark pairs — long neglected in the so called “quenched approximation” — can now be included.

Do Quantum Dots Break Time-reversal Symmetry? – Harsh Mathur Thu. March 17th, 2005
4:15 pm-5:15 pm

Semiconductor quantum dots that contain a few hundred electrons have fascinating electronic properties shaped by the interplay of electron-electron interaction and randomness (due to chaotic scattering of electrons from device boundaries). Transport experiments that probe the electronic state and theoretical efforts to understand them will be reviewed. Our prediction of a new state of electronic matter in strongly interacting quantum dots will be discussed. In this novel electron liquid time-reversal symmetry is spontaneously broken and there is a persistent current in the electronic ground state even in the absence of superconductivity.

Transparent Conducting Oxides – Timothy Coutts Thu. March 3rd, 2005
4:15 pm-5:15 pm

In this talk, I shall begin by presenting some generalities about transparent conducting oxides (TCOs), including work at NREL, their typical properties and their relevance to solar cells. I shall demonstrate how a badly selected TCO can severely impact the performance of a new generation of high performance thin-film solar cells. I then demonstrate that the electron mobility of TCOs is the key property to which all investigations ought to focus. Only via high mobility can the dual requirements of excellent optical transmittance and electrical conductivity be achieved. Following this analysis, I apply the Drude theory to demonstrate that fundamental properties (such as the electron effective mass and relaxation time) of TCOs may be determined from their optical properties.

Searching for dark matter with liquid xenon – Tom Schutt Thu. February 24th, 2005
4:15 pm-5:15 pm
Towards First Glimpses of the Universe in Neutrinos – John Beacom Thu. February 17th, 2005
4:15 pm-5:15 pm

With the exception of the Sun and Supernova 1987A, no astrophysical sources of neutrinos have been detected yet. However, emerging developments give us great confidence that “first light” on extragalactic neutrino sources will soon be attained by terrestrial neutrino detectors. I will highlight the prospects for what we may learn about what lies beyond the standard model of particle physics and about the dynamics of the invisible universe.

Quantum-Limits in Mesoscopic Physics: From Quantum Noise to Qubits and Nanomechanics – Aashish Clerk Thu. February 10th, 2005
4:15 pm-5:15 pm

A number of recent experiments in mesoscopic physics have raised anew the question of what constitutes an “ideal” quantum detector, that is a detector which produces a minimal disturbance of the system being probed. I will discuss recent theoretical work addressing this issue, taking a point of view which stresses the physics of mesoscopic noise, and its connection to ideas from information theory. I will also discuss how these ideas apply to the quantum non-demolition measurement of a qubit, and to the study of nano-electromechanical systems.

Optical Signatures of the Aharonov-Bohm Phase in Carbon Nanotubes – Junichiro Kono Thu. February 3rd, 2005
4:15 pm-5:15 pm

Single-walled carbon nanotubes, tubular crystals of sp2-bonded carbon atoms that are just one atom thick, come in different varieties, each with a subtle difference in structure and properties – some of them are metals and others are semiconductors. This talk will describe magneto-optical studies on carbon nanotubes in high magnetic fields, which confirm theoretical predictions that the band structure of a carbon nanotube is dependent on the magnetic flux threading the tube, in a truly unique manner. We observed significant field-induced optical anisotropy as well as red shifts and splittings of absorption and photoluminescence peaks. The amounts of shifts and splittings depend on the value of the magnetic flux and are quantitatively consistent with theories based on the Aharonov-Bohm effect.

Connecting the Dark Side and Fundamental Physics – Mark Trodden Thu. January 27th, 2005
4:15 pm-5:15 pm

The universe is composed of normal matter, dark matter and a component that is causing cosmic acceleration. The existence of all three of these components poses a challenge to fundamental physics; the nature of dark matter remains unknown, dark energy or its equivalent is a complete mystery and even baryons, which we see all around us, should have annihilated with their antiparticles long before galaxies formed. In this colloquium I will briefly review the evidence for each of these components before discussing the associated problems and their possible resolutions. The focus will on the importance of connecting cosmic observations with both theoretical and experimental progress in fundamental physics.

Functional and Morphological Imaging of the Human Brain using Magnetic Resonance Imaging – E. Mark Haacke Thu. January 20th, 2005
4:15 pm-5:15 pm

Magnetic resonance imaging is an ever developing area that makes it possible to image the human body in vivo. The development of nuclear magnetic resonance in physics has led to multiple Nobel Prizes in various fields. The two most recent are in MR imaging for Paul Lauterbur and Peter Mansfield. That this should be so is evidenced by the amazing number of clinical and technical applications of this methodology. Today we can image down to resolutions of a few hundred microns in vivo, we can watch the brain at work and we can measure chemical processes in action. In this presentation,

Dynamics of electron-phonon systems – Stuart Trugman Thu. December 9th, 2004
4:15 pm-5:15 pm

We consider the quantum physics of correlated systems, with a focus on electron-phonon coupled systems. The static and dynamic formation properties of a polaron quasiparticle are calculated with surprising accuracy, and compared to experiment. The successes and failures of certain computational schemes force one reluctantly to confront fundamental issues in quantum mechanics.

Aerosil Nanoparticles in Liquid Crystals: Order, Disorder, Transitions and lots more – Dan Finotello Thu. December 2nd, 2004
4:15 pm-5:15 pm
Surfactant and Geometric Effects on Interfacial Stability – David Rumschitzki Thu. November 18th, 2004
4:15 pm-5:15 pm
Ultrafast Dynamics in Complex Materials – Antoinette J. Taylor Mon. November 15th, 2004
4:15 pm-5:15 pm

I will discuss the development and application of novel optical spectroscopic techniques to the study of ultrafast dynamics in complex materials. I will first describe all-optical pump probe and optical-pump far-infrared probe experiments on (a) colossal magnetoresistance manganites, (b) superconductors, and (c) heavy fermion materials. The experimental techniques are discussed followed by a brief review of ultrafast electron dynamics in conventional wide band metals that serves as a starting point in understanding dynamics in more complex systems. In. half-metallic manganites, the quasiparticle dynamics in the ferromagnetic metallic state can be understood in terms of a dynamic transfer of the spectral weight which is influenced by the lattice and spin degrees of freedom.

Prospects for CMB observations – Stephan Meyer Thu. November 11th, 2004
4:15 pm-5:15 pm

Cosmic Microwave Background (CMB) radiation observation is the most important and cleanest probe of the early universe. Currently, most of the information comes from the large-scale temperature spatial power spectrum which is directly coupled to early universe physics and largely uncontaminated by astrophysical foreground emission. Future CMB measurements promise to provide further tests of early universe conditions and evolution. Small-scale temperature anisotropy and polarization measurements will tell us about the formation and evolution of the earliest structures and possibly even detect evidence for horizon-scale gravity-waves left over from the inflationary epoch. However, these measurements pose very considerable new challenges both because of contamination from foreground emission which will no longer be unimportant,

Solar photovoltaics – Larry Kazmerski Thu. November 4th, 2004
4:30 pm-5:30 pm

Solar photovoltaic (PV) technology has advanced rapidly since the crystalline-silicon solar cell of a half-century ago. Have we arrived at our final destination? No, not yet. This presentation examines the current, near-term, and next-generation PV technologies-looking back to where we have been and forward to where we are going – and provides a critical evaluation of our needed research directions.

Putting the Mechanics back into Quantum Mechanics – Keith Schwab Thu. October 21st, 2004
4:15 pm-5:15 pm

I will discuss our recent experiments where we have made the closest approach to the quantum limit for continuous position detection of a mechanical structure, a factor of ~5 from the uncertainty principle limit. We have developed a nano-electro-mechanical device with an integrated nanomechanical resonator and ultra-sensitive single electron transistor. The success of these experiments paves the way to the realization of truly quantum states of the mechanical device: squeezed states, number states, and most exciting, the formation of mechanical entangled states. I will also discuss the applications of this technology from advanced force microscopes to readout for quantum information devices.

Observation of Superflow in Solid Helium – Moses Chan Thu. October 14th, 2004
4:15 pm-5:15 pm

We report on the observation of non-classical rotational inertia behavior in solid He-4 confined to an annular channel in a sample cell under torsional motion, demonstrating superfluid behavior. The effect shows up as an abrupt drop in the resonant oscillation period as the sample cell is cooled below 230 mK. Measurement of 17 solid samples allows us to map out the boundary of this superfluid-like solid or supersolid phase from the melting line up to 66 bars. This experiment indicates that superfluid behavior is found in all three phases of matter, gas, liquid and solid. This work is done in collaboration with Eunseong Kim and is supported by the Condensed Matter Physics program of NSF.

Physics and Society – Bill Fickinger, Cyrus Taylor, and Phil Taylor Thu. October 7th, 2004
4:15 pm-5:15 pm

The three speakers will describe some of the contributions physicists are currently making to the well-being of the nation.

Our energy challenge – Richard Smalley Thu. September 23rd, 2004
4:30 pm-5:30 pm

Within the next few decades, we must find an energy source of at least 10 terawatts (TW) of cheap, clean power. In order for the billions of people in the developing world to achieve and sustain a modern lifestyle, we really need 50 TW. Who will make the necessary scientific and engineering breakthroughs? Can they be done soon enough to avoid the hard economic times, terrorism, war and human suffering that will otherwise occur?

Ferroelectric liquid crystals: Realities and possibilities – Rolfe Petschek Thu. September 16th, 2004
4:15 pm-5:15 pm

Ferroelectric liquid crystals are of scientific interest and also have a variety of potential applications. I will review the various ways in which people have proposed to, claimed to, or succeeded in making ferroelectric liquid crystals, and suggest why it is “hard”. I will also suggest new possible ways to make such phases, and in particular ideas for and constraints on the formation of ferroelectric nematic phases.

Reception to welcome new members of the department Thu. September 9th, 2004
4:30 pm-5:30 pm
The Fourth Decade … and my introductory physics class this fall – Robert Brown Thu. September 2nd, 2004
4:15 pm-5:15 pm

A lecture given on the occasion of receiving the national 2004 AAPT Excellence in Undergraduate Teaching Award
I describe the beginning of my fourth decade of undergraduate teaching, a story that has astonished me with how fast it is changing. In the first decade, frantic memories abound of realizing just how much I did not know about the class material I was slated to teach (sometimes the next day!). The second decade taught me how even very young undergraduates could contribute to even very theoretical research programs and could understand even very fancy nonlinear physics. The third decade found me using e-mail,

Out of gas: the end of the age of oil – David Goodstein Thu. August 26th, 2004
4:30 pm-5:30 pm

The world will start to run out of cheap, conventionally produced oil soon, possibly within this decade. This talk will discuss the reasoning that leads to this conclusion and the likely consequences if it is correct. It may be possible, with considerable difficulty, to substitute other fossil fuels for the missing oil. Even then, we will ultimately run out of all fossil fuels, probably within this century. Can civilization survive if this happens? We will consider the possibilities.

Recent Discoveries in Neutrino Physics – Karsten Heeger Wed. April 28th, 2004
4:15 pm-5:15 pm

Neutrino mass and mixing are amongst the major discoveries of recent years. From the observation of neutrino flavor change in solar and atmospheric neutrino experiments to the measurements of neutrino mixing with terrestrial neutrinos, recent experiments have revealed new particle properties of neutrinos and provided the first hint of physics beyond the Standard Model of particle physics. These observations have helped solve the long-standing Solar Neutrino Problem, the apparent deficit of the observed electron solar neutrino flux, and have contributed to a better understanding of the role of neutrinos in the Universe. A broad field of neutrino research has emerged in particle,

Organic-Based Magnets: New Materials, New Phenomena, And New Applications – Art Epstein Thu. April 22nd, 2004
4:15 pm-5:15 pm

Magnets utilizing organic groups with essential spin have been reported since the mid-1980s. Though initial organic-based magnets (OBMs) had magnetic ordering temperatures (Tc’s) below 5K, OBMs now have Tc’s up to 400K. The chemical control of OBMs will be introduced. In addition to magnetic phenomena already known for conventional transition metal and rare earth magnets, OBMs feature unique phenomena enabled by the shape and internal electronic structure of the organic molecules. Examples are illustrated with experimental results for magnets based on tetracyanethylene, [TCNE], which as an anion has spin ¸. For example, application of blue light to Mn++[TCNE]-2 increases the magnetic susceptibility below the Tc of 75 K and green light reverses the effect.

Revitalizing the Upper-Division Physics Curriculum – Corinne Manogue Thu. April 15th, 2004
4:15 pm-5:15 pm

The Paradigms in Physics Program at Oregon State University has totally reformed the entire upper-division curriculum for physics and engineering physics majors. This has involved both a rearrangement of content to better reflect the way professional physicists think about the field and also the use of a number of reform pedagogies which place responsibility for learning more firmly in the hands of the students. Along the way we are learning about what it takes to successfully design and implement large scale modifications in curriculum and to institutionalize and disseminate them. The particular emphasis will be on how our reforms have influenced how we teach quantum mechanics.

Helix-Coil Transition of Worm-like Polymers – Gustavo Carri Thu. April 8th, 2004
4:15 pm-5:15 pm

Many macromolecules like proteins and polypeptides are known to form secondary structures called a-helices at low enough temperatures or under appropriate solvent conditions. The transition from the ordered state (a-helix) at low temperatures to the disordered one (random coil) at high temperatures is called the helix-coil transition. Simulating this transition and the resulting physical behavior of a-helices has proven to be a very challenging task even for modern computational systems. In this talk I will present a novel geometric approach to the simulation of the helix-coil transition in worm-like polymers. This approach combines the traditional statistical-mechanical concepts proposed by Zimm,

Physics Education Research: Closing the gap between what we teach and what is learned – Chandralekha Singh Thu. April 1st, 2004
4:15 pm-5:15 pm

Despite our best and most sincere efforts, there is an alarming disconnect between what we teach and what students learn and understand. The goal of physics education research is to help close this gap. I will discuss, using my own research and activities as examples, the three major components of physics education research: (1) Identification of student difficulties, (2) curriculum/pedagogy development to minimize the sources of these difficulties, and (3) implementation/evaluation of new pedagogy and teaching methods. My own research has emphasized student understanding of basic (energy/momentum) and advanced (quantum mechanics) concepts, and has strived to find common origins for the ways in which misconceptions arise.

Quantum Computers and Decoherence: Exorcising the Demon from the Machine – Daniel Lider Thu. March 18th, 2004
4:15 pm-5:15 pm

Recently discovered algorithms indicate that quantum computers may one day enable exponentially faster computation than is fundamentally possible using their classical counterparts. The realization of this promise hinges above all on the ability to protect quantum computers against the deleterious effect of the interaction with their environment, leading to decoherence. A decohered quantum computer is equivalent to a badly malfunctioning classical computer. In this talk the what’s, why’s, how’s and problems of quantum computation will first be briefly reviewed. This will be followed by a proposal for a solution of the decoherence problem, with applications to atomic and solid-state quantum computing.

Quenched Disorder in Soft Materials: Helical Polymers and Liquid-Crystalline Elastomers – Jonathan Selinger Mon. March 8th, 2004
4:00 pm-5:00 pm

In statistical mechanics, the term “quenched disorder” refers to heterogeneity that is fixed, unable to respond to changes in a material. Thermal fluctuations and quenched disorder are two distinct types of randomness that can control the statistical mechanics of condensed matter. In soft materials, thermal fluctuations usually dominate because heterogeneities are free to move around a sample. However, recent research has found certain types of soft materials where quenched disorder plays the dominant role. In this talk, we present theoretical models for two such systems. For helical polymers, including polyisocyanates and DNA, we show that the helical order of the chains is controlled by the disordered sequence of monomer units.

Causal sets as the deep structure of spacetime – Fay Dowker Thu. February 26th, 2004
4:15 pm-5:15 pm

One approach to solving the problem of quantum gravity is based on the causal set hypotheis, which states that the deep, quantum structure of spacetime is discrete and is what is known in mathematics as a “partial order” or “poset”, a kind of extended family tree. Causal set theory has now reached a stage at which questions of phenomenology are beginning to be addressed. this talk will introduce the basic concepts and motivations behind the hypothesis and address some of the latest developments which include: (i) an apparently confirmed order of magnitude prediction for the cosmological constant, the only prediction made in any propsed theory of quantum gravity that has been subsequently verified by observation (ii) a classical stochastic causal set dynamics which arguably is the most general consistent with the discrete analogs of general covariance and classical casuality (iii) a rigorous characterization of the observables (or “physical quetions”) of causal set cosmology,at least in the classical case.

The Full Mottness: Asymptotic Slavery – Philip Phillips Thu. February 12th, 2004
4:15 pm-5:15 pm

Vast progress in theoretical solid state physics has been made by constructing models which mimic the low-energy properties of solids. Essential to the success of this program is the separability of the high and low energy degrees of freedom. While it is hoped that a high energy reduction can be made to solve the problem of high temperature superconductivity in the copper oxide materials, I will show that no consistent theory is possible if the high energy scale is removed. At the heart of the problem is the mixing of all energy scales (that is, UV-IR mixing) in the copper-oxide materials.

Shedding Light on Dark Energy with SNAP – Gregory Tarle Thu. February 5th, 2004
4:15 pm-5:15 pm

Recent experiments have confirmed that the universe is expanding at an ever-increasing rate, driven by a presently unknown form of “dark energy.” To determine what the dark energy is as opposed to that it is will require a new generation of experiments of unprecedented precision. An international team of scientists is now planning for a SuperNova /Acceleration Probe (SNAP), a new type of space telescope with a wide field optical-to-near-infrared imager and spectrograph. SNAP will observe thousands of supernovae over a wide range of redshifts to measure the expansion history of the universe. By examining how the equation of state of the universe evolves over cosmological time,

Physics Tricks for Fun and Profit: a Physicist’s Adventures in Theoretical Ecology – Robin Snyder Thu. January 29th, 2004
4:15 pm-5:15 pm
The D0 Experiment at the Fermilab Tevatron: Recent Results and Prospects – Mike Hildreth Thu. January 15th, 2004
4:15 pm-5:15 pm

Last summer, the Tevatron experiments released the first physics results based on the substantial quantity of data collected so far in Run II. I will give an overview of the broad physics program that will be accessible with the expected Run II dataset that is 20-100 times larger than what we have now. This will include recent results and future projections for our studies of the origin of mass (the Higgs boson?), the discovery of new forms of matter (Dark Matter? Supersymmetry?), and the potential explorations of new large extra space-time dimensions, if they exist.

Structural Studies of Alzheimer’s Amyloid Fibrils by NMR: Where’s the Physics? – Rob Tycko Thu. May 9th, 2002
4:15 pm-5:15 pm

Amyloid fibrils are filamentous structures with remarkably similar morphologies formed by a variety of polypeptides with remarkably dissimilar amino acid sequences. We are using novel nuclear magnetic resonance (NMR) techniques to investigate the molecular structures of amyloid fibrils, especially amyloid fibrils that deposit in the brains of Alzheimer’s disease patients. Physics plays two roles in this highly interdisciplinary work: (1) fundamental physical issues, such as the nature of interactions that stabilize amyloid fibrils, are unresolved and motivate our measurements; (2) the NMR techniques themselves involve interesting physical principles and phenomena. Our most recent progress will be described, with an emphasis on the physical science aspects.

Cosmic Inflation and the Arrow of Time – Andreas Albrecht Thu. May 2nd, 2002
4:15 pm-5:15 pm

Cosmic inflation claims to make the initial conditions of the standard big bang “generic”. But Boltzmann taught us that the arrow of time arises from very non-generic (“low entropy”) initial conditions. I discuss how to reconcile these perspectives. The resulting insights give an interesting way to understand and compare inflation and other ideas that purport to offer alternatives to inflation.

QCD and Natural Philosophy – Frank Wilczek Thu. April 25th, 2002
4:15 pm-5:15 pm

QCD allows us — indeed, invites us — to address some basic questions from a new perspective, and with much greater precision than was possible before. These include the origin of mass, the feebleness of gravity, the `specialness’ of the parameters required to support life (anthropic principle), the nature of fundamental versus effective theories, and the computability of physical laws. I’ll describe the insights that QCD affords into these issues.

The Universe’s Unseen Dimensions – Gia Dvali Thu. April 18th, 2002
4:15 pm-5:15 pm

The visible world could lie on a membrane floating in higher-dimensional space. The extra dimensions would explain the weakness of gravity and the origin of the minuscule “dark” energy in the Universe. If so, the new dimensions, black holes, quantum gravity and string theory may become experimentally accessible in this decade.

Magnetic Resonance Imaging: Applied Physics and Electromagnetics – William A. Edelstein Thu. April 11th, 2002
4:15 pm-5:15 pm

Magnetic Resonance Imaging (MRI) is the most novel and important medical imaging modality since the advent of the X-ray. MRI grew out of the long development by physicists of atomic spectroscopy, atomic and molecular beam resonance and, finally, nuclear magnetic resonance (NMR) in condensed matter. The operation and economics of MRI systems depend critically on the performance of magnets, pulsed magnetic field gradient windings and rf coils, and necessity has spurred development of much science and innovative technology in these areas. Superconducting magnets have come to be the magnet of choice because of their ability to produce strong, stable, homogeneous magnetic fields (0.5 T to 8 T) in large enough volumes to accommodate human subjects.

Exciting the Eccentricity of Extrasolar Planets – Re’em Sari Thu. April 4th, 2002
4:15 pm-5:15 pm

The detection of extrasolar planets is one of the great scientific discoveries of the past decade. Most of these planets planets move on orbits with substantial eccentricities. The origin of these large eccentricities is an unsolved puzzle. We propose that they result from the exchange of angular momentum and energy between the planets and the disks from which they form. These interactions are concentrated at discrete Lindblad and corotation resonances. We describe the physics of these resonances and their effects on the planets migration and eccentricity evolution. If both resonances are fully active, the rate of eccentricity damping by corotation resonances is slightly larger than its excitation rate by Lindblad resonances and the eccentricity decays.

Nonlinear Optics, Quantum Optics and Ultrafast Phenomena with X-Rays from Synchrotrons and Free-Electron Lasers – Bernhard Adams Thu. March 28th, 2002
4:15 pm-5:15 pm

In the last few decades, x-ray physics has made tremendous advances, and the development is expected to accelerate with the advent of x-ray free-electron lasers (XFEL). An XFEL will emit transversely fully coherent x-ray pulses of ca. 100fs duration at a peak power of 1010W . The LCLS project at Stanford and TESLA at DESY, Hamburg are in the advanced stages of planning and scientific cases were developed. A few examples from the fields of nonlinear optics, quantum optics, and the study of ultrafast phenomena will be presented in the talk and results from some experiments in these fields that have recently been done at synchrotron radiation facilities will also be mentioned.

Laser-induced phase transformations on a nanoscale – Vladislav Yakovlev Thu. March 14th, 2002
4:15 pm-5:15 pm

Nanotechnology, once a wonderful dream, is now becoming a reality. In order to selectively modify and construct nanodevices we have to understand how materials transform from one form to another on a nanoscale. Short-pulsed lasers and optical spectroscopic techniques serve as a unique set of tools and methods to initiate and control phase transformations and to study their dynamics on the appropriate time-scale. In my presentation I will review our recent results on the laser-induced phase transformations and outline the current trends of spectroscopic techniques for their diagnostics.

New Physics and Cosmology from Extra Dimensions – Nemanja Kaloper Thu. March 7th, 2002
4:15 pm-5:15 pm

Consistent formulations of string theory require the existence of additional spatial dimensions. These extra dimensions can play a crucial role in determining the properties of our Universe, shedding new light on some of the greatest mysteries of nature, such as the observed weakness of gravity. If the extra dimensions are as large as the current observational limit at a sub-millimeter scale, they lead to an exciting possibility of testing string theory in the near-future collider experiments and in cosmology. I will discuss how such models emerge from string theory, showing why they are plausible and what are their experimental consequences and predictions.

What’s Kelvin’s Problem? – Randall D. Kamien Thu. February 28th, 2002
4:15 pm-5:15 pm

We discuss the physics and mathematics of sphere packing and minimal surfaces and use these to explain the crystal symmetries found in macromolecular, supramolecular micellar materials and charged colloids. In the case of molecular assemblies, we argue that the packing entropy of the hard micellar cores is frustrated by the entropic interaction of their brush-like coronas. The observed crystal structures correspond to the Kelvin and Weaire-Phelan minimal foams. We show that these structures are stable for reasonable areal entropy densities.

Getting a Handle on Spintronics with Optical Spin Electrodes – Jay Kikkawa Thu. February 21st, 2002
4:15 pm-5:15 pm

Spintronics is an emerging field aimed at using the electron’s spin instead of its charge for information processing and computation. This talk will describe how basic research in this field employs beams of light that behave analogously to conventional electrodes. We will provide an overview of recent fast optical experiments that reveal how the electron’s spin memory in semiconductors is influenced by electrical doping, spatial motion, interfaces, and hyperfine interactions. In the latter case, electron spins not only serve as a magnetometer of local nuclear fields, but can also be used to induce NMR with near-visible light rather than conventional radio-frequency fields.

Luminosity in the Fermilab Tevatron – Mike Martens Thu. February 7th, 2002
4:15 pm-5:15 pm

The Fermilab Tevatron collides protons with antiprotons to create luminosity at a center of mass energy of 1.96 Tev. This talk will start with a description of the steps performed as protons and antiprotons make their way through the chain of Fermilab accelerators before reaching the Tevatron. The rest of the talk will focus on the Tevatron, the factors that determine the luminosity, and some of the fundamental limitations of creating luminosity.


Scroll To Top