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## Physics

### Upcoming Events

 Event Date Summary Carlos Arguelles Delgado (Harvard University) Thu. September 24th, 2020 4:00 pm-5:00 pm Link to video Challenging the Standard Model With High-Energy Neutrinos Particle physicists are living in interesting times. We are faced with the paradox of a highly predictive theory –the Standard Model — that is filled with patterns that are hard to explain. We are also faced with “known unknowns,” like dark matter. Right now, neutrinos are the only particles exhibiting beyond Standard Model behavior, seen in the flavor transitions called neutrino oscillations, which are due to neutrino mass. This is an important clue towards a larger theory. Building on this, I am interested in what other types of flavor transitions neutrinos may have due to new particles, Continue reading… Carlos Arguelles Delgado (Harvard University) Xiaoju Xu (CWRU) Tue. September 22nd, 2020 11:30 am-12:30 pm Halo and galaxy assembly bias Measuring galaxy clustering is an effective way to gain knowledge of galaxy formation and constraining cosmology. Cosmology determines dark matter halo population and clustering, and halo clustering and halo occupation determine the galaxy clustering. It is important to understand halo clustering and galaxy-halo connection to build halo occupation models. In N-body simulations, halo clustering is shown to depend not only on halo mass but also on secondary halo properties, which is called the halo assembly bias. However, traditional halo occupation models only consider halo mass dependence and ignore effects caused by secondary halo properties. Continue reading… Xiaoju Xu (CWRU) Matthew Yankowitz (University of Washington) Mon. September 21st, 2020 12:45 pm-1:45 pm Tunable correlated and topological states in twisted graphene heterostructures Matthew Yankowitz Department of Physics, University of Washington Zoom Recording Abstract.– In van der Waals heterostructures composed of two rotated graphene sheets, a moiré superlattice results in the emergence of flat electronic bands over a small range of twist angles. A variety of highly tunable correlated and topological states have recently been identified in these platforms owing to the quenched kinetic energy of charge carriers and the intrinsic Berry curvature of the flat bands. I will discuss our recent work investigating these states in three different twisted graphene platforms. Continue reading… Matthew Yankowitz (University of Washington) Axel Hoffmann (University of Illinois, Urbana-Champaign) Thu. September 17th, 2020 4:00 pm-5:00 pm Link to video Topological Quasiparticles: Magnetic Skyrmions The field of spintronics, or magnetic electronics, is maturing and giving rise to new subfields [1].  An important ingredient to the vitality of magnetism research in general is the large complexity due to competitions between interactions crossing many lengthscales and the interplay of magnetic degrees of freedom with charge (electric currents), phonon (heat), and photons (light) [2].  One perfect example, of the surprising new concepts being generated in magnetism research is the recent discovery of magnetic skyrmions.  Magnetic skyrmions are topologically distinct spin textures that are stabilized by the interplay between applied magnetic fields, Continue reading… Axel Hoffmann (University of Illinois, Urbana-Champaign) Gordan Krnjaic (Fermilab) Tue. September 15th, 2020 11:30 am-12:30 pm A Dark Matter Interpretation of Excesses in Multiple Direct Detection Experiments We present a novel unifying interpretation of excess event rates observed in several dark matter direct-detection experiments that utilize single-electron threshold semiconductor detectors. Despite their different locations, exposures, readout techniques, detector composition, and operating depths, these experiments all observe statistically significant excess event rates of ~10 Hz/kg. However, none of these persistent excesses has yet been reported as a dark matter signal because their common spectral shapes are inconsistent with dark matter particles scattering elastically off detector nuclei or electrons. We show that these results can be reconciled if the semiconductor detectors are seeing a collective inelastic process known as a plasmon. Continue reading… Gordan Krnjaic (Fermilab) No seminar (faculty meeting) Mon. September 14th, 2020 12:45 pm-2:00 pm Continue reading… No seminar (faculty meeting) Guilherme Pimentel (Amsterdam, Leiden) Thu. September 10th, 2020 4:00 pm-5:00 pm Decoding Primordial Fluctuations   All the information we will ever obtain from the primordial universe is imprinted in the spatial correlations of fluctuations at the hot Big Bang. I will explain how an influx of ideas from various areas of fundamental physics is providing us with new conceptual and practical tools to decode the physics of these primordial fluctuations. A thorough understanding of the fluctuations will give us insight into particle physics at the highest energies and may provide a window into the nature of spacetime itself.   Continue reading… Guilherme Pimentel (Amsterdam, Leiden) Hooman Davoudiasl (Brookhaven) Tue. September 8th, 2020 11:30 am-12:30 pm Ultralight Fermionic Dark Matter Tremaine and Gunn argued long ago that fermionic dark matter lighter than a few hundred eV is not feasible, based on the Pauli exclusion principle. We highlight a simple way of evading this conclusion which can lead to various interesting consequences. In this scenario, a large number of fermionic species with quasi-degenerate masses and no couplings, other than gravitational, to the standard model are assumed. Nonetheless, we find that gravitational interactions can lead to constraints on the relevant parameter space, based on high energy data from the LHC and cosmic ray experiments, Continue reading… Hooman Davoudiasl (Brookhaven) Pietro Gambardella (ETH Zürich, Switzerland) Mon. September 7th, 2020 12:45 pm-1:45 pm Charge-spin conversion effects and magnetization switching enabled by spin-orbit coupling Pietro Gambardella Department of Materials, ETH Zurich, CH – 8093 Zürich, Switzerland Zoom Recording The coupling of spin and orbital angular momenta underlies the magnetoelectric properties of matter. Although small, the spin-orbit interaction determines the preferred orientation of the order parameter in ferromagnets and antiferromagnets as well as the possibility to excite the magnetization out of equilibrium while ensuring the conservation of angular momentum. In recent years, advances in the understanding of the nonequilibrium charge-spin conversion processes mediated by the spin-orbit interaction have opened new perspectives for controlling the static and dynamic magnetization of all classes of magnetic materials, Continue reading… Pietro Gambardella (ETH Zürich, Switzerland) Aviva Rothman (CWRU History) Thu. September 3rd, 2020 4:00 pm-5:00 pm Link to video Conversations with the Starry Messenger: Kepler, Galileo, and the New Science Upon hearing of Galileo’s new telescopic discoveries, Kepler wrote a book in support of Galileo’s work.  Yet that book was read by many as an indictment of Galileo, rather than a defense.  This story, and the subsequent relationship between these two famous astronomers, will shed light on the contested nature of science at the dawn of the telescopic age, and on alternate visions of what the ideal scientist ought to be like. Saurabh Kumar (CWRU) Tue. September 1st, 2020 11:30 am-12:30 pm Radiating Macroscopic Dark Matter Dark matter is believed to constitute about 5/6th of the matter in the universe, but its nature and interactions remain one of the great puzzles of fundamental physics. Despite extensive experimental efforts, there have been no widely believed detections of WIMPS, axions or any other physics Beyond the Standard Model (BSM) (except for neutrino oscillations, which are BSM principally by historical accident). The question then arises: could the Standard Model, the most accurate and extremely well-tested theory of all observed particles in nature, explain dark matter as well? Many models of exotic quark matter have been proposed, Continue reading… Saurabh Kumar (CWRU) Yi Li (Argonne National Lab) Mon. August 31st, 2020 12:45 pm-1:45 pm Coherent information processing with on-chip microwave magnonics Zoom Recording In the race of post-CMOS computing technologies, coherent information processing with microwave circuits have demonstrated great potentials with the recent breakthrough in quantum computing, where both the quanta and the phase of the excitation states can be utilized for carrying and processing information. In this seminar, I will show that magnons—the collective excitations of exchange-coupled spins in magnetic materials—act as a new candidate for coherent information transfer and processing. Compared with other excitations, magnons exhibit special advantages: 1) their frequencies are naturally in the microwave regime and can be noninvasively tuned by an external magnetic field, Continue reading… Yi Li (Argonne National Lab) Jie Shan (Cornell) Thu. April 23rd, 2020 4:00 pm-5:00 pm Continue reading… Jie Shan (Cornell) Postponed: Aashish Clerk , University of Chicago Mon. April 20th, 2020 12:45 pm-1:45 pm TBA Host: Harsh Mathur Continue reading… Postponed: Aashish Clerk , University of Chicago RESCHEDULED Axel Hoffmann (Univ Illinois, Urbana-Champaign) Thu. April 16th, 2020 4:00 pm-5:00 pm New Date to be determined Continue reading… RESCHEDULED Axel Hoffmann (Univ Illinois, Urbana-Champaign) Sveta Morozova, Department of Macromolecular Science and Engineering, Case Western Reserve University Mon. April 13th, 2020 12:45 pm-1:45 pm TBA   Host: Lydia Kisley Continue reading… Sveta Morozova, Department of Macromolecular Science and Engineering, Case Western Reserve University RESCHEDULED Terry Sejnowski (Salk Institute) Thu. April 2nd, 2020 4:00 pm-5:00 pm Rescheduled for Fall 2020 Continue reading… RESCHEDULED Terry Sejnowski (Salk Institute) CANCELLED until later notice: Prof. Liuyan Zhao, University of Michigan,Ann Arbor, Complex magnetic excitations in a honeycomb ferromagnet CrI3 Mon. March 30th, 2020 12:45 pm-1:45 pm Complex magnetic excitations in a honeycomb ferromagnet CrI3 Liuyan Zhao, Department of Physics, University of Michigan, Ann Arbor Two-dimensional (2D) honeycomb ferromagnetic monolayers are predicted to host massless Dirac magnons because of the two equivalent magnetic sites per unit cell of the honeycomb lattice, mimicking Dirac electrons in graphene. More interestingly, the introduction of the next-nearest-neighbor Dzyaloshinskii-Moriya interaction breaks the sublattice equivalency and suggests the emergence of topological magnons in these honeycomb ferromagnets. Recenly, CrI3, a honeycomb ferromagnet, has attracked tremendous attention because of the long-range 2D ferromagnetic order in its monolayer, the interlayer antiferromagnetic order in its few layers, Continue reading… CANCELLED until later notice: Prof. Liuyan Zhao, University of Michigan,Ann Arbor, Complex magnetic excitations in a honeycomb ferromagnet CrI3 RESCHEDULED Ken Singer et al (CWRU Physics and Art History) Thu. March 26th, 2020 4:00 pm-5:00 pm New date to be determined Data Science in Art: Discerning the Painter’s Hand Ken Singer, Ambrose Swasey Professor of Physics with Michael Hinczewski, Assistant Professor of Physics Ina Martin, Senior Research Associate (Physics), Adjunct Faculty in the Department of Materials Science and Engineering Betsy Bolman, Elsie B. Smith Professor in the Liberal Arts and Chair, Department of Art History and Art  The Departments of Art History and Art, Physics, Materials Science and Engineering, the Cleveland Museum of Art and the Cleveland Institute of Art have been collaborating to investigate the application of machine learning (ML) to artist attribution based on confocal optical profilometry data from student-produced painting via the brushstroke texture.  Continue reading… RESCHEDULED Ken Singer et al (CWRU Physics and Art History) RESCHEDULED Robin Selinger (Kent State) Thu. March 19th, 2020 4:00 pm-5:00 pm New date to be determined Modeling liquid crystal elastomers: from auto-origami to responsive surfaces and a light-powered soft robot Liquid crystal elastomers combine the orientational order of liquid crystals with the elasticity of polymers. Remarkably, these materials flex and deform reversibly, driven by stimuli such as  illumination or heating, and can be programmed to morph from simple to complex shapes. The material’s liquid crystal director field, indicating the direction of molecular alignment, defines the local axis of induced contraction. We use GPU-based finite element elastodynamics modeling to study how patterns with director gradients and  topological defects give rise to complex actuation.  Continue reading… RESCHEDULED Robin Selinger (Kent State) Christoph Adami (Michigan State University) Wed. March 18th, 2020 4:30 pm-5:30 pm The importance of bias in the search for the origin of life The origin of life is a notoriously difficult subject, but assessing the likelihood of the spontaneous emergence of information is a mathematically tractable task. I show that the spontaneous emergence of sufficient information for life is impossible in a finite universe when assuming unbiased priors, but that biases that are reasonable in complex environments can significantly alter this likelihood, and move the process of spontaneous biogenesis into the realm of the possible. I mainly discuss the bias emerging from altered monomer probability distributions, but also present results from altered dimer frequencies. Continue reading… Christoph Adami (Michigan State University) CANCELLED or postponed: Sayak Dasgupta, Johns Hopkins University, Field theory of a hexagonal antiferromagnet with 3 sublattices Mon. March 16th, 2020 12:45 pm-1:45 pm Field theory of a hexagonal antiferromagnet with 3 sublattices Sayak Dasgupta, John’s Hopkins University, Department of Physics We present a classical field theory of magnetization dynamics in a generic 3-sublattice antiferromagnet in 2 spatial dimensions exemplified by the Heisenberg model on the triangular [1] and kagome [2] lattices. In a ground state, spins from the 3 sublattices are coplanar and at angles of 120° to one another such that S1+S2+S3=0. The six normal modes, shown in Fig. 1, either keep the spins in this plane (the a modes) or take them out of the plane (the b modes). Continue reading… CANCELLED or postponed: Sayak Dasgupta, Johns Hopkins University, Field theory of a hexagonal antiferromagnet with 3 sublattices Spring break, no seminar Mon. March 9th, 2020 1:00 am-1:00 am Continue reading… Spring break, no seminar Jagjit Singh Sidhu (CWRU) Tue. March 3rd, 2020 11:30 am-12:30 pm Charge Constraints of Macroscopic Dark Matter Macroscopic dark matter (macros) refers to a broad class of alternative candidates to particle dark matter with still unprobed regions of parameter space. Prior work on macros has considered elastic scattering to be the dominant energy transfer mechanism in deriving constraints on the abundance of macros for some range of masses and (geometric) cross-sections. However, macros with a significant amount of electric charge would, through Coulomb interactions, interact strongly enough to have produced observable signals on terrestrial, galactic and cosmological scales. We determine the expected phenomenological signals and constrain the corresponding regions of parameter space, Continue reading… Jagjit Singh Sidhu (CWRU) APS March meeting, no seminar Mon. March 2nd, 2020 1:00 am-1:00 am Continue reading… APS March meeting, no seminar APS March Meeting, No seminar Mon. March 2nd, 2020 1:00 am-1:00 am Continue reading… APS March Meeting, No seminar Susan Coppersmith (Wisconsin/New South Wales) Thu. February 27th, 2020 4:00 pm-5:00 pm Building a quantum computer using silicon quantum dots   The steady increase in computational power of information processors over the past half-century has led to smart phones and the internet, changing commerce and our social lives.  Up to now, the primary way that computational power has increased is that the electronic components have been made smaller and smaller, but within the next decade feature sizes are expected to reach the fundamental limits imposed by the size of atoms.  However, it is possible that further huge increases in computational power could be achieved by building quantum computers, which exploit in new ways of the laws of quantum mechanics that govern the physical world.   Continue reading… Susan Coppersmith (Wisconsin/New South Wales) Shruti Paranjape (University of Michigan) Tue. February 25th, 2020 11:30 am-12:30 pm Born-Infeld Theory Beyond the Leading Order The modern approach to scattering amplitudes exploits the symmetries of effective field theories. In this talk, I will focus on Born-Infeld, a theory of non-linear electrodynamics that has a myriad of interesting properties: It can be obtained as the “double copy” of Yang-Mills and chiral perturbation theory and it is the supersymmetric truncation of low-energy brane dynamics. Born-Infeld theory also has a classical electromagnetic duality symmetry. I will discuss how one can use these nice properties to uniquely fix all tree-level amplitudes in the theory. At subleading order, I will address one-loop amplitudes and admissible higher derivative corrections to the Born-Infeld effective field theory. Continue reading… Shruti Paranjape (University of Michigan) CWRU Physics grad students, APS March meeting talks preview Mon. February 24th, 2020 12:30 pm-2:00 pm List of speakers: not necessarily in that order, Please note earlier start at 12:30 pm and end at 2:00 pm ———————————- Kyle Crowley, Electrical Transport in Chemically Exfoliated LixCoO2 in 2D Nanoflake Form Brian Holler, 2D Semiconductor Transistors using Layered van der Waals Oxide MoO3 as High-K Gate Dielectric Arvind Shankar Kumar, Negative Parabolic Magneto-resistance in a strongly interacting 2D Hole system in GaAs/AlGaAs Mahdi Mehrnia, Fast, low-power defect-induced polarity switching of a magnetic vortex core Ruihao Li, Nonlinear Planar Hall as Another Signature of Chiral Anomaly in Weyl Semimetals Amol Ratnaparkhe, Continue reading… CWRU Physics grad students, APS March meeting talks preview Audrey Bienfait (ENS-Lyon) Michelson Postdoctoral Prize Lecture Fri. February 21st, 2020 12:45 pm-1:45 pm Microwave amplification at the quantum limit: implementing and operating a Josephson parametric amplifier A microwave electromagnetic field cooled down to millikelvin temperatures can reach its ground state: at this stage, all thermal fluctuations are suppressed and only quantum fluctuations remain. Reaching this regime enabled manipulation of the microwave fields at the single-photon level but also required the development of ultra-low-noise microwave amplifiers to ensure the detection of these quantum microwave states. Relying on non-dissipative parametric amplification using Josephson junctions, these Josephson parametric amplifiers (JPA) perform amplification while adding as little noise as allowed by quantum mechanics. Continue reading… Audrey Bienfait (ENS-Lyon) Michelson Postdoctoral Prize Lecture Audrey Bienfait (ENS-Lyon) Michelson Postdoctoral Prize Colloquium Thu. February 20th, 2020 4:00 pm-5:00 pm Interfacing quantum microwaves to spins and phonons Circuit quantum electrodynamics is a currently very active field of research. Since the discoveries that an artificial spin, the so-called qubit, can be implemented using a superconducting non-linear circuit and can coherently interact with the electromagnetic field at the single-photon level, it has gathered strong interest for its potential for quantum computing but also for its ability to create, manipulate and detect microwave states with an exquisite precision. In this talk, I will present how the tools and concepts developed for quantum circuits can be used to interface microwaves and phonons, Continue reading… Audrey Bienfait (ENS-Lyon) Michelson Postdoctoral Prize Colloquium Audrey Bienfait (ENS-Lyon) Michelson Postdoctoral Prize Lecture Wed. February 19th, 2020 12:45 pm-1:45 pm Magnetic resonance with quantum microwaves In usual magnetic resonance experiments, the coupling between spins and their electromagnetic environment is quite weak, severely limiting the sensitivity of the measurements and any interaction at the quantum level between spins and microwaves. In this lecture, I will show that using a Josephson parametric microwave amplifier combined with high-quality factor superconducting micro-resonators cooled at millikelvin temperatures enable the implementation of a magnetic resonance spectrometer where the detection sensitivity is limited by quantum fluctuations of the electromagnetic field instead of thermal or technical noise. The small mode volume superconducting microwave resonator also enhances the spin-resonator coupling up to the point where quantum fluctuations have an effect on the spin dynamics: The spin spontaneous emission of microwave photons in the resonator is dramatically enhanced by the Purcell effect, Continue reading… Audrey Bienfait (ENS-Lyon) Michelson Postdoctoral Prize Lecture Audrey Bienfait, (ENS-Lyon) Michelson Postdoctoral Prize Lecture Mon. February 17th, 2020 12:45 pm-1:45 pm Phonon-mediated quantum state transfer and remote entanglement Heavily used in classical signal processing, surface acoustic waves (SAWs) have also been proposed as a means to coherently couple distant solid-state quantum systems. Several groups have already reported the coherent coupling of standing SAWs modes to superconducting qubits, opening the door to the control and detection of quantum phonon states. In this lecture, I will explore the coherent coupling of superconducting qubits to propagating SAWs, demonstrating that quantum state transfer as well as remote entanglement generation between superconducting qubits using propagating SAWs can be realized. Continue reading… Audrey Bienfait, (ENS-Lyon) Michelson Postdoctoral Prize Lecture Paul Iversen (CWRU Classics) Thu. February 13th, 2020 4:00 pm-5:00 pm The Antikythera Mechanism: Discoveries Old & New The Antikythera Mechanism, so named after the Greek island in whose waters it was salvaged in 1901 from a shipwreck datable to ca. 70-60 BCE, is a remarkable geared device that was constructed in the 2nd or 1st century BCE to calculate and display various astronomical, calendrical and athletic time periods. No device of comparable technological complexity is known until 1,000 years later. In 2005, a group of researchers known as the Antikythera Mechanism Research Project (AMRP) examined the 82 fragments of this badly corroded and brittle device with two modern technologies called Micro-Focus X-Ray Computed Tomography (CT) and Polynomial Texture Mapping (PTM, Continue reading… Paul Iversen (CWRU Classics) Charlotte Sleight (IAS Princeton) Tue. February 11th, 2020 11:30 am-12:30 pm A Mellin Space Approach to Scattering in de Sitter Space Boundary correlators in (anti)-de Sitter space-times are notoriously difficult beasts to tame. In AdS, where such observables are equivalent to CFT correlation functions, recent years have seen significant progress in our understanding of their structure owing to the development of numerous systematic techniques, many of which have drawn inspiration from the successes and the strengths of the scattering amplitudes programme in flat space. In dS however, the problem is more complicated owing to the time-dependence of the background and it is unclear how consistent time evolution is encoded in spatial correlations on the boundary. Continue reading… Charlotte Sleight (IAS Princeton) Karsten Heeger (Yale University) Thu. February 6th, 2020 4:00 pm-5:00 pm The Quest to Understand Neutrino Mass Neutrinos play a central role in our understanding of the cosmos. From the observation of neutrino oscillation to the understanding of large-scale structure formation, massive neutrinos are a key ingredient to our understanding of the Universe at the smallest and largest scales. Recent experiments have precisely measured neutrino oscillation but fundamental questions about the nature and properties of neutrinos remain: Are neutrinos Majorana particles? What is the absolute mass of neutrinos, and why is it so small? Are there more than three neutrino species? In recent years, experiments measuring neutrinos from nuclear reactors and searching for rare nuclear decays have provided new insight to these questions. Continue reading… Karsten Heeger (Yale University) Jessica Winter (Ohio State University) Wed. February 5th, 2020 4:30 pm-5:30 pm Twenty Years Later: Why No Clinical Quantum Dot Imaging Labels? Quantum dots (QDs), semiconductor nanoparticles that fluoresce upon light excitation, were first introduced for biological imaging in 1998. At the time, QDs were heralded as a revolutionary product that would transform biological imaging. QDs have narrow emission bandwidths and broad excitation spectra, enabling multiplexed imaging. Their fluorescence is tunable based on QD size, permitting precise tuning of emission wavelength, and QDs are more resistant to photobleaching than their molecular dye counterpoints. Yet, despite 20 years of research, there are no clinically approved QD products and QDs remain a niche item used in specific research situations. Continue reading… Jessica Winter (Ohio State University) Craig Hogan (University of Chicago) Tue. February 4th, 2020 11:30 am-12:30 pm Holographic Inflation: Symmetries in the relic pattern of primordial perturbations from a coherent quantum inflationary horizon A reconciliation of quantum mechanics with gravity might be achieved in a holographic theory of quantum gravity, based on coherent states of covariant causal structures. This talk will review the properties of quantum-gravitational perturbations generated during cosmic holographic inflation, in which the inflationary horizon is a coherent quantum object, like the horizon of a black hole. A new analysis of cosmic anisotropy will be described, which shows evidence for some of the new symmetries. Continue reading… Craig Hogan (University of Chicago) Shane Parker, Dept. of Chemistry, Computational Photochemistry: Onwards with first-principles Mon. February 3rd, 2020 12:45 pm-1:45 pm Computational Photochemistry: Onwards with first-principles Shane Parker, Department of Chemistry, Case Western Reserve University   Photochemistry lies at the heart of chemical, biological, and technological processes, from photosynthesis to solar electricity generation. To harness the potential of light to drive new chemistry, a detailed understanding of the mechanisms of photochemical reactions is necessary. However, this is difficult to impossible to achieve based on experimental observations alone (often spectroscopy). I will introduce nonadiabatic molecular dynamics (NAMD) simulations using time-dependent density functional theory (TDDFT), an increasingly important framework that can unravel the atomistic details of photochemical reactivities. Continue reading… Shane Parker, Dept. of Chemistry, Computational Photochemistry: Onwards with first-principles The 2019 Nobel Prizes in Science Thu. January 30th, 2020 4:00 pm-5:00 pm Ben Monreal (Physics) on the prize in Physics, Dan Scherson (Chemistry) on the prize in Chemistry and Abhishek Chakraborty (Department of Cancer Biology) on the prize in Physiology or Medicine.  The 2019 Nobel Prize in Physics was awarded to Didier Queloz and Michel Mayor for their 1995 discovery of 51 Pegasi b, the first extrasolar planet.  The star 51 Pegasi is only a little different than the Sun, but 51 Pegasi b is like nothing previously known—it’s a Jupiter-like object, but in fiery hot orbit very close to the star.  Didier and Queloz, using a small telescope with an exquisite spectrograph, Continue reading… The 2019 Nobel Prizes in Science Matthew Digman (Ohio State University) Tue. January 28th, 2020 11:30 am-12:30 pm Not as big as a barn: Upper bounds on dark matter-nucleus cross sections Critical probes of dark matter come from tests of its elastic scattering with nuclei. The results are typically assumed to be model independent, meaning that the form of the potential need not be specified and that the cross sections on different nuclear targets can be simply related to the cross section on nucleons. For pointlike spin-independent scattering, the assumed scaling relation is σχA∝A2μ2AσχN∝A4σχN, where the A2 comes from coherence and the μ2A≃A2m2N from kinematics for mχ≫mA. Here we calculate where model independence ends, Continue reading… Matthew Digman (Ohio State University) Jukka Vayrynen, Microsoft Station Q, Santa Barbara , Signatures of topological ground state degeneracy in Majorana islands Mon. January 27th, 2020 12:45 pm-1:45 pm Title: Signatures of topological ground state degeneracy in Majorana islands Abstract: We consider a mesoscopic superconducting island hosting multiple pairs of Majorana zero-energy modes. The Majorana island consists of multiple p-wave wires connected together by a trivial (s-wave) superconducting backbone and is characterized by an overall charging energy $E_C$; the wires are coupled to normal-metal leads via tunnel junctions. Using a combination of analytical and numerical techniques we calculate the average charge on the island as well as non-local conductance matrix as a function of a p-wave pairing gap $\Delta_P$, charging energy $E_C$ and dimensionless junction conductances $g_i$. Continue reading… Jukka Vayrynen, Microsoft Station Q, Santa Barbara , Signatures of topological ground state degeneracy in Majorana islands Dan Styer (Oberlin College) Thu. January 23rd, 2020 4:00 pm-5:00 pm Entropy as Disorder: History of a Misconception  How did entropy morph from a quantifiable entity for finding the peak efficiency of a heat engine, into a synonym for “disorder”, and then into a catch-all name for anything bad?  Henry Adams (grandson of John Quincy Adams) plays a prominent role in this improbable story. Continue reading… Dan Styer (Oberlin College) Kevin Wood (University of Michigan) Wed. January 22nd, 2020 4:30 pm-5:30 pm Emergence and control in microbial communities:  steering bacterial pathogens through the phenotype space of multidrug resistance   Antibiotic resistance is a growing public health threat.  The emergence of resistance far outpaces the development of new drugs, underscoring the need for new strategies aimed at slowing the resistance threat.  In this talk, I’ll discuss our group’s ongoing work to understand the evolution of drug resistance in E. faecalis, an opportunistic bacterial pathogen, using quantitative experiments and theoretical tools from statistical physics and dynamical systems. By combining laboratory evolution with simple mathematical models, we show that unconventional strategies–including aperiodic drug dosing, Continue reading… Kevin Wood (University of Michigan) MLK Jr holiday, no seminar Mon. January 20th, 2020 1:00 am-1:00 am Continue reading… MLK Jr holiday, no seminar Adi Nusser (Technion) Tue. January 14th, 2020 11:30 am-12:30 pm New and old probes of the structure of the evolved Universe The observed large scale distribution of galaxies and their peculiar motions (on top of the pure Hubble flow) are very well described in the framework of the standard Lambda Cold Dark Matter model. The model is founded on general relativity (GR) which in itself has recently gained substantial support by the detection of gravitational waves. Despite this success, observational data on large scales allow for deviations from the GR and the standard model. Any tiny deviation may have profound implications on fundamental physical theory of the Universe. Continue reading… Adi Nusser (Technion) Bira van Kolck (Institut de Physique Nucleaire d’Orsay and University of Arizona) Tue. December 10th, 2019 11:30 am-12:30 pm A New Leading Mechanism for Neutrinoless Double-Beta Decay … or how to attract the ire of the community. The neutrinoless double-beta decay of nuclei is essentially the only way to test lepton-number violation coming from the possible Majorana character of neutrinos. Tremendous effort is dedicated to its measurement and to reducing the theoretical uncertainty in the calculation of the nuclear matrix elements needed for its interpretation. Well, we increase the uncertainty. Continue reading… Bira van Kolck (Institut de Physique Nucleaire d’Orsay and University of Arizona) (CANCELED) Alexander Govorov, Ohio University, Plasmonic Bio-Assemblies and Metastructures: Chirality, Coherent Transfer of Plasmons and Generation of Hot Electrons Mon. December 9th, 2019 12:45 pm-1:45 pm CANCELED Plasmonic Bio-Assemblies and Metastructures: Chirality, Coherent Transfer of Plasmons and Generation of Hot Electrons  Alexander O. Govorov Department of Physics and Astronomy, Ohio University, Athens, USA; govorov@ohio.edu Plasmonic nanostructures and metamaterials are very efficient at absorption and scattering of light. The studies to be presented in this talk concern special designs of hybrid nanostructures with electromagnetic hot spots, where the electromagnetic field becomes strongly enhanced and spatially concentrated. Overall, plasmonic nanostructures with hot spots demonstrate strongly amplified optical and energy-related effects, Continue reading… (CANCELED) Alexander Govorov, Ohio University, Plasmonic Bio-Assemblies and Metastructures: Chirality, Coherent Transfer of Plasmons and Generation of Hot Electrons Roman Scoccimarro (NYU) Tue. November 26th, 2019 11:30 am-12:30 pm Bispectrum Bias Loops and Power Spectrum Covariance I will discuss recent progress in two topics in large-scale structure: 1) understanding galaxy bias beyond leading order in perturbation theory and its application to the bispectrum, and 2) how to model the covariance of the galaxy power spectrum multipoles analytically instead of using numerical simulations. Continue reading… Roman Scoccimarro (NYU) Luke Bissell, AFRL, Solid State Materials Strategies for Quantum Information Mon. November 25th, 2019 12:45 pm-1:45 pm Solid State Materials Strategies for Quantum Information Luke Bissell, Air Force Research Laboratory In this talk I will first discuss the Air Force Research Laboratory (AFRL) strategy for investment in quantum information research, highlighting activities in the Information (Rome, NY), Space Vehicles and Directed Energy (Albuquerque, NM) and Materials and Manufacturing and Sensors Directorates (Dayton, OH). In the near term, AFRL is pursuing quantum sensing technologies for improved timekeeping and navigation in GPS denied environments. Mid-term investments are focused in architectures for quantum networks, including the entangled photon sources and quantum memories needed to realize them. Continue reading… Luke Bissell, AFRL, Solid State Materials Strategies for Quantum Information Raymond Brock (Michigan State University) Thu. November 21st, 2019 4:00 pm-5:00 pm That Spin Zero Boson Changes Everything: The Future of the Energy Frontier in Particle Physics The “Higgs Boson” discovery requires us to think differently about planning for the future of Particle Physics. While the decades-long confirmation of the Standard Model itself is an historic episode – as a dynamical model of nature, it is not helpful as a clear guide to the future. I will l review the features of the Standard Model that make it superb, but also  point out why it’s frustrating, and I’ll describe the hints that motivate us for the coming decades. Continue reading… Raymond Brock (Michigan State University) Garrett Goon (CMU) Tue. November 19th, 2019 11:30 am-12:30 pm Linking Corrections to Entropy and Extremality I will prove that the leading perturbative corrections to the entropy and extremality bounds of black holes are directly proportional to each other, generically.  This fact is intimately related to the Weak Gravity Conjecture, as I will discuss. The proof is purely thermodynamic and applies to systems beyond the gravitational realm. Continue reading… Garrett Goon (CMU) Jesse Thaler (MIT) Fri. November 15th, 2019 12:45 pm-1:45 pm Quantum Algorithms for Collider Physics As particle physics experiments continue to stretch the limits of classical computation, it is natural to ask about the potential future role of quantum computers.  In this talk, I discuss the potential relevance of quantum algorithms for collider physics.  I present a proof-of-concept study for “thrust”, a well-known collider observable that has O(N^3) runtime for a collision involving N final-state particles.  Thrust is a particularly interesting observable in this context, since it has two dual formulations, one which naturally maps to quantum annealing and one which naturally maps to Grover search.  Continue reading… Jesse Thaler (MIT) Jesse Thaler (MIT) Thu. November 14th, 2019 4:00 pm-5:00 pm Particle Physics meets Machine Learning Modern machine learning has had an outsized impact on many scientific fields, and particle physics is no exception.  What is special about particle physics, though, is the vast amount of theoretical and experimental knowledge that we already have about many problems in the field.  In this colloquium, I present two cases studies involving quantum chromodynamics (QCD) at the Large Hadron Collider (LHC), highlighting the fascinating interplay between theoretical principles and machine learning strategies.  First, by cataloging the space of all possible QCD measurements, we (re)discovered technology relevant for self-driving cars.  Second, Continue reading… Jesse Thaler (MIT) Daniel Beller, University of California Merced, Topological defect structure and dynamics in 3D active nematics Mon. November 11th, 2019 12:45 pm-1:45 pm Topological defect structure and dynamics in 3D active nematics Nematic liquid crystals, which are fluids with orientational order, may contain topological defects called disclinations where this order breaks down. While they’re undesirable in LCD screens, disclinations play an essential role in the dynamics of active nematics, non-equilibrium systems with internally driven flows coupled to nematic orientational distortions. Examples include cytoskeletal biofilaments with molecular motors, bacterial colonies, and some eukaryotic cellular tissues. In quasi-2D confinement, disclinations are point-like, and their pair-unbinding and motility drives the chaotic dynamics. In this talk, I will explore how the situation in 3D is even more complex. Continue reading… Daniel Beller, University of California Merced, Topological defect structure and dynamics in 3D active nematics Lisa Lapidus (Michigan State Univ) Thu. November 7th, 2019 4:00 pm-5:00 pm Protein monomer dynamics control the first steps of aggregation and disease Many neurodegenerative diseases, such as Parkinson’s and Alzheimer’s, are caused by uncontrolled aggregation of proteins.  While many aggregation-prone proteins ultimately form fibrillary structures, evidence suggests that early, unstructured aggregates are toxic to neurons.  The complexity and dynamics of unfolded protein ensembles may be the ultimate speed limit of folding and play a crucial role in aggregation. In my lab over the past several years we have investigated the reconfiguration dynamics of unfolded proteins by measuring the rate of intramolecular diffusion, the rate one part of the chain diffuses relative to another.  Continue reading… Lisa Lapidus (Michigan State Univ) Clara Murgui (IFIC, Valencia) Tue. November 5th, 2019 11:30 am-12:30 pm The QCD Axion and Unification The QCD axion is one of the most appealing candidates for the dark matter in the Universe. In this article, we discuss the possibility to predict the axion mass in the context of a simple renormalizable grand unified theory where the Peccei-Quinn scale is determined by the unification scale. In this framework, the axion mass is predicted to be in the range ma ≃ (3 − 13) × 10−9 eV. We study the axion phenomenology and find that the ABRACADABRA and CASPEr-Electric experiments will be able to fully probe this mass window. Continue reading… Clara Murgui (IFIC, Valencia) Mikel Holcomb, West Virginia University, Collaborative efforts in materials physics Mon. November 4th, 2019 12:45 pm-1:45 pm Collaborative efforts in materials physics Due to the collaborative nature of the Holcomb group’s expertise, we explore many significant areas in materials science, including magnetism, magnetoelectricity, topological insulators and other quantum systems. This talk will focus on primarily our beamline efforts, as these often provide the most meaningful results. I will provide a few example cases and discuss our latest discovery of a new form of magnetism.   Host: Jesse Berezovsky Continue reading… Mikel Holcomb, West Virginia University, Collaborative efforts in materials physics Alexandra Boltasseva (Purdue) Machine-Learning-Assisted Photonics: From Optimized Design to Quantum Measurements Thu. October 31st, 2019 4:00 pm-5:00 pm Emerging photonic concepts such as optical metamaterials, metasurfaces, novel lasers, single-photon sources and other quantum photonic devices together with novel optical material platforms promise to bring revolutionary advances to information processing and storage, communication systems, energy conversion, imaging, sensing and quantum information technology. In pursuit of the next generation of photonic technologies, machine learning approaches have emerged as a powerful tool to discover unconventional optical designs and even uncover new optical phenomena. In this talk, various photonic design approaches as well as emerging material platforms will be discussed showcasting machine-learning-assisted topology optimization for efficient thermophotovoltaic metasurface designs as well as machine-learning enabled quantum optical measurements. Continue reading… Alexandra Boltasseva (Purdue) Machine-Learning-Assisted Photonics: From Optimized Design to Quantum Measurements Juri Smirnov (Ohio State University) Tue. October 29th, 2019 11:30 am-12:30 pm Dark Matter Research with Bound Systems   My discussion will rest on three pillars. The first is an overview of bound states in dark sectors, and their implications for dark matter phenomenology, mass predictions and dark matter model building. The second is an exploration of new experimental techniques, which are needed to search for dark matter, which resides in a sector containing bound states. Finally, I will discuss some experimental observations based on bound states of ordinary matter, which can be used to constrain some of the introduced dark matter scenarios. Continue reading… Juri Smirnov (Ohio State University) Alexey Kovalev, University of Nebraska Lincoln, Nonequilibrium spin currents and spin polarization in noncollinear antiferromagnetic insulators Mon. October 28th, 2019 12:45 pm-1:45 pm Nonequilibrium spin currents and spin polarization in noncollinear antiferromagnetic insulators Alexey Kovalev, Department of Physics, University of Nebraska, Lincoln An ability to control spin is important for probing many spin related phenomena in the field of spintronics. Spin-orbit torque is an important example in which spin flows across magnetic interface and helps to control magnetization dynamics. As spin can be carried by electrons, spin-triplet pairs, Bogoliubov quasiparticles, magnons, spin superfluids, spinons, etc., studies of spin currents can have implications across many disciplines. In this talk, I first review the most common ways to generate spin flows and then concentrate on how spin can be controlled via magnons in insulating materials. Continue reading… Alexey Kovalev, University of Nebraska Lincoln, Nonequilibrium spin currents and spin polarization in noncollinear antiferromagnetic insulators ***POSTPONED*** Raymond Brock (Michigan State Univ) Thu. October 24th, 2019 4:00 pm-5:00 pm ***POSTPONED*** That Spin Zero Boson Changes Everything: The Future of the Energy Frontier in Particle Physics The “Higgs Boson” discovery requires us to think differently about planning for the future of Particle Physics. While the decades-long confirmation of the Standard Model itself is an historic episode – as a dynamical model of nature, it is not helpful as a clear guide to the future. I will l review the features of the Standard Model that make it superb, but also  point out why it’s frustrating, and I’ll describe the hints that motivate us for the coming decades. Continue reading… ***POSTPONED*** Raymond Brock (Michigan State Univ) Mathias Schubert, University of Nebraska-Lincoln, Phonons, free charge carriers, excitons and band-to-band transitions in beta Ga2O3 and related alloys determined by ellipsometry and optical Hall effect Mon. October 21st, 2019 12:45 pm-1:45 pm Phonons, free charge carriers, excitons and band-to-band transitions in beta Ga2O3 and related alloys determined by ellipsometry and optical Hall effect Schubert1,2,3, A. Mock4, S. Knight1, M. Hilfiker1, M. Stokey1, V. Darakchieva2, A. Papamichail2, R. Korlacki1, M.J. Tadjer5, Z. Galazka6, G. Wagner6, N. Blumenschein7, A. Kuramata8, K. Goto8,9, H. Murakami9, Y. Kumagai8, M. Higashiwaki10, A. Mauze11, Y. Zhang11, J. S. Speck11   1Department of Electrical and Computer Engineering, University of Nebraska – Lincoln, Nebraska 68588, USA 2Department of Physics, Chemistry and Biology (IFM), Linkoping University, SE 58183 Linkoping, Sweden 3Leibniz Institute for Polymer Research, Continue reading… Mathias Schubert, University of Nebraska-Lincoln, Phonons, free charge carriers, excitons and band-to-band transitions in beta Ga2O3 and related alloys determined by ellipsometry and optical Hall effect Nick Abbott (Biomolecular Engineering, Cornell) Thu. October 17th, 2019 4:00 pm-5:00 pm EQUILIBRIUM AND NON-EQUILIBRIUM INTERFACIAL STATES OF LIQUID CRYSTALS IN CONTACT WITH BIOLOGICAL SYSTEMS The generation, management and transduction of dynamic mechanical forces is one of the central sciences of living biological systems.  The development of synthetic soft matter that can exchange mechanical information with bacterial and mammalian cells has the potential to yield new classes of hybrid material systems that can report on and direct living biological systems.  This presentation will explore mechanical interactions of synthetic liquid crystalline materials and living systems in the context of molecular assemblies and cells.  The examples discussed in this presentation will illustrate how both equilibrium and non-equilibrium interfacial states of liquid crystals can give rise to new classes of functional soft materials that pass mechanical, Continue reading… Nick Abbott (Biomolecular Engineering, Cornell) Chi Tian (CWRU) Tue. October 15th, 2019 11:30 am-12:30 pm Black-Hole Lattices as Cosmological Models Challenges for modern cosmology include determining the influence the small-scale structure has in the universe on its large-scale dynamics and observations. With numerical relativity tools, finding and exploring cosmological models which are exact solutions to the Einstein equations will resolve all the non-linearities so that give us hints on quantifying the influence. In this talk, I will introduce Black-Hole Lattice models, which are subsets of relativistic discrete cosmological models. In particular, I will start from constructing those spacetimes and show what we can learn from exploring their properties. Continue reading… Chi Tian (CWRU) No seminar faculty meeting Mon. October 14th, 2019 12:45 pm-1:45 pm Continue reading… No seminar faculty meeting Michael Poirier (Ohio State University) Thu. October 10th, 2019 4:00 pm-5:00 pm The Physics of the Human Genome Each of our cells contain 1 meter of DNA that is tightly wrapped to fit inside the ~5 micron wide nucleus of the cell. This highly condensed state of our DNA plays a central role in how the information in our genes is replicated, read and repaired. Yet, the physical mechanics by which genome organization regulates the processing of DNA remains a mystery. I will review what is currently understood about genomic organization with a focus on the first level of organization, the nucleosome – a 50 nm stretch of DNA tightly wrapped ~2 times around a protein core. Continue reading… Michael Poirier (Ohio State University) Cedric Weiland (University of Pittsburgh) Tue. October 8th, 2019 11:30 am-12:30 pm Electroweak measurements at electron-positron colliders as indirect searches for heavy neutrinos Heavy neutrinos are part of many extensions of the Standard Model, in particular seesaw models that can explain the light neutrino masses and mixing. Future electron-positron colliders would greatly increase the precision of the measurements of electroweak processes. I will discuss how this improved precision offers new opportunities to search for the effects of heavy neutrinos. In particular, I will focus on indirect search strategies based on the modifications of the production cross-sections of W or Higgs bosons at linear collider. These searches are complementary to other observables and would allow to probe the multi-TeV mass regime at future colliders. Continue reading… Cedric Weiland (University of Pittsburgh) Andrew Cleland (U Chicago) Thu. October 3rd, 2019 4:00 pm-5:00 pm Quantum control of acoustic phonons Superconducting qubits provide an excellent approach to building quantum computing systems, due to their good performance metrics and their easy lithographic scaling to large qubit numbers. In addition, these qubits provide unique opportunities as testbed systems for quantum communication as well as developing hybrid quantum systems. Here, I will discuss applications for superconducting qubits in generating and detecting individual phonons, in the form of quantum surface acoustic wave (SAW) excitations, and using these phonon states to generate remote quantum entanglement. Specifically, I will describe recent experiments [1,2] where we have demonstrated the use of reasonably high finesse acoustic Fabry-Perot structures to store acoustic phonon Fock states, Continue reading… Andrew Cleland (U Chicago) Gilles Gerbier (Queen’s U) Tue. October 1st, 2019 11:30 am-12:30 pm Searching for low mass dark matter particles at SNOLAB 90 years after its first evidence by F Zwicky, the nature of the dark matter of the Universe  is still unknown. There is a consensus it should be made of elementary particles but their search has been going on for several decades without success. Huge progress in sensitivity has been done, though,  thanks to new innovative detection techniques. Indeed some new techniques allow to enlarge the exploration of parameter space.  I will describe status of two projects I have developed, within international collaborations, thanks to a CERC grant in Canada, Continue reading… Gilles Gerbier (Queen’s U) Guang Bian, University of Missouri, Symmetry-Enforced Dirac Fermions in Nonsymmorphic α-Bismuthene Mon. September 30th, 2019 12:45 pm-1:45 pm Symmetry-Enforced Dirac Fermions in Nonsymmorphic α-Bismuthene    Guang Bian, Department of Physics and Astronomy, University of Missouri   The discovery of graphene and topological insulators has stimulated enormous interest in two-dimensional electron gases with linear band dispersion. The vanishing effective mass and non-zero Berry phase of Dirac fermion-like states give rise to many remarkable physical properties such as extremely high mobility and zero-energy Landau levels. According to recent theoretical works, nonsymmorphic crystal symmetries can enforce the formation of Dirac cones, providing a new route to establishing Dirac states in 2D materials.  Here we will discuss our recent work on the realization of the symmetry-enforced Dirac fermions in nonsymmorphic α-bismuthene (Bi monolayer). Continue reading… Guang Bian, University of Missouri, Symmetry-Enforced Dirac Fermions in Nonsymmorphic α-Bismuthene Thijs Heus (Cleveland State University) Thu. September 26th, 2019 4:00 pm-5:00 pm Organization of clouds, and their impact on the climate system Clouds are some of the largest uncertainties in weather and climate forecasting. They are also an interesting physical phenomenon, and despite having been studied and admired for millennia, there is still a lot that we do not understand, thanks to the multitude of physical processes. In the atmospheric system, clouds serve as a key component of a heat engine. The solar/infrared radiative fingerprint of clouds depends strongly on the droplet size distribution: Smaller droplets will result in a larger reflectivity, but also alters cloud lifetime. These effects are further complicated by organization and clustering of cloud fields. Continue reading… Thijs Heus (Cleveland State University) Laura Johnson (CWRU) Tue. September 24th, 2019 11:30 am-12:30 pm Massive Gravitons in Curved Spacetimes This talk will cover various interesting topics that occur in massive spin-2 on various spacetimes including de Sitter, anti-de Sitter, and flat space. In de Sitter, we examine what happens to massive gravity as its mass approaches the partially massless value. In this limit, if the interactions are chosen to be precisely those of the ’candidate’ non-linear partially massless theory, the strong coupling scale is raised, giving the theory a wider range of applicability. In anti-de Sitter and flat spacetime, we show how shift symmetries acting on the vector modes emerge from massive spin-2 theories fixing the non-linear structure and discuss whether these theories have amplitudes that can be constructed via soft substracted recursion. Continue reading… Laura Johnson (CWRU) Antia Botana, Arizona State University, Mimicking cuprates with low-valence layered nickelates. Mon. September 23rd, 2019 12:45 pm-1:45 pm Mimicking cuprates with low-valence layered nickelates. Antia Botana, Dept. of Physics, Arizona State University, Tempe, AZ The physics behind high-temperature superconducting cuprates remains a defining problem in Condensed Matter Physics. One way of addressing this problem has been to search for alternative transition metal oxides with comparable structures and 3d electron count, proxies for cuprate physics. By means of electronic structure calculations, we propose low-valence layered nickelates as one of the closest analogs to cuprates yet reported. These materials possess a combination of traits that are widely considered as crucial ingredients for high-temperature superconductivity in cuprates: a square-planar nature, Continue reading… Antia Botana, Arizona State University, Mimicking cuprates with low-valence layered nickelates. Goran Senjanovic (ICTP, Trieste) Fri. September 20th, 2019 12:45 pm-1:45 pm The fall and rise of parity and the origin of (neutrino) mass Continue reading… Goran Senjanovic (ICTP, Trieste) Goran Senjanovic (ICTP) Thu. September 19th, 2019 4:00 pm-5:00 pm Neutrino: chronicles of an aloof witness As you read this, trillions of neutrinos from the sun are passing through every square cm of your body, doing no harm whatsoever. They convey information from the depth of the universe and have been present from its very birth. Neutrinos have captured the imagination of physicists from the time they were first conceived and have repeatedly provided a window into new physics. A question stood out for decades: Are neutrinos massive like their seemingly inseparable electron siblings? It took almost seventy years to obtain the positive answer. Continue reading… Goran Senjanovic (ICTP) Goran Senjanovic (ICTP, Trieste) Wed. September 18th, 2019 1:30 pm-2:30 pm Strong CP violation: fancy and fact Continue reading… Goran Senjanovic (ICTP, Trieste) Jixin Chen, Ohio University Mon. September 16th, 2019 12:45 pm-1:45 pm Photophysics as a Tool to Measure the Surface-State of Perovskite Nanoparticles Jixin Chen, Department of Physics, Ohio University The photoluminescence (PL) of organolead halide perovskites (OHPs) is sensitive to OHPs’ surface conditions and an effective way to report surface states. OHP is a hot semiconducting material that has a large potential in solar cells and LEDs. Photophysics describes the light-matter interactions in the materials using several phenomena such as absorption, exciton relaxation, emission quantum yield, photoblinking, and photodarkening/photobleaching. In this seminar, Dr. Chen will focus his talk on the photoblinking and photodarkening of perovskite nanoparticles. Continue reading… Jixin Chen, Ohio University Christine Duval (Chem Engineering, CWRU) Thu. September 12th, 2019 4:00 pm-5:00 pm Countering Weapons of Mass Destruction with Advanced Separations Illicit nuclear activities such as the assembly of weapons of mass destruction or radiological dispersal devices (“dirty bombs”) pose a threat to national and world security.  National governments and world-wide organizations such as the International Atomic Energy Agency share an interest in monitoring and regulating international nuclear processes and materials. Nuclear forensics involves the examination of radioactive materials, using a variety of analytical techniques, with an end goal of determining the history and origin of the substance—guiding law-enforcement agencies as they determine “Whodunnit?”  This talk will introduce the role of scientists in nuclear forensics and identify technological needs for fieldable radiation detection techniques. Continue reading… Christine Duval (Chem Engineering, CWRU) Callum Jones (University of Michigan) Tue. September 10th, 2019 11:30 am-12:30 pm Born-Infeld Electrodynamics at One-Loop The Born-Infeld model is an effective field theory of central importance describing the low-energy dynamics of massless gauge bosons on the world-volume of D-branes. Though it is in many ways exceptional in the universality class of models of nonlinear electrodynamics, several aspects of the physics of the Born-Infeld model remain mysterious. In this talk I will explain how aspects of the model, obscured in the traditional formulation of Lagrangian field theory, are clarified by directly studying the on-shell S-matrix. In particular in 3+1-dimensions, classical Born-Infeld has an electromagnetic duality symmetry which manifests in tree-level scattering amplitudes as the conservation of a chiral charge. Continue reading… Callum Jones (University of Michigan) Joshua Goldberger, The Ohio State University, Axis-dependent conduction polarity in layered materials Mon. September 9th, 2019 12:45 pm-1:45 pm Axis-dependent conduction polarity in layered materials  Department of Chemistry and Biochemistry, The Ohio State University, Columbus Layered and two-dimensional materials have emerged as one of the most exciting families of solid-state compounds, due to the plethora of unique physical phenomena found in these materials coupled with advances in the characterization of structure and properties down to the single layer scale. Here, we will describe our efforts in developing new families of these compounds, and our recent discovery of axis-dependent conduction polarity these materials.  Electronic materials generally exhibit a single majority carrier type, electrons or holes.  Continue reading… Joshua Goldberger, The Ohio State University, Axis-dependent conduction polarity in layered materials Erin Blauvelt (Lehigh University) Mon. September 9th, 2019 3:15 pm-4:15 pm Striped and Superconducting Phases in Holography There is a duality out of the framework of string theory that tells us, in certain cases, gravity can be thought of as emerging from the quantum mechanical degrees of freedom of a system. Remarkably, this relationship has not only given us a long sought after microscopic description of black holes and insights into the fabric of spacetime, but has also proven itself useful as a novel analytic toolset to investigate non-perturbative systems. Known as holography, this weak/strong coupling duality allows us to examine strongly coupled quantum systems by mapping them to perturbative,  Continue reading… Erin Blauvelt (Lehigh University) Bharat Ratra (Kansas State University) Fri. September 6th, 2019 11:30 am-12:30 pm Cosmological Seed Magnetic Field from Inflation A cosmological magnetic field of nG strength on Mpc length scales could be the seed magnetic field needed to explain observed few microG large-scale galactic magnetic fields. I first briefly review the observational and theoretical motivations for such a seed field, two galactic magnetic field amplification models, and some non-inflationary seed field generation scenarios. I then discuss an inflation magnetic field generation model. I conclude by mentioning possible extensions of this model as well as potentially observable consequences. Continue reading… Bharat Ratra (Kansas State University) Bharat Ratra (Kansas State University) Thu. September 5th, 2019 4:00 pm-5:00 pm 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. Continue reading… Bharat Ratra (Kansas State University) Jacob Seiler (Swinburne University of Technology, Melbourne) Tue. May 7th, 2019 11:30 am-12:30 pm Coupling Galaxy Evolution and the Epoch of Reionization The Epoch of Reionization is a pivotal period in our cosmic history, representing the transition from a neutral post-recombination Universe into the fully ionized one we observe today. The procession of reionization is dictated by the fraction of ionizing photons, fesc, that escapes from galaxies to ionize the inter-galactic medium, with the exact value and functional form still an open question. I explore this question using the Semi-Analytic Galaxy Evolution (SAGE) model to generate galaxy properties, such as the number of ionizing photons emitted, and follow different possible Epoch of Reionization scenarios with a semi-numerical scheme. Continue reading… Jacob Seiler (Swinburne University of Technology, Melbourne) Sinead Griffin (Lawrence Berkeley Lab) Thu. April 25th, 2019 4:00 pm-5:00 pm What Crystals Can Tell Us About the Origins of the Universe Jumping from studying galactic scales to the nanoscale crystals in the laboratory might seem a gargantuan task. Common to both, however, is the concept of symmetry breaking and in particular the formation of topological defects – the materials equivalent of cosmic strings – in multiferroic crystals whose ferroelectric behavior enables the direct imaging of these defects. I also show how these crystals can be used to study an early-universe theory – the Kibble Zurek model – in the lab and demonstrate its verification for the first time in a crystal. Continue reading… Sinead Griffin (Lawrence Berkeley Lab) Aldo Romero, West Virginia University, Designing materials: a synergistic process between theory, experiment and belief Mon. April 22nd, 2019 12:45 am-1:45 am Designing materials: a synergistic process between theory, experiment and belief Aldo Romero, Dept. of Physics and Atronomy, West Virginia University, Morgantown The scientific process of designing materials has changed in the last ten years, as now theoretical methods have advanced to the level of becoming predictive, materials databases are increasing in size and experiments are more accurate and detailed. In this synergistic path, methods that combine all these methodologies are ideal, as long as we manage to condense the necessary design details into a series of fundamental material parameters. In this talk, I will discuss the atomistic process to design materials from scratch by using theoretical methods only based on the chemical composition and with little knowledge on the desired material or property of interest. Continue reading… Aldo Romero, West Virginia University, Designing materials: a synergistic process between theory, experiment and belief Allan MacDonald (U Texas Austin), Moiré Patterns   in Two-Dimensional Materials Thu. April 18th, 2019 4:00 pm-5:00 pm Moiré Patterns   in Two-Dimensional Materials According to Wikipedia a moiré pattern (/mwɑːrˈeɪ/; French: [mwaˈʁe]) is a large scale interference pattern that is produced when an opaque regular pattern with transparent gaps is overlaid on another similar pattern with a different pitch or orientation.  Moiré patterns are ubiquitous in two-dimensional van der Waals materials in which the regular patterns are formed by two-dimensional crystals, differences in pitch are established by differences in lattice constants and differences in orientation, which can be controlled experimentally.  The electronic properties of two-dimensional semiconductor, Continue reading… Allan MacDonald (U Texas Austin), Moiré Patterns   in Two-Dimensional Materials Yue Zhang (Fermilab) Tue. April 16th, 2019 11:30 am-12:30 pm Electroweak Baryogenesis, ACME II, and Dark Sector CP Violation   The origin of the matter-anti-matter asymmetry in the universe is a big puzzle for particle physics and cosmology. Baryogenesis mechanisms at the electroweak scale are attractive for their testability at high-energy colliders and low-energy experiments. The recent measurement of electron electric dipole moment by ACME II sets stringent limit on weak scale CP violations and challenges the viable parameter space for successful electroweak baryogenesis in traditional models, such as two-Higgs doublet models and supersymmetry. In this talk, I will present our recent proposal of triggering electroweak baryogenesis with dark sector CP violation, Continue reading… Yue Zhang (Fermilab) Horacio Castillo, Ohio University, Strong fluctuations in the relaxation of a 2D granular fluid Mon. April 15th, 2019 12:45 am-1:45 am Strong fluctuations in the relaxation of a 2D granular fluid Horacio Castillo, Department of Physics and Astronomy, Ohio University Glass transitions are associated with a rapid increase of the relaxation time in a system as a function of an external parameter, usually temperature or volume fraction. In the regime near the glass transition, materials exhibit “dynamical heterogeneity”, i.e., the presence of correlated fluctuations in the dynamical behavior of small regions of the system, whose origin is still poorly understood. I will discuss the results of large-scale numerical simulations of a two dimensional granular fluid, Continue reading… Horacio Castillo, Ohio University, Strong fluctuations in the relaxation of a 2D granular fluid The 2018 Nobel Prizes in Science: What were they given for? Thu. April 11th, 2019 4:00 pm-5:00 pm Cosponsored by the Cell Biology Program and the Departments of Chemistry and Physics 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, Continue reading… The 2018 Nobel Prizes in Science: What were they given for? James Wells (University of Michigan-Ann Arbor) Tue. April 9th, 2019 11:30 am-12:30 pm Unification and Precision Measurements   Abstract: The Standard Model of particle physics may yet be unified into a deeper organizing principle. The gauge groups may unify into higher rank gauge group, and the Yukawa couplings might unify into a simplifying symmetry group. The key to assessing these unification prospects is precision measurements and related precision theory. The current status of unification, in its various guises, is discussed from the perspective of precision analysis. In addition, the prospects for further stress-testing the ideas at future experiment and through future theory work are also presented. Continue reading… James Wells (University of Michigan-Ann Arbor) Vladimir Dobrosavljevic, Florida State University, Geometrically Frustrated Coulomb Liquids Mon. April 8th, 2019 12:45 pm-1:45 pm Geometrically Frustrated Coulomb Liquids V. Dobrosavljevic Department of Physics and National High Magnetic Field Laboratory Florida State University, Tallahassee, Florida 32306, USA We show[1] that introducing long-range Coulomb interactions immediately lifts the massive ground state degeneracy induced by geometric frustration for electrons on quarter-filled triangular lattices in the classical limit. Important consequences include the stabilization of a stripe-ordered crystalline (global) ground state, but also the emergence of very many lowlying metastable states with amorphous “stripe-glass” spatial structures[2]. Melting of the stripe order thus leads to a frustrated Coulomb liquid at intermediate temperatures, Continue reading… Vladimir Dobrosavljevic, Florida State University, Geometrically Frustrated Coulomb Liquids Matthew Fisher (KITP Santa Barbara) Thu. April 4th, 2019 4:00 pm-5:00 pm Quantum Processing in the Brain? Building a laboratory quantum computer is now a billion dollar enterprise. But might we, ourselves, be quantum computers? While maintaining quantum coherence on macroscopic time scales is exceedingly unlikely in the warm wet brain, there is one exception: Nuclear spins. My strategy is one of reverse engineering, seeking to identify the biochemical substrate and mechanisms that could host such putative nuclear spin quantum processing. Remarkably, a specific neural qubit and a unique collection of ions, molecules and enzymes can be identified, illuminating an apparently single path towards quantum processing in the brain. Continue reading… Matthew Fisher (KITP Santa Barbara) Maura McLaughlin (West Virginia University) Tue. April 2nd, 2019 11:30 am-12:30 pm The NANOGrav 11-year Data Set: New Insights into Galaxy Growth and Evolution Ira Rothstein (Carnegie Mellon University) Thu. March 28th, 2019 4:00 pm-5:00 pm Precision Gravitational Astronomy   Abstract:    The monumental measurement of gravity waves at LIGO has ushered in a new field of science with wide ranging implications, from Astrophysics and Cosmology to Nuclear Physics, Particle Physics and, of  course, General Relativity. However, our ability to extract information from the signal is bounded by our theoretical power. In this talk I will discuss how Effective Field Theory  techniques have been used to generate the highest precision analytic results for the signals generated by inspiraling binaries, emphasizing phenomenological benchmarks. I will also show how space-time geometry is actually encoded in gravitational S-matrix elements such that we may calculate forces between black holes with high precision using modern scattering amplitude techniques. Continue reading… Ira Rothstein (Carnegie Mellon University) Subir Sachdev (Harvard University) Thu. March 21st, 2019 4:00 pm-5:00 pm Strange metals and black holes The  ‘strange metal’, a state of matter formed by electrons in many modern materials, including the compounds which exhibit high temperature superconductivity. In this state, electrons quantum entangle with each other and conduct electric current collectively (rather than one-by-one, as in an ordinary metal like copper).  Quantum entanglement also has remarkable effects near the horizon of a black hole, leading to the Bekenstein-Hawking black hole entropy, and the Hawking temperature. Surprisingly, there is a deep connection between the nature of quantum entanglement in strange metals and black holes, and this has led to mutually beneficial insights.  Continue reading… Subir Sachdev (Harvard University) Benjamin Monreal (CWRU) Tue. March 19th, 2019 11:30 am-12:30 pm Giant telescopes, exoplanets, and astronomy in the 2020s Shixiong Zhang, Indiana University, Controlled Synthesis and Emergent Properties of Heavy Transition Metal Oxides and Sulfides Mon. March 18th, 2019 12:45 pm-1:45 pm Controlled Synthesis and Emergent Properties of Heavy Transition Metal Oxides and Sulfides Shixiong Zhang Department of Physics, Indiana University, Bloomington, IN, USA Heavy transition metal compounds (e.g. oxides and sulfides) often possess strong spin-orbit coupling (SOC) because of their high atomic numbers and electron correlation due to their compact d-orbitals. The competition and interplay of SOC and electron interactions is believed to induce a variety of novel electronic and magnetic ground states. In this talk, I will present our recent experimental work on two representative material systems, namely iridates and layered metal sulfides which exhibit a broad spectrum of intriguing physical properties. Continue reading… Shixiong Zhang, Indiana University, Controlled Synthesis and Emergent Properties of Heavy Transition Metal Oxides and Sulfides No Colloquium. Spring Break. Thu. March 14th, 2019 1:00 am-1:00 am Continue reading… No Colloquium. Spring Break. No Colloquium. APS March Meeting. Thu. March 7th, 2019 4:00 pm-5:00 pm Continue reading… No Colloquium. APS March Meeting. Bhupal Dev (Washington University) Tue. March 5th, 2019 11:30 am-12:30 pm New Physics at Neutrino Telescopes Abstract: The recent observation of high-energy neutrinos at the IceCube neutrino telescope has opened a new era in neutrino astrophysics.  Understanding all aspects of these events is very important for both Astrophysics and Particle Physics ramifications.  In this talk, I will discuss a few possible new physics scenarios, such as dark matter, leptoquarks and supersymmetry, that could be probed using the IceCube data.  I will also relate this to the puzzling observation of two upgoing EeV events recently made by the ANITA experiment, which were not seen by IceCube. Continue reading… Bhupal Dev (Washington University) Shulei Zhang, Argonne National Laboratory, From Giant Magnetoresistance to Nonlinear Magnetoresistance in Quantum Materials – An Exciting Journey with Spin Fri. March 1st, 2019 12:45 pm-1:45 pm From Giant Magnetoresistance to Nonlinear Magnetoresistance in Quantum Materials – An Exciting Journey with Spin Shulei Zhang Condensed Matter Theory Group, Materials Science Division, Argonne National Laboratory Abstract: Ever since its surprising emergence from relativistic quantum mechanics, spin has been known as an intrinsic angular momentum that plays a crucial role in electronic structure of matter. When the flows of spin and charge become intertwined through spin-orbit coupling or nontrivial magnetic structures, a host of intriguing magnetotransport phenomena emerge, such as giant magnetoresistance, spin Hall, topological Hall etc. Continue reading… Shulei Zhang, Argonne National Laboratory, From Giant Magnetoresistance to Nonlinear Magnetoresistance in Quantum Materials – An Exciting Journey with Spin Marcelle Soares-Santos (Brandeis University) Thu. February 28th, 2019 4:00 pm-5:00 pm 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. Continue reading… Marcelle Soares-Santos (Brandeis University) Hanna Terletska, Middle Tennessee State University,Understanding quantum materials using computational methods. Wed. February 27th, 2019 12:45 pm-1:45 pm Functional quantum materials, including Mott insulators and high temperature superconductors, are at the forefront of modern materials science and condensed matter physics research. These materials are being actively explored for transformative technological applications, including efficient energy generation, storage and transmission. Understanding the fundamental mechanisms behind the exotic phases of matter emerging in quantum materials is a grand challenge, which must be overcome to maximize technological advancement.             Due to the complexity of the many-electron problem, analytic theories become often unreliable and numerical treatment is required. Over the past decades, numerical analysis has become a very powerful tool for studying strongly correlated electron systems. Continue reading… Hanna Terletska, Middle Tennessee State University,Understanding quantum materials using computational methods. Brian Batell (University of Pittsburgh ) Tue. February 26th, 2019 11:30 am-12:30 pm Breaking Mirror Hypercharge in Twin Higgs Models   The Twin Higgs is a novel framework to understand the stability of the Higgs mass in the face of increasingly stringent LHC bounds on colored top partners. Two principal structural questions in this framework concern the nature of the twin hypercharge gauge symmetry and the origin of the Z2 symmetry breaking needed to achieve the correct vacuum alignment. After an introduction to this framework, a simple extension of the Mirror Twin Higgs model with an exact Z2 symmetry is presented in which a new scalar field in the twin sector spontaneously breaks both twin hypercharge and Z2.   Continue reading… Brian Batell (University of Pittsburgh ) Li Ge, City University of New York, Exploring non-Hermitian symmetries and topology using synthetic photonic materials Mon. February 25th, 2019 12:45 pm-1:45 pm In this talk I will discuss how synthetic photonic materials can be utilized to explore several non-Hermitian symmetries and their topological implications. Although difficult to access in high-energy physics and conventional condensed matter systems, these non-Hermitian symmetries can be realized in photonic materials with carefully arranged gain and loss elements. Therefore, such synthetic photonic materials provide an ideal platform to explore the ramification of these symmetries, including parity-time (PT) symmetry and non-Hermitian particle-hole symmetry, as well as the resulting novel optical phenomena and functionalities. PT symmetric photonics [1] is one of the fastest growing fields in the past five years. Continue reading… Li Ge, City University of New York, Exploring non-Hermitian symmetries and topology using synthetic photonic materials Raman Sundrum (University of Maryland) Thu. February 21st, 2019 4:00 pm-5:00 pm Fundamental Physics and the Fifth Dimension  The central aspirations and successes of Particle Physics will be reviewed against the backdrop of the twin pillars of modern physics,  Relativity and Quantum Mechanics. I will discuss current puzzles such as the Hierarchy Problem, the identity of Dark Matter, and the Matter/Antimatter Asymmetry and how their resolutions may connect to different incarnations of spacetime structure, from curved to higher-dimensional to supersymmetric.  I will describe how these in turn help drive a host of experimental ventures, from the Large Hadron Collider, to dark matter detection experiments, to gravitational wave cosmology.  Continue reading… Raman Sundrum (University of Maryland) Aaron Pierce (University of Michigan-Ann Arbor) Tue. February 19th, 2019 11:30 am-12:30 pm Supersymmetry, Hidden Sectors, and Baryogenesis   Abstract:  Supersymmetry has been a primary target for the experiments at the Large Hadron Collider.  We review what the absence of supersymmetric signals thus far implies for supersymmetric extensions to the Standard Model.  We discuss ways in which supersymmetry might still have important consequences for our Universe — even if it does not completely explain the hierarchy between strength of gravity and the other forces.  As an example, we discuss how a supersymmetric extension might be responsible for generating the observed symmetry between matter and anti-mattter. Continue reading… Aaron Pierce (University of Michigan-Ann Arbor) Ken Singer (CWRU Physics) Thu. February 14th, 2019 4:00 pm-5:00 pm Light-Matter Coupling in Molecular Materials The combination of nanoscale fabrication technology along with the physical analogies between classical electromagnetic waves and quantum mechanical wave functions has opened the door to new classes of optical matter analogs and novel nano-optic metamaterials, such as photonic crystals and hyperbolic metamaterials, among others.  Such structures can be combined with real materials to achieve new forms of matter with a broad range of potential applications.  This presentation describes the incorporation of organic molecular excitonic materials in nanoscale optical cavities.  The resulting cavity polaritons exhibit behavior unique to organic materials and pave the way for room temperature quantum optical structures and effects.  Continue reading… Ken Singer (CWRU Physics) Riccardo Penco (Carnegie Mellon University) Tue. February 12th, 2019 11:30 am-12:30 pm Constraining the gravitational sector with black hole perturbations Geoffrey Landis (NASA Glenn) Thu. February 7th, 2019 4:00 pm-5:00 pm A Physicist on Mars Mars, our nearest neighbor outward in the solar system, is a planet that has fascinated humans for hundreds of years.  Physicist Geoffrey A. Landis of the NASA Glenn Research Center will discuss NASA’s rover missions to Mars, including the mission of the Mars Exploration Rovers, which have been traversing the surface of Mars for a mission of seventeen years, carrying a suite of physics-based instrumentation including hyperspectral cameras, Mössbauer spectrometry, and alpha-induced x-ray fluorescence. This talk will present some results of the many missions that have been (and still are) exploring Mars, Continue reading… Geoffrey Landis (NASA Glenn) Joshua Berger (University of Pittsburgh) Tue. February 5th, 2019 11:30 am-12:30 am Searching for the dark sector in neutrino detectors   Abstract: Dark matter has thus far eluded attempts to determine its non-gravitational interactions, putting strong constraints on a minimal dark sector. I present models of non-minimal dark sectors that could elude current searches, but be seen in current or near future neutrino experiments. I begin by presenting a comprehensive, ongoing phenomenological study of models in which dark matter can annihilate into other forms of dark matter, leading to a flux of energetic (boosted) dark matter (BDM). Such dark matter could deposit enough energy to be detected in large neutrino detectors such as Super-Kamiokande and DUNE. Continue reading… Joshua Berger (University of Pittsburgh) Evelyn Hu (Harvard University) Thu. January 24th, 2019 4:00 pm-4:00 pm “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, Continue reading… Evelyn Hu (Harvard University) James Bonifacio (CWRU) Tue. January 22nd, 2019 11:30 am-12:30 pm Shift Symmetries in (Anti) de Sitter Space 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. Continue reading… Colin McLarty (CWRU Philosophy) Alexis D. Plascencia (CWRU) Tue. January 15th, 2019 11:30 am-12:30 pm Tau-philic dark matter coannihilation at the LHC and CLIC    Abstract: We will discuss a set of simplified models of dark matter with three-point interactions between dark matter, its coannihilation partner and the Standard Model particle, which we take to be the tau lepton. The contribution from dark matter coannihilation is highly relevant for a determination of the correct relic abundance. Although these models are hard to detect using direct and indirect detection, we will show that particle colliders can probe large regions in the parameter space. Some of the models discussed are manifestly gauge invariant and renormalizable, Continue reading… Alexis D. Plascencia (CWRU) Stephane Coutu (Penn State) Tue. December 4th, 2018 11:30 am-12:30 pm Abstract:  Host: Covault Continue reading… Stephane Coutu (Penn State) Samo Kralj,Josef Stefan Institute in Ljubljana and University of Maribor, Slovenia, Topological defects in nematic liquid crystals: playground of fundamental physics Mon. December 3rd, 2018 12:45 pm-1:45 pm Topological defects in nematic liquid crystals: playground of fundamental physics Samo Kralj   1Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia 2Solid State Department, “Jožef Stefan” Institute, Jamova 39, Ljubljana, Slovenia          Topological defects (TDs) are an unavoidable consequence of continuous symmetry breaking phase transitions [1]. They appear at all scales of physical systems, including particle physics, condensed matter and cosmology. Due to their topological origin they display several universalities that are independent of the systems’ microscopic details. Continue reading… Samo Kralj,Josef Stefan Institute in Ljubljana and University of Maribor, Slovenia, Topological defects in nematic liquid crystals: playground of fundamental physics Mark Griswold (CWRU Radiology) Thu. November 29th, 2018 4:00 pm-5:00 pm Continue reading… Mark Griswold (CWRU Radiology) Mark B. Wise (Caltech) Tue. November 27th, 2018 11:30 am-12:30 pm Loop induced inflationary non-Gaussianites that give rise to an  enhanced galaxy power spectrum at small wave-vectors   Abstract:  I outline the calculation of non-Gaussian mass density fluctuations that arise from one-loop Feynman diagrams in a de Sitter background.  Their impact on the distribution of galaxies on very large length scales (i.e. l > 200/ h Mpc) is discussed. The role that  symmetries of the de Sitter metric play in determining the form of the power spectrum,  bi-spectrum and tri-spectrum of primordial curvature perturbations is emphasized. Host: Fileviez Perez Continue reading… Mark B. Wise (Caltech) Jure Zupan (University of Cincinnati) Tue. November 20th, 2018 11:30 am-12:30 pm Effective field theories for dark matter direct detection Abstract: I will discuss the nonperturbative matching of the effective field theory describing dark matter interactions with quarks and gluons to the effective theory of nonrelativistic dark matter interacting with nonrelativistic nucleons. In general, a single partonic operator already matches onto several nonrelativistic operators at leading order in chiral counting. Thus, keeping only one operator at the time in the nonrelativistic effective theory does not properly describe the scattering in direct detection. Moreover, the matching of the axial–axial partonic level operator, as well as the matching of the operators coupling DM to the QCD anomaly term, Continue reading… Jure Zupan (University of Cincinnati) Maryam Ghazisaeidi, Ohio State University, High entropy alloys: mechanical properties and phase stability Mon. November 19th, 2018 12:45 pm-1:45 pm High entropy alloys: mechanical properties and phase stability Maryam Ghazisaeidi, Department of Materials Science and Engineering, Ohio State University The term “High entropy” alloys (HEA) refers to a relatively new class of multicomponent—usually five or more—metallic alloys in equal or near equal atomic concentrations. Instead of ordered intermetallics, expected from classical physical metallurgy, some HEA systems strikingly crystalize as single phase solid solutions with simple crystal structures. The complex compositions of these alloys, and their derivatives, lead to unique properties. They also encourage new ways of viewing fundamentals of physical metallurgy, Continue reading… Maryam Ghazisaeidi, Ohio State University, High entropy alloys: mechanical properties and phase stability 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, Continue reading… Tracy Slatyer (MIT) Jonathan Ouellet (MIT) Tue. November 13th, 2018 11:30 am-12:30 pm First Results from the ABRACADABRA-10cm Prototype The evidence for the existence of Dark Matter is well supported by many cosmological observations. Separately, long standing problems within the Standard Model point to new weakly interacting particles to help explain away unnatural fine-tunings. The axion was originally proposed to explain the Strong-CP problem, but was subsequently shown to be a strong candidate for explaining the Dark Matter abundance of the Universe. ABRACADABRA is a proposed experiment to search for ultralight axion Dark Matter, with a focus on the mass range 10^{-14} ~< Continue reading… Jonathan Ouellet (MIT) Joe Trodahl, Victoria University of Wellington, Rare-earth nitrides; semiconductors, spin/orbit magnetism, tunnelling MRAM, superconductivity Mon. November 12th, 2018 12:45 pm-1:45 pm Rare-earth nitrides; semiconductors, spin/orbit magnetism, tunnelling MRAM, superconductivity Joe Trodahl  MacDiarmid Institute for Advanced Materials and Nanotechnology Victoria University of Wellington New Zealand Controlling the flow of electronic spin in addition to the charge promises speed and power demand advantages. However, there are as yet few “spintronic” devices on the market, in part due to a lack of intrinsic ferromagnetic semiconductors that would permit full exploitation of the coupled spin/charge technology. To date the only full series of such materials are the mononitrides of the lanthanides, the 14 rare-earth elements. Continue reading… Joe Trodahl, Victoria University of Wellington, Rare-earth nitrides; semiconductors, spin/orbit magnetism, tunnelling MRAM, superconductivity 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, Continue reading… Pino Strangi (CWRU Physics) F. De Angelis, Istituto Italiano di Tecnologia, Genoa, Italy, 3D plasmonic nanostructures for biology and medicine Mon. November 5th, 2018 12:45 pm-1:45 pm 3D plasmonic nanostructures for biology and medicine Francesco De Angelis Istituto Italiano di Tecnologia, Genoa, Italy In this talk we will show our last achievements and future perspectives of distinct class of plasmonic devices devoted to biological and medical applications. Among them, we will introduce the concept of meta-electrodes, namely a nanostructured surface that can work as electrode, a broad band plasmonic antenna, and optimal cellular interface (see Figure 1). We show that meta-electrodes combined with commercial CMOS technology enable high quality intracellular electrical signals on the large network scale of human neuron and cardiomyocytes . Continue reading… F. De Angelis, Istituto Italiano di Tecnologia, Genoa, Italy, 3D plasmonic nanostructures for biology and medicine 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].    Continue reading… Federico Capasso (Harvard Univ) Francesc Ferrer (Washington University) Tue. October 30th, 2018 11:30 am-12:30 pm Primordial black holes in the wake of LIGO The detection of gravitational waves from the merger of black holes of ~30 solar masses has reignited the interest of primordial black holes (PBHs) as the source of the dark matter in the universe. We will review the existing constraints on the abundance of PBHs and the implications for several fundamental physics scenarios. A small relic abundance of heavy PBHs may play and important role in the generation of cosmological structures, and we will discuss how such a PBH population can be generated by the collapse of axionic topological defects. Continue reading… Francesc Ferrer (Washington University) Ezekiel Johnston-Halperin, The Ohio State University, Quantum Magnonics in V[TCNE]2 Mon. October 29th, 2018 12:45 pm-1:45 pm Quantum Magnonics in V[TCNE]2   The study of quantum coherent magnonic interactions relies implicitly on the ability to excite and exploit long lived spin wave excitations in a magnetic material. That requirement has led to the nearly universal reliance on yittrium iron garnet (YIG), which for half a century has reigned as the unchallenged leader in high-Q, low loss magnetic resonance, and more recently in the exploration of coherent quantum coupling between magnonic and spin [1] or superconducting [2] degrees of freedom. Surprisingly, the organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]2) has recently emerged as a compelling alternative to YIG. Continue reading… Ezekiel Johnston-Halperin, The Ohio State University, Quantum Magnonics in V[TCNE]2 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, Continue reading… Mike Martens (CWRU Physics) 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. Continue reading… Georgia Karagiorgi (Columbia University) Xiaoju Xu (University of Utah) Tue. October 16th, 2018 11:30 am-12:30 pm Multivariate Dependent Halo and Galaxy Assembly Bias Galaxies form in dark matter halos, and their properties and distributions are connected to the host halos. With a prescription of the galaxy-halo relation and the theoretically known halo clustering (e.g., from N-body simulations), galaxy clustering data from large galaxy surveys can be modeled to learn about galaxy formation and cosmology. In the above halo-based model, it is usually assumed that the statistical distribution of galaxies inside halos only depends on halo mass. However, it is found that in addition to mass halo clustering also depends on the formation history and environment of halos, Continue reading… Xiaoju Xu (University of Utah) Sergey Kravchenko, Northeastern University, The latest developments in the field of the metal-insulator transition in 2D Mon. October 15th, 2018 12:45 pm-1:45 pm Sergey Kravchenko, Northeastern University The latest developments in the field of the metal-insulator transition in 2D Abstract: Ignited by the discovery of the metal-insulator transition, the behavior of low-disorder two-dimensional (2D) electron systems is currently the focus of a great deal of attention. In the strongly-interacting limit, electrons are expected to crystallize into a quantum Wigner crystal (Wigner, 1934), but no definitive evidence for this effect has been obtained despite much experimental effort over the years. Now we have found two-threshold voltage-current characteristics with a dramatic increase in noise between the two threshold voltages. Continue reading… Sergey Kravchenko, Northeastern University, The latest developments in the field of the metal-insulator transition in 2D 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. Continue reading… Brian Keating (UC San Diego) Brad Benson (University of Chicago) Tue. October 9th, 2018 11:30 am-12:30 pm New Results from the South Pole Telescope I will give an overview of the South Pole Telescope (SPT), a 10-meter diameter telescope at the South Pole designed to measure the cosmic microwave background (CMB).  The SPT recently completed 10 years of observations, over which time it has been equipped with three different cameras: SPT-SZ, SPTpol, and SPT-3G. I will discuss recent results from the SPT-SZ and SPTpol surveys, including: an update on the SPT Sunyaev-Zel’dovich (SZ) cluster survey, and joint analyses with the optical dark energy survey (DES); a comparison of CMB measurements between SPT-SZ and the Planck satellite; Continue reading… Brad Benson (University of Chicago) 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. Continue reading… Tim Linden (Ohio State University) Tim Linden (Ohio State University) Tue. October 2nd, 2018 11:30 am-12:30 pm 2018 Michelson Postdoctoral Prize Lecture 2 The Rise of the Leptons: Emission from Pulsars will Dominate the next Decade of TeV Gamma-Ray Astronomy HAWC observations have detected extended TeV emission coincident with the Geminga and Monogem pulsars. In this talk, I will show that these detections have significant implications for our understanding of pulsar emission. First, the spectrum and intensity of these “TeV Halos” indicates that a large fraction of the pulsar spindown energy is efficiently converted into electron-positron pairs. This provides observational evidence necessitating pulsar interpretations of the rising positron fraction observed by PAMELA and AMS-02. Continue reading… Tim Linden (Ohio State University) Tim Linden (Ohio State University) Mon. October 1st, 2018 12:45 pm-1:45 pm Michelson Postdoctoral Prize Lecture 1 Astrophysical Signatures of Dark Matter Accumulation in Neutron Stars Over the past few decades, terrestrial experiments have placed increasingly strong limits on the dark matter-nucleon scattering cross-section. However, a significant portion of the standard dark matter parameter space remains beyond our reach. Due to their extreme density and huge gravitational fields, neutron stars stand as optimal targets to probe dark matter-nucleon interactions. For example, over the last few years, the mere existence of Gyr-age neutron stars has placed strong limits on models of asymmetric dark matter. In this talk, Continue reading… Tim Linden (Ohio State University) 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, what are the prospects for future direct, Continue reading… Dan Hooper (Fermilab) Mahmoud Parvizi (Vanderbilt University) Tue. September 25th, 2018 11:30 am-12:30 pm Cosmological Observables via Non-equilibrium Quantum Dynamics in Non-stationary Spacetimes Abstract:  In nearly all cases cosmological observables associated with quantum matter fields are computed in a general approximation, via the standard irreducible representations found in the operator formalism of particle physics, where intricacies related to a renormalized stress-energy tensor in a non-stationary spacetime are ignored. Models of the early universe also include a hot, dense environment of quantum fields where far-from-equilibrium interactions manifest expressions for observables with leading terms at higher orders in the coupling. A more rigorous treatment of these cosmological observables may be carried out within the alternative framework of algebraic quantum field theory in curved spacetime, Continue reading… Mahmoud Parvizi (Vanderbilt University) Alkan Kabakcioglu, Koc University, DNA folding thermo/dynamics with a twist Mon. September 24th, 2018 12:45 pm-1:45 pm DNA folding thermo/dynamics with a twist Alkan Kabakcioglu, Koc University, Istanbul DNA denaturation is possibly one of the earliest problems in biophysics that grabbed the attention of statistical physicists. The nature of the folding/melting transition has been subject to debate since 60’s until a breakthrough in the past decade mostly settled the question. We recently readdressed the problem for circular DNA (which has a topologically imposed, fixed linking number due to helicity) and found that the melting behavior is qualitatively different from that of the unconstrained DNA with freely dangling ends. Continue reading… Alkan Kabakcioglu, Koc University, DNA folding thermo/dynamics with a twist 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. Continue reading… Charles Rosenblatt (CWRU Physics) Miguel Zumalacarregui (UC Berkeley & IPhT Saclay) Tue. September 18th, 2018 11:30 am-12:30 pm The Dark Universe in the Gravitational Wave Era Evidence shows that we live in a universe where 95% of the matter and energy is of unknown nature. Right from the onset, Gravitational Wave (GW) astronomy is shaping our understanding of the dark universe in several ways: GW signals of black hole mergers have resurrected the idea of Dark Matter being made of primordial black holes, while multi-messenger GW astronomy has generated novel ways to test Dark Energy and the fundamental properties of gravity. I will discuss the impact of gravitational waves on the landscape of gravitational theories, Continue reading… Miguel Zumalacarregui (UC Berkeley & IPhT Saclay) no seminar/faculty meeting Mon. September 17th, 2018 12:45 pm-2:00 pm Continue reading… no seminar/faculty meeting 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. Continue reading… Laura Grego (Union of Concerned Scientists) Andre De Gouvea (Northwestern Univ.) Fri. September 7th, 2018 12:45 pm-1:45 pm Chiral Dark Sectors, Neutrino Masses, and Dark Matter I discuss the hypothesis that there are new chiral fermions particles that transform under a new gauge group. Along the way, I present one mechanism for constructing nontrivial, chiral gauge theory and explore the phenomenology – mostly related to nonzero neutrino masses and the existence of dark matter – associated to a couple of concrete example. Host: Fileviez Perez Continue reading… Andre De Gouvea (Northwestern Univ.) 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. Continue reading… Andre De Gouvea (Northwestern University) Anastasia Fialkov (Harvard Univ.) Tue. August 7th, 2018 11:30 am-12:30 pm SHINING LIGHT INTO COSMIC DARK AGES The first billion years is the least-explored epoch in cosmic history. The first claimed detection of the 21 cm line of neutral hydrogen by EDGES (announced at the end of February this year) – if confirmed – would be the first time ever that we witness star formation at cosmic dawn. Join Dr. Fialkov as she discusses theoretical modeling of the 21 cm signal, summarizes the status of the field after the EDGES detection, and shares thoughts on prospects for future detections of this line. Host: Starkman Continue reading… Anastasia Fialkov (Harvard Univ.) Amy Connolly (The Ohio State University) Tue. May 8th, 2018 11:30 am-12:30 pm High Energy Neutrino Astronomy through Radio Detection  Multimessenger astronomy has entered an exciting new era with the recent discovery of both gravitational waves and cosmic neutrinos.  I will focus on neutrinos as particles that can uniquely probe cosmic distances at the highest energies.  While optical Cerenkov radiation has been used for decades in neutrino experiments, the radio Cerenkov technique has emerged in the last 15 years as the most promising for a long-term program to push the neutrino frontier by over a factor of 1000 in energy.   I will give an overview of the current status and future of the radio neutrino program, Continue reading… Amy Connolly (The Ohio State University) Stuart Raby (Ohio State University) Tue. May 1st, 2018 11:30 am-12:30 am Fitting amu and B physics anomalies with a Z’ and a Vector-like 4th family in the Standard Model The Standard Model is very successful.  Nevertheless, there are some, perhaps significant, discrepancies with data. A particularly interesting set of discrepancies hints at new physics related to muons. I will review the data and recent NP models trying to fit the data.  Then I will discuss a very simple model which is motivated by heterotic string constructions. Continue reading… Stuart Raby (Ohio State University) 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, Continue reading… Laura Gladstone (CWRU Physics) Tyce DeYoung (Michigan State University) Tue. April 24th, 2018 11:30 am-12:30 am First light at the IceCube Neutrino Observatory The IceCube Neutrino Observatory, the world’s largest neutrino detector, monitors a cubic kilometer of glacial ice below the South Pole Station to search for very high energy neutrinos from the astrophysical accelerators of cosmic rays.  Since its commissioning in 2011, IceCube has discovered a flux of TeV-PeV scale astrophysical neutrinos, at a level with significant implications for our understanding of the dynamics of the non-thermal universe.  The sources of this flux have remained elusive, however.  In the last six months, hints to the identity of at least some of the sources may have begun to emerge, Continue reading… Tyce DeYoung (Michigan State University) Wei-Cheng Lee, Binghamton University-SUNY, Orbital Selective Mott Transition in Thin Film VO2 Mon. April 23rd, 2018 12:45 pm-1:45 pm Orbital Selective Mott Transition in Thin Film VO2 Wei-Cheng Lee Department of Physics, Applied Physics, and Astronomy, Binghamton University – SUNY In this talk, evidences of strain-induced modulation of electron correlation effects in the rutile phase of epitaxial VO2/TiO2 will be presented. The strain is engineered by different growth orientations (001), (100), and (110). We find that the hard x-ray photoelectron spectroscopy (HAXPES) reveals significant suppression of the density of states at the Fermi energy in (100) and (110) samples at a temperature well above the metal-insulator transition temperature, but not in the (001) sample. Continue reading… Wei-Cheng Lee, Binghamton University-SUNY, Orbital Selective Mott Transition in Thin Film VO2 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. Continue reading… Jacob Scott (Cleveland Clinic) Camille Avestruz (Kavli Institute for Cosmological Physics, University of Chicago) Tue. April 17th, 2018 11:30 am-1:30 pm Computationally Probing Large Structures We can constrain cosmological parameters by measuring patterns in the large scale structure of our universe, which are governed by the competition between gravitational collapse and the accelerated expansion of our universe.  The most massive collapsed structures are clusters of galaxies, comprised of hundreds to thousands of galaxies.  For galaxy clusters, the telltale cosmological pattern is simply their number count as a function of mass and time.  In this talk, I will discuss the challenges in using galaxy clusters as a probe for cosmology.  We address these challenges through computational methods that explore galaxy formation processes such as energy feedback from active galactic nuclei, Continue reading… Camille Avestruz (Kavli Institute for Cosmological Physics, University of Chicago) Fac. meeting Mon. April 16th, 2018 12:45 pm-1:45 pm Continue reading… Fac. meeting 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. Continue reading… Dimitar Sasselov (Harvard University) 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. Continue reading… Jesse Berezovsky (CWRU Physics) Hayden Lee (Harvard University) Tue. April 3rd, 2018 11:30 am-12:30 am Collider Physics for Inflation Cosmological correlation functions encode the spectrum of particles during inflation, in analogy to scattering amplitudes in colliders. Particles with masses comparable to the Hubble scale lead to distinctive signatures on non-Gaussianities that reflect their masses and spins. In addition, there exists a special class of partially massless particles that have no flat space analog, but could have existed during inflation. I will describe their key spectroscopic features in the soft limits of correlation functions, and discuss scenarios in which they lead to observable non-Gaussianity. Continue reading… Hayden Lee (Harvard University) Susan Fullerton, University of Pittsburgh, Using Ions to Control Transport in 2D Materials Mon. April 2nd, 2018 12:45 pm-1:45 pm Using Ions to Control Transport in 2D Materials Susan Fullerton, University of Pittsburgh   Electrostatic gating of two-dimensional (2D) materials with ions is an effective method to achieve high carrier density (10^13 – 10^14 cm^-2) and excellent gate control by creating an electric double layer (EDL) with large capacitance density (>2 μF/cm^2). I will review our use of EDL gating to investigate transport properties of 2D materials including MoTe2, MoS2 and WSe2, and introduce new device concepts that employ EDL gating as an active device component. These include a monolayer electrolyte for application in flash memory, Continue reading… Susan Fullerton, University of Pittsburgh, Using Ions to Control Transport in 2D Materials Olle Heinonen, Argonne National Laboratories, Quantum Monte Carlo modeling of real materials Fri. March 30th, 2018 3:30 pm-4:30 pm Quantum Monte Carlo modeling of real materials Olle Heinonen, Argonne National Laboratory   Because of recent advances in algorithms and hardware, it is now possible to do quantum Monte Carol simulations of real materials systems, such as correlated oxides, for which standard density functional theory methods have well-known problems. I will here briefly introduce variational and diffusion Monte Carlo methods, and then discuss some results for correlated oxides as well as for some chemical systems. I will end with discussing on-going developments and an outlook towards the future.     Continue reading… Olle Heinonen, Argonne National Laboratories, Quantum Monte Carlo modeling of real materials TBA Thu. March 29th, 2018 4:00 pm-5:00 pm Continue reading… TBA Benjamin Fregoso, Dept of Physics, Kent State University, Nonlinear photocurrents in two-dimensional ferroelectrics and beyond Wed. March 28th, 2018 12:45 pm-1:45 pm Nonlinear photocurrents in two-dimensional ferroelectrics and beyond Benjamin Fregoso, Dept. of Physics, Kent State University Abstract: In recent years, it has become clear the need for efficiently harvesting solar energy. Unfortunately, silicon-based solar cells with high efficiency are very costly. These devices rely on pn-junctions to separate positive and negative charge carries. I this talk, I explore a less known (but very interesting) nonlinear optical effect, so-called shift current’, to generate large photocurrent beyond the pn-junction paradigm. I will describe the shift-current mechanism in insulators and ferroelectrics and its relation to spontaneous electric polarization. Continue reading… Benjamin Fregoso, Dept of Physics, Kent State University, Nonlinear photocurrents in two-dimensional ferroelectrics and beyond Segev BenZvi (University of Rochester) Tue. March 27th, 2018 11:30 am-12:30 am The Latest Results from the HAWC Very High-Energy Gamma-ray Survey The High Altitude Water Cherenkov (HAWC) observatory, located in central Mexico, is conducting a wide-angle survey of TeV gamma rays and cosmic rays from two-thirds of the sky. TeV gamma rays are the highest energy photons ever observed and provide a unique window into the non-thermal universe. These very high energy photons allow HAWC to conduct a broad science program, ranging from studies of particle acceleration in the Milky Way to searches for new physics beyond the Standard Model. In this talk, Continue reading… Segev BenZvi (University of Rochester) 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, Continue reading… Sebastian Deffner (Univ Maryland Baltimore County) Katy Keenan Applied Physics Division, Physical Measurement Lab National Institute of Standards and Technology Quantitative MRI for Precision Medicine Thu. March 22nd, 2018 2:00 pm-3:00 pm IMAGING PHYSICS SEMINAR Katy Keenan Applied Physics Division, Physical Measurement Lab National Institute of Standards and Technology Quantitative MRI for Precision Medicine The ability of MRI to measure real, physical parameters of interest requires reference standards to ensure accuracy and reproducibility of data. Currently, variability exists across MRI systems, manufacturers, models, software versions, and analysis packages, which impedes comparison of data across patients, centers, and time. To move towards precision medicine, we must be able to determine the threshold of normal compared to disease state with a diagnostically useful uncertainty. Continue reading… Katy Keenan Applied Physics Division, Physical Measurement Lab National Institute of Standards and Technology Quantitative MRI for Precision Medicine Cliff Cheung (Caltech) Tue. March 20th, 2018 11:30 am-12:30 pm Unification from Scattering Amplitudes   The modern S-matrix program offers an elegant approach to bootstrapping quantum field theories without the aid of an action.  While most progress has centered on gravity and gauge theory, similar ideas apply to effective field theories (EFTs).  Sans reference to symmetry or symmetry breaking, we show how certain EFTs can be derived directly from the properties of the tree-level S-matrix, carving out a theory space of consistent EFTs from first principles.  Furthermore, we argue that the S-matrix encodes a hidden unification of gravity, gauge theory, and EFTs.  In particular, starting from the tree-level S-matrix of the mother of all theories, Continue reading… Cliff Cheung (Caltech) Debra McGivney, Dept. Radiology CWRU, Inverse Problems in Medical Imaging Tue. March 20th, 2018 1:00 pm-2:00 pm IMAGING PHYSICS SEMINAR Debra McGivney Research Scientist, Department of Radiology Case Western Reserve University Inverse Problems in Medical Imaging Mathematical inverse problems are used to model a wide variety of practical problems, including problems in medical imaging. Here, the unknown of interest is an image of the inside of the human body, which is not directly observable, but must be reconstructed given measurements made outside of the body. Oftentimes, reconstruction problems in imaging are ill-posed, which can result in errors in the reconstructed solution. Medical imaging plays a vital role in the diagnosis, Continue reading… Debra McGivney, Dept. Radiology CWRU, Inverse Problems in Medical Imaging Yuan-Ming Lu, The Ohio State University, Tunable Surface States of Topological Materials Mon. March 19th, 2018 12:45 pm-1:45 pm Tunable Surface States of Topological Materials Yuan-Ming Lu, The Ohio State University   The discovery of topological insulators revealed a large class of topological materials, which exhibit novel surface states with unusual properties. I will discuss some recent progress in engineering surface states of topological materials, focusing on two different systems. The 1st class of materials is three-dimensional Dirac semimetals including Na3Bi and Cd3As2, whose topological surface states can be deformed in these materials by either doping or applying mechanical strain. The 2nd class of materials are spin-orbit coupled quantum magnets, which can host topological magnon surface states robust again disorders. Continue reading… Yuan-Ming Lu, The Ohio State University, Tunable Surface States of Topological Materials Spring Break Thu. March 15th, 2018 4:00 pm-5:00 pm Continue reading… Spring Break Alexey Tonyushkin University of Massachusetts Boston, Breaking the Rules in Magnetic Particle Imaging and Ultra-High Field MRI Thu. March 15th, 2018 12:30 pm-1:30 pm IMAGING PHYSICS SEMINAR Alexey Tonyushkin University of Massachusetts Boston Breaking the Rules in Magnetic Particle Imaging and Ultra-High Field MRI Magnetic Particle Imaging (MPI) is a new tomographic imaging modality that offers high spatial and temporal resolution. Compared to the other imaging modalities such as MRI/CT/PET, MPI is non-toxic, more sensitive, and fully quantitative technique. To date a few small-bore MPI systems were developed, however, human-size MPI scanner has yet to be built. The major challenge of scaling up of MPI is in high power consumption that is associated with the traditional approach to designing the scanner. Continue reading… Alexey Tonyushkin University of Massachusetts Boston, Breaking the Rules in Magnetic Particle Imaging and Ultra-High Field MRI Spring break ( no seminar) Mon. March 12th, 2018 12:45 pm-1:45 pm Continue reading… Spring break ( no seminar) Michael Boss, NIST, Quantitative MRI: from Bench to Bedside Mon. March 12th, 2018 4:30 pm-5:30 pm IMAGING PHYSICS SEMINAR Michael Boss National Institute of Standards and Technology Quantitative MRI: from Bench to Bedside Quantitative MRI: from Bench to Bedside Magnetic Resonance Imaging (MRI) is an exquisite tool for probing the anatomical structure of the human body. It is also capable of measuring physical parameters such as relaxation times, diffusion and temperature, known as quantitative imaging biomarkers (QIBs). When acquired using methods with known limits of bias and reproducibility, these QIBs allow for comparison of scan data across patients, imaging sites, and time, turning into a powerful tool for clinical trials and patient care to evaluate disease state and treatment response. Continue reading… Michael Boss, NIST, Quantitative MRI: from Bench to Bedside APS March Meeting Thu. March 8th, 2018 4:00 pm-5:00 pm Continue reading… APS March Meeting John Beacom (The Ohio State University) Tue. March 6th, 2018 11:30 am-12:30 pm A New Era for Solar Neutrinos Abstract: Studies of solar neutrinos have been tremendously important, revealing the nature of the Sun’s power source and that its neutrino flux is strongly affected by flavor mixing.  Nowadays, one gets the impression that this field is over.  However, this is not due to a lack of interesting questions; it is due to a lack of experimental progress.  I show how this can be solved, opening opportunities for discoveries in particle physics and astrophysics, simultaneously. Continue reading… John Beacom (The Ohio State University) APS March Meeting ( no seminars) Mon. March 5th, 2018 12:45 pm-1:45 pm Continue reading… APS March Meeting ( no seminars) 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. Continue reading… Lindley Winslow (MIT) Lindley Winslow (MIT) Wed. February 28th, 2018 1:30 pm-2:00 pm First Results from CUORE: Majorana Neutrinos and the Search for Neutrinoless Double-Beta Decay The neutrino is unique among the Standard Model particles. It is the only fundamental fermion that could be its own antiparticle, a Majorana particle. A Majorana neutrino would acquire mass in a fundamentally different way than the other particles and this would have profound consequences to particle physics and cosmology. The only feasible experiments to determine the Majorana nature of the neutrino are searches for the rare nuclear process neutrinoless double-beta decay. CUORE uses tellurium dioxide crystals cooled to 10 mK to search for this rare process. Continue reading… Lindley Winslow (MIT) APS March Meeting preview: student practice talks Mon. February 26th, 2018 12:30 pm-2:00 pm Shuhao Liu:  A Temperature Driven Hole-phonon Coupling Enhancement Effect in a Strongly Correlated 2D Hole System. Kasun V. M. N. G. Premasiri:  Tuning Rashba Spin-orbit Coupling in Few-layer InSe. Kyle Crowley: Doping and Field Effect in Novel 2D Layered Oxides Santosh Kumar Radha: Distortion modes in inorganic halide perovskites: to twist or to stretch. Narasak Pandech: First-principles Investigation of The Role of Organic Molecules Inside The α-phase of Hybrid Halide Perovskite CH3NH3BX3 (B= Pb, Continue reading… APS March Meeting preview: student practice talks Andrew Stephens, Northwestern U., Separating the role of chromatin from lamins in mechanics and morphology of the cell nucleus Thu. February 22nd, 2018 4:30 pm-5:30 pm Separating the role of chromatin from lamins in mechanics and morphology of the cell nucleus Andrew Stephens, Northwestern U. The nucleus is the 10 µm ellipse compartment in the cell which must properly transduce or resist biophysical forces to dictate the spatial organization of the 2 meters of genome inside of it. Organization and mechanotransduction determine the expression profile of genome which dictates cell function. Previous studies revealed that the two major contributors to nuclear mechanics are lamins, protein intermediate filaments lining the inner nuclear envelope, and chromatin, the DNA genome and its associated proteins, Continue reading… Andrew Stephens, Northwestern U., Separating the role of chromatin from lamins in mechanics and morphology of the cell nucleus Richard Ruiz (IPPP-Durham, UK) Tue. February 20th, 2018 11:30 am-12:30 am Left-Right Symmetry: At the Edges of Phase Space and Beyond The Left-Right Symmetric model (LRSM) remains one of the best motivated completions of the Standard Model of Particle Physics. Thus far, however, data from the CERN Large Hadron Collider (LHC) tell us that new particles, if they are still accessible, must be very heavy and/or very weakly coupled. Interestingly, these regions of parameter space correspond to collider signatures that are qualitatively and quantitatively different from those developed in pre-LHC times. We present several new LRSM collider signatures for these parameter spaces and show a greatly expanded discovery potential at the 13 TeV LHC and hypothetical future 100 TeV very large hadron collider. Continue reading… Richard Ruiz (IPPP-Durham, UK) Fac. meeting Mon. February 19th, 2018 12:45 pm-1:45 pm No seminar physics fac. meeting Continue reading… Fac. meeting Lydia Kisley, Univ. Illinois at Urbana-Champaign, Proteins in nanoporous hydrogels: adsorption, diffusion, and folding Mon. February 19th, 2018 4:30 pm-5:30 pm Proteins in nanoporous hydrogels: adsorption, diffusion, and folding Lydia Kisley Beckman Institute, University of Illinois at Urbana-Champaign Abstract:  Proteins within nanoporous hydrogels have important biotechnological applications in pharmaceutical purification, tissue engineering, water treatment, biosensors, and medical implants. Yet, oftentimes proteins that are functional in solution lose activity when in contact with soft nanostructured materials due to perturbations in the folded state, conformation, diffusion, and adsorption dynamics of the protein by the material. We have developed several unique nanoscale fluorescent spectroscopies to image the heterogeneity of protein dynamics within hydrogels. Continue reading… Lydia Kisley, Univ. Illinois at Urbana-Champaign, Proteins in nanoporous hydrogels: adsorption, diffusion, and folding 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, Continue reading… Ilya Gruzberg (Ohio State University) Andrew J. Long (Kavli Institute for Cosmological Physics, University of Chicago) Tue. February 13th, 2018 11:30 am-12:30 am Testing baryons from bubbles with colliders and cosmology   “Why is there more matter than antimatter?”  This simple question is arguably the most longstanding and challenging problem in modern cosmology, but with input from the next generation of particle physics experiments we may finally have an answer!  In the talk I will discuss how precision measurements of the Higgs boson at the LHC and future high energy collider experiments will be used to test the idea that the matter-antimatter asymmetry arose during the electroweak phase transition in the fractions of a second after the big bang.  Other cosmological phase transitions can also provide the right environment for generating the matter excess.  Continue reading… Andrew J. Long (Kavli Institute for Cosmological Physics, University of Chicago) 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. Continue reading… The 2017 Nobel Prizes: What were they given for? Ayres Freitas (University of Pittsburgh) Tue. February 6th, 2018 11:30 am-12:30 am Radiative Corrections in Universal Extra Dimensions Universal extra dimensions is an interesting extension of the Standard Model that is naturally protected from electroweak precision constraints and provides a natural dark matter candidate. Its phenomenology at the LHC is strongly affected by radiative corrections. On one hand, QCD corrections are important for understanding the production of heavy gluons and quarks, which are the particles with the largest production rates at the LHC. On the other hand, radiative corrections crucially modify the mass spectrum and interactions of the heavy resonances. This talk will describe recent progress on both of these fronts. Continue reading… Ayres Freitas (University of Pittsburgh) David McKeen (University of Pittsburgh) Tue. January 30th, 2018 11:30 am-12:30 am Neutrino Portal Dark Matter Dark matter that interacts with the standard model (SM) through the “neutrino portal” is a possibility that is relatively less well studied than other scenarios. In such a setup, the dark matter communicates with the SM primarily through its interactions with neutrinos. In this talk, I will motivate neutrino portal dark matter and discuss some new tests of this possibility. Continue reading… David McKeen (University of Pittsburgh) Maxim Dzero, Kent State University, Spins & Knots: The rise of Topology in f-orbital materials Mon. January 29th, 2018 12:45 pm-1:45 pm Spins & Knots: The rise of Topology in f-orbital materials Maxim Dzero Kent State University In my talk I will review the key recent theoretical and experimental works on a new class of topological material systems – topological Kondo insulators, which appear as a result of interplay between strong correlations and spin-orbit interactions. I will discuss the history of Kondo insulators is along with the theoretical models used to describe these heavy fermion compounds. The Fu-Kane method of topological classification of insulators is used to show that hybridization between the conduction electrons and localized f-electrons in these systems gives rise to interaction- induced topological insulating behavior. Continue reading… Maxim Dzero, Kent State University, Spins & Knots: The rise of Topology in f-orbital materials Anders Johan Andreassen (Harvard University) Tue. January 23rd, 2018 11:30 am-12:30 pm Tunneling in Quantum Field Theory and the Ultimate Fate of our Universe One of the most concrete implications of the discovery of the Higgs boson is that, in the absence of physics beyond the standard model, the long-term fate of our universe can now be established through precision calculations. Are we in a metastable minimum of the Higgs potential or the true minimum? If we are in a metastable vacuum, what is its lifetime? To answer these questions, we need to understand tunneling in quantum field theory.This talk will give an overview of the interesting history of tunneling rate calculations and all of its complications in calculating functional determinants of fluctuations around the bounce solutions. Continue reading… Anders Johan Andreassen (Harvard University) Elshad Allahyarov, Duisburg-Essen University and CWRU, Smectic monolayer confined on a sphere: topology at the particle scale Mon. January 22nd, 2018 12:45 pm-1:45 pm Prof. Dr. Elshad Allahyarov,  Duisburg-Essen University, Germany, and  Physics Department  CWRU Smectic monolayer confined on a sphere: topology at the particle scale The impact of topology on the structure of a smectic monolayer confined to a sphere is explored by particle-resolved computer simulations of hard rods. The orientations of the particles are either free or restricted to a prescribed director field with a latitude or longitude orderings. Depending on the imprinted topology, a wealth of different states are found including equatorial smectic with isotropic poles, equatorial smectic with empty poles, Continue reading… Elshad Allahyarov, Duisburg-Essen University and CWRU, Smectic monolayer confined on a sphere: topology at the particle scale 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.   Continue reading… Peter Armitage (Johns Hopkins) Dragan Huterer (U. Michigan) Fri. December 1st, 2017 12:45 pm-1:45 pm title and abstract tba Continue reading… Dragan Huterer (U. Michigan) 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. Continue reading… Dragan Huterer (Univ Michigan) Samo Kralj, University of Maribor, Impact of intrinsic and extrinsic curvature on membrane shapes Wed. November 29th, 2017 12:30 pm-1:30 pm Prof. Samo Kralj University of Maribor, Maribor & Jožef Stefan Institute, Ljubljana, Slovenia    Impact of intrinsic and extrinsic curvature on membrane shapes Red blood cells (erythrocytes) are present in almost all vertebrates and their main function is the transport of oxygen to the body tissues. Their shape dominantly influences their functionality. In almost all mammals in normal conditions erythrocytes adopt a disk-like (discocyte) shape which optimizes their flow properties in large vessels and capillaries. Experimentally measured values  of  the  relative volume v of stable discocyte shapes  range in a relatively broad window. Continue reading… Samo Kralj, University of Maribor, Impact of intrinsic and extrinsic curvature on membrane shapes Arthur Kosowsky (Pittsburgh) Tue. November 28th, 2017 11:30 am-12:30 pm title and abstract tba Continue reading… Arthur Kosowsky (Pittsburgh) No seminar, Faculty meeting Mon. November 27th, 2017 12:45 pm-2:00 pm Continue reading… No seminar, Faculty meeting Farida Selim, Bowling Green State University, Positron Annihilation Spectroscopy and Measurements of Origin of Novel Electronic Phenomena in Semiconductors and Oxides Mon. November 20th, 2017 12:45 pm-1:45 pm Positron Annihilation Spectroscopy and Measurements of Origin of Novel Electronic Phenomena in Semiconductors and Oxides     Farida A. Selim, Department of Physics and Astronomy, Bowling Green State University   Center for Photochemical Sciences, Bowling Green State University  Positron Annihilation Spectroscopy (PAS) has been established as an effective tool to probe electron states and measure atomic scale defects in solids. However, when combined with other techniques, PAS becomes also a powerful tool for revealing and explaining many interesting electronic phenomena. In our laboratory, we combined PAS with structural and transport measurements as well as with infrared, Continue reading… Farida Selim, Bowling Green State University, Positron Annihilation Spectroscopy and Measurements of Origin of Novel Electronic Phenomena in Semiconductors and Oxides 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. Continue reading… A.H. Heuer (CWRU Materials Science and Engineering) Simone Aiola (Princeton) Tue. November 14th, 2017 11:30 am-12:30 pm Cosmology with ACTPol and AdvACT The bolometric polarimeter at the focal plane of the Atacama Cosmology Telescope allows us to map the Cosmic Microwave Background (CMB) with high signal-to-noise both in temperature and polarization.  In this talk, I will present the data-reduction pipeline, highlighting the importance of making maximum-likelihood unbiased CMB maps. I will show the two-season ACTPol cosmological results presented in Louis et al. (2017), Sherwin et al. (2017), and Hilton et al. (2017) and describe the current effort to finalize the analysis of the ACTPol dataset. I will conclude with preliminary results from the ongoing AdvACT survey, Continue reading… Simone Aiola (Princeton) Vincent Sokalski, Carnegie Mellon University, A New Kind of Magnetism – The Dzyaloshinskii-Moriya Interaction Mon. November 13th, 2017 12:45 pm-1:45 pm A New Kind of Magnetism – The Dzyaloshinskii-Moriya Interaction Vincent Sokalski, Dept. of Materials Science and Engineering, Carnegie Mellon University Magnetism has had a profound effect on our everyday lives from compass needles in ancient times to the modern hard disc drive in today’s computers.  The existence of magnetic materials is rooted in the Heisenberg exchange interaction energy, , which favors parallel (or anti-parallel) alignment of neighboring spin vectors and their associated magnetic dipole moments as found, for example, in Fe, Ni, and Co.  In the past decade a different type of magnetic exchange came to the forefront of modern physics called the Dzyaloshinskii-Moriya Interaction (DMI) given by , Continue reading… Vincent Sokalski, Carnegie Mellon University, A New Kind of Magnetism – The Dzyaloshinskii-Moriya Interaction 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, SnS’s intrinsic p-type nature leads to both opportunities and challenges in p-type semiconductor device applications. Continue reading… Xuan Gao (CWRU Physics) Jeanie Lau, The Ohio State University, Spin, Charge and Heat Transport in Low-Dimensional Materials Mon. November 6th, 2017 12:45 pm-1:45 pm Spin, Charge and Heat Transport in Low-Dimensional Materials Chun Ning (Jeanie) Lau Department of Physics, The Ohio State University, Columbus, OH 43210, USA   Low dimensional materials constitute an exciting and unusually tunable platform for investigation of both fundamental phenomena and electronic applications. Here I will present our results on transport measurements of high quality few-layer phosphorene devices, and the unprecedented current carrying capacity of carbon nanotube “hot dogs”. In the second half of the talk, I will present our recent observation of robust long distance spin transport through the antiferromagnetic state in graphene. Continue reading… Jeanie Lau, The Ohio State University, Spin, Charge and Heat Transport in Low-Dimensional Materials James Bonifacio (Oxford and CWRU) Tue. October 31st, 2017 11:30 am-12:30 pm Title: Amplitudes for massive spinning particles  Abstract: I will review a method for constructing scattering amplitudes for spinning particles and then discuss how these amplitudes can be used to constrain massive gravity and theories containing higher-spin particles. Continue reading… James Bonifacio (Oxford and CWRU) 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, Continue reading… Peter Lu (Harvard University) 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, Continue reading… Peter Lu (Harvard University) (Not a Colloquium but of related interest) 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. Continue reading… Jason Alicea (Caltech) Lloyd Knox (UC Davis) Tue. October 17th, 2017 11:30 am-12:30 pm The Standard Cosmological Model: A Status Report Overall, the standard cosmological model has enjoyed enormous empirical success. But there are  a number of indicators that we might be missing something. These include the large-scale cosmic microwave background (CMB) “anomalies”, and two to three sigma discrepancies between cosmological parameters derived from larger angular scales of the CMB vs. smaller angular scales, CMB lensing potential reconstruction vs. CMB power spectra, data from the Planck satellite vs. data from the South Pole Telescope, and CMB-calibrated predictions for  the current rate of expansion vs. more direct measurements. I will introduce the standard cosmological model, Continue reading… Lloyd Knox (UC Davis) Eric Stinaff, Ohio University, Opto-electronic studies of novel self-contacted 2D materials based devices Mon. October 16th, 2017 12:45 pm-1:45 pm Opto-electronic studies of novel self-contacted 2D materials based devices Eric Stinaff Department of Physics and Astronomy, Ohio University Interest in two-dimensional crystals has grown exponentially over the last decade, a testament to their vast technological and scientific potential. In addition to properties such as high mobilities, semiconducting and superconducting behavior, and excellent thermal properties, many of these materials have the potential for novel opto-electronic applications, with large absorption, strong room-temperature emission, non-linear response, and optical control of spin and valley degrees of freedom. In this presentation, we will discuss an experimental investigation of mono-to-few-layer sheets of MoS2 and WS2 employing femtosecond transient absorption spectroscopy (FTAS) and microscopy. Continue reading… Eric Stinaff, Ohio University, Opto-electronic studies of novel self-contacted 2D materials based devices No colloquium this week Thu. October 12th, 2017 4:00 pm-5:00 pm Continue reading… No colloquium this week Rachel Bezanson (Pittsburgh) Tue. October 10th, 2017 11:30 am-12:30 pm Title: The Surprisingly Complex Lives of Massive Galaxies   Abstract: Massive galaxies reside in the densest and most evolved regions of the Universe, yet we are only beginning to understand their formation history. Once thought to be relics of a much earlier epoch, the most massive local galaxies are red and dead ellipticals, with little ongoing star formation or organized rotation. In the last decade, observations of their assumed progenitors have demonstrated that the evolutionary histories of massive galaxies have been far from static. Instead, billions of years ago, massive galaxies were morphologically different: compact, possibly with more disk-like structures, Continue reading… Rachel Bezanson (Pittsburgh) Michael Fisch, Kent State University, X-ray Experiments in Liquid Crystal Science and Technology Mon. October 9th, 2017 12:45 pm-1:45 pm X-ray Experiments in Liquid Crystal Science and Technology Michael Fisch Kent State University   The use of X-rays to study liquid crystals has a long history, and is still of continuing interest.  A brief review of liquid crystals and X-ray diffraction from common liquid crystalline phases will be presented.  Interpretation of the resulting diffraction patterns will be discussed, and some of our current experiments in bent-core molecules and “organic salts will be discussed.  The relationship of these studies to current problems in liquid crystal science and technology will be briefly explored, Continue reading… Michael Fisch, Kent State University, X-ray Experiments in Liquid Crystal Science and Technology 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, Continue reading… Indu Satija (George Mason University) No seminar, faculty meeting Mon. October 2nd, 2017 12:45 pm-2:00 pm Continue reading… No seminar, faculty meeting 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. Continue reading… Idit Zehavi (CWRU, Astronomy) Tiziana Di Matteo (Carnegie Mellon) Tue. September 26th, 2017 11:30 am-12:30 pm The next massive galaxy and quasar frontier at the Cosmic Dawn Many of the advances in our understanding of cosmic structure have come from direct computer modeling. In cosmology, we need to develop computer simulations that cover this vast dynamic range of spatial and time scales. I will discuss recent progress in cosmological hydrodynamic simulations of galaxy formation at unprecedented volumes and resolution. I will focus on predictions for the first quasars and their host galaxies in the BlueTides simulation.  BlueTides is a uniquely large volume and high resolution simulation of the high redshift universe: with 0.7 trillion particles in a volume half a gigaparsec on a side. Continue reading… Tiziana Di Matteo (Carnegie Mellon) Maosheng Miao, California State University Northridge, Automatic search versus chemical rules in materials structure study Mon. September 25th, 2017 12:45 pm-1:45 pm Automatic search versus chemical rules in materials structure study Maosheng Miao Department of Chemistry and Biochemistry, California State University Northridge CA, USA; Beijing Computational Science Research Center, Beijing, China The increase of the computer power in the past decades not only allow us to calculate larger systems with higher accuracy in materials studies, but also provide the opportunity to explore large configuration spaces such as structures and compositions. Automatic structure searches have been very successful in predicting structures of bulk materials. It seems out of question whether the automatic search is advantageous over traditional structure design based on chemical knowledge and intuition. Continue reading… Maosheng Miao, California State University Northridge, Automatic search versus chemical rules in materials structure study 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, Continue reading… Jeremy Levy (Univ Pittsburgh) Laura Gladstone (CWRU) Tue. September 19th, 2017 11:30 am-12:30 pm Neutrinos: cool, cold, coldest   In all of particle physics, neutrinos are some of the most ghostly particles we’ve detected. While the story of their discovery was pretty cool in itself, some modern experiments are even cooler.    The IceCube experiment, located at the geographic South Pole, was originally designed to collect astro-particle data, especially by looking for neutrino point sources as potential sources of the highest energy cosmic rays. But because of its immense fiducial volume, IceCube can collect high-statistic neutrino data, and thus measure oscillation parameters with precision that rivals dedicated oscillation experiments.    The CUORE experiment examines majorana nature of neutrinos by looking for neutrinoless double beta decay in the coldest cubic meter in the Universe, Continue reading… Laura Gladstone (CWRU) 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]. Continue reading… Liang Wu, UC Berkeley, MPPL3, Antiferromagnetic resonance and in-gap terahertz continuum in Kitaev Honeycomb magnet α−RuCl3 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, Continue reading… Liang Wu (Berkeley); Michelson Postdoctoral Prize Lecture Liang Wu, University California Berkeley, MPPL2,Giant nonlinear optical responses in Weyl semimetals Tue. September 12th, 2017 11:30 pm-12:30 pm Giant nonlinear optical responses in Weyl semimetals Recently Weyl quasi-particles have been observed in transition metal monopnictides (TMMPs) such as TaAs, a class of noncentrosymmetric materials that heretofore received only limited attention. The question that arises now is whether these materials will exhibit novel, enhanced, or technologically applicable properties. The TMMPs are polar metals, a rare subset of inversion- breaking crystals that would allow spontaneous polarization, were it not screened by conduction electrons. Despite the absence of spontaneous polarization, polar metals can exhibit other signatures, most notably second-order nonlinear optical polarizability, leading to phenomena such as second-harmonic generation (SHG). Continue reading… Liang Wu, University California Berkeley, MPPL2,Giant nonlinear optical responses in Weyl semimetals Liang Wu, University California Berkeley, MPPL1, Low-energy Electrodynamics of 3D Topological Insulators Mon. September 11th, 2017 12:45 pm-1:45 pm Low-energy Electrodynamics of 3D Topological Insulators   Topological insulators (TIs) are a recently discovered state of matter characterized by an “inverted” band structure driven by strong spin-orbit coupling. One of their most touted properties is the existence of robust “topologically protected” surface states.  I will discuss what topological protection means for transport experiments and how it can be probed using the technique of time- domain THz spectroscopy applied to 3D TI thin films of Bi2Se3.  By measuring the low frequency optical response, we can follow their transport lifetimes as we drive these materials via chemical substitution through a quantum phase transition into a topologically trivial regime [1]. Continue reading… Liang Wu, University California Berkeley, MPPL1, Low-energy Electrodynamics of 3D Topological Insulators 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.  Continue reading… Mike Tamor (Ford Research) Gabriela Marques, National Observatory of Rio de Janeiro and CWRU Tue. September 5th, 2017 11:30 am-12:30 pm title and abstract tba Continue reading… Gabriela Marques, National Observatory of Rio de Janeiro and CWRU 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, Continue reading… Jun Zhu (Penn State) Condensed Matter Seminar: Jie Gao, Missouri University of Science and Technology (University of Missouri – Rolla) Thu. May 11th, 2017 11:30 am-12:30 pm Jie Gao Missouri University of Science and Technology (University of Missouri – Rolla) Tailoring light-matter interaction with metamaterials and metasurfaces Metamaterials and metasurfaces with designed subwavelength nanostructures exhibit intriguing electromagnetic phenomena, such as negative refraction, invisible cloaking, sub-diffraction imaging, near-zero permittivity and hyperbolic dispersion. In this talk, I will present our recent work on tailoring light-matter interaction with metamaterials and metasurfaces, including the realization of enhanced spontaneous emission, ultrasensitive molecule detection, strong plasmon-phonon interaction, optical vortex generation and full-color metasurface hologram. These results present opportunities and challenges in understanding new physics of light-matter interaction in those artificially structured optical materials and realizing many unprecedented applications in nanophotonics. Continue reading… Condensed Matter Seminar: Jie Gao, Missouri University of Science and Technology (University of Missouri – Rolla) Sarah Shandera (Penn State) Tue. May 9th, 2017 11:00 am-12:00 pm Cosmological open quantum systems Our current understanding of the universe relies on an inherently quantum origin for the rich, inhomogeneous structure we see today. Inflation (or any of the alternative proposals for the primordial era) easily generates a universe exponentially larger than what we can observe. In other words, the modes that are observationally accessible make up an open quantum system. I will discuss what we might learn by thinking about the universe in this way, even though the quantum structure is probably not observable. Continue reading… Sarah Shandera (Penn State) 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, Continue reading… Paul Butler (Carnegie Institute of Washington) Ema Dimastrogiovanni (CWRU) Tue. April 25th, 2017 11:00 am-12:00 pm Primordial gravitational waves: Imprints and search Discussed will be some interesting scenarios for the generation of gravitational waves from inflation and the characteristic imprints we can search with upcoming cosmological observations. Continue reading… Ema Dimastrogiovanni (CWRU) CANCELED: Maosheng Miao, California State University Northridge,Simulate to discover: from new chemistry under high pressure to novel two-dimensional materials Mon. April 24th, 2017 12:45 am-1:45 am CANCELED. Will be rescheduled. Simulate to discover: from new chemistry under high pressure to novel two-dimensional materials   Maosheng Miao Department of Chemistry and Biochemistry California State University Northridge, California 91330, USA   The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry, rooted in the atomic shell structure. Within compounds, Group I elements, for example, invariably assume the +1 oxidation state, and their chemical properties differ completely from those of the p-block elements. Continue reading… CANCELED: Maosheng Miao, California State University Northridge,Simulate to discover: from new chemistry under high pressure to novel two-dimensional materials 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, Continue reading… Juan de Pablo (University of Chicago) David Pace, General Atomics, San Diego, The Fast and the Furious: Energetic Ion Transport in Magnetic Fusion Devices Wed. April 19th, 2017 12:45 am-1:45 am The Fast and the Furious: Energetic Ion Transport in Magnetic Fusion Devices D.C. Pace and the DIII-D National Fusion Facility Team General Atomics, P.O. Box 85608, San Diego, CA 92186-5608, USA David Pace Nuclear fusion has the potential to be an energy source that powers society without generating greenhouse gases or high-level radioactive waste. The tokamak approach to controlled nuclear fusion employs a toroidally-shaped magnetic field configuration to confine plasmas at temperatures beyond 200 million K (20 keV). Future reactors aim to utilize the deuterium-tritium fusion reaction due to its favorable cross-section, Continue reading… David Pace, General Atomics, San Diego, The Fast and the Furious: Energetic Ion Transport in Magnetic Fusion Devices Matthew Johnson (Perimeter Institute) Tue. April 18th, 2017 11:00 am-12:00 pm Mapping Ultra Large Scale Structure Anomalies in the CMB on large angular scales could find an explanation in terms of pre-inflationary physics or intrinsic statistical anisotropies. However, due to cosmic variance it is difficult to conclusively test many of these ideas using the primary cosmic microwave background (CMB) alone. In this talk, I will outline a program to place stringent observational constraints on theories that predict ultra-large scale structure or statistical anisotropies using the secondary CMB (the Sunyaev Zel’dovich effect, polarization form the post-reionization era, lensing, etc.) and tracers of large-scale structure. These methods will become accessible with next-generation CMB experiments and planned galaxy surveys. Continue reading… Matthew Johnson (Perimeter Institute) Louis F. Piper, Binghamton University, Shining new light on old problems in lithium ion batteries Mon. April 17th, 2017 12:45 am-1:45 am Shining new light on old problems in lithium ion batteries   Louis Piper Binghamton University, State University of New York   Improving the energy storage and release of lithium ion battery is largely limited to the cathode (positive electrode).  Commercial high capacity LIBs employ Ni-rich layered oxides (derived from LiCoO2) as cathodes.  In these systems, the reversible energy storage capacity is limited to 1 Li+ per transition metal (i.e. Co3+/4+ redox couple).  However, only 2/3 of Li+ per redox couple are typically intercalated due to capacity retention issues with fast cycling and high voltages.  Continue reading… Louis F. Piper, Binghamton University, Shining new light on old problems in lithium ion batteries 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. Continue reading… Lutz Schimansky-Geier (Humboldt University at Berlin) David Chuss (Villanova) Tue. April 11th, 2017 11:00 am-12:00 pm The Cosmology Large Angular Scale Surveyor (CLASS) Precise observations of the cosmic microwave background have played a leading role in the development of the LCDM model of cosmology, which has been successful in describing the universe’s energy content and evolution using a mere six parameters. With this progress have come hints that the universe underwent an inflationary epoch during its infancy.  Cosmic inflation is predicted to produce a background of gravitational waves that would imprint a distinct polarized pattern on the cosmic microwave background (CMB). Measurement of this polarized signal would provide the first direct evidence for inflation and would provide a means to study physics at energy scales around the predicted GUT scale.  Continue reading… David Chuss (Villanova) Nandini Trivedi, The Ohio State University, Novel magnetic phases in spin-orbit coupled oxides Mon. April 10th, 2017 12:45 pm-1:45 pm Novel magnetic phases in spin-orbit coupled oxides Nandini Trivedi,   Department of Physics, The Ohio State University   Abstract: I will discuss puzzles about magnetism in some of the simplest oxide materials with a single electron in the d-orbital.  Starting from a microscopic model of a Mott insulator with both spins and orbitals, I will obtain the effective magnetic Hamiltonian and provide insights into the experimental puzzles.  Continue reading… Nandini Trivedi, The Ohio State University, Novel magnetic phases in spin-orbit coupled oxides 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, Continue reading… Cristina Marchetti (Syracuse) Donghui Jeong (Penn State) Tue. April 4th, 2017 11:00 am-12:00 pm Non-linearities in large-scale structure: Induced gravitational waves, non-linear galaxy bias I will present my recent work on non-linearities in large-scale structures of the Universe. For the first part, I will discuss the gauge dependence of the scalar-induced tensor perturbations and its implication on searching the primordial gravitational wave signature from the large-scale structure. For the second part of the talk, I will give a brief overview of the recent review on large-scale galaxy bias (Desjacques, Jeong & Schmidt, 1611.09787) that contains a complete expression for the perturbative bias expansion that must hold on large scales. Continue reading… Donghui Jeong (Penn State) Nate Stern, Northwestern University, Monolayer Semiconductor Opto-Electronics: Controlling Light and Matter in Two-Dimensional Materials Mon. April 3rd, 2017 12:45 pm-1:45 pm Monolayer Semiconductor Opto-Electronics: Controlling Light and Matter in Two-Dimensional Materials Nathaniel Stern Department of Physics and Astronomy, Northwestern University The discovery of monolayer two-dimensional semiconductors of atomic-scale thickness presents a new two-dimensional landscape in which to play with the interaction between light and matter. These nanomaterials at the extreme limit of surface-to-volume ratio exhibit rich optical phenomenology such as layer dependent bandgaps and degenerate, but distinct, valley-polarized excitonic states. The unique features of atomically-thin materials suggest that these layered systems can be exploited to achieve new regimes of light-matter interactions. Continue reading… Nate Stern, Northwestern University, Monolayer Semiconductor Opto-Electronics: Controlling Light and Matter in Two-Dimensional Materials 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, Continue reading… Michael Weiss (CWRU Biochemistry) Ben Monreal (CWRU) Tue. March 28th, 2017 11:00 am-12:00 pm Nuclei, neutrinos, and microwaves: searching for the neutrino mass in tritium decay When Enrico Fermi published his theory of beta decay in 1934—what we now call the weak interaction—he suggested how experiments could measure the neutrino mass: by looking at the shape of the energy distribution of beta decay electrons.  We’re still doing exactly that!  I will talk about the state of the art of tritium beta decay electron measurements: the KATRIN experiment, which starts science runs soon with a molecular tritium source towards sub-0.3 eV sensitivity; and the Project 8 experiment, which aims to develop a future atomic tritium experiment sensitive to neutrino masses below 0.05 eV.   Continue reading… Ben Monreal (CWRU) 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.   Continue reading… Mark Wise (Caltech) Note non-standard time Paul Kelly, University of Twente, Turning up the heat in first principles Quantum Spin Transport Wed. March 22nd, 2017 12:45 pm-1:45 pm Turning up the heat in first principles Quantum SpinTransport  Paul J. Kelly Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands   The spin Hall angle (SHA) is a measure of the efficiency with which a transverse spin current is generated from a charge current by the spin-orbit coupling and disorder in the spin Hall effect (SHE). In a study of the SHE for a Pt|Py (Py=Ni80Fe20) bilayer using a first-principles scattering approach, we find a SHA that increases monotonically with temperature and is proportional to the resistivity for bulk Pt. Continue reading… Paul Kelly, University of Twente, Turning up the heat in first principles Quantum Spin Transport Mauricio Bustamante (CCAPP, OSU) Tue. March 21st, 2017 11:00 am-12:00 pm Prospecting for new physics with high-energy astrophysical neutrinos High-energy astrophysical neutrinos, recently discovered by IceCube, are fertile ground to look for new physics.  Due to the high neutrino energies — tens of TeV to a few PeV — we can look for new physics at unexplored energies.  Due to their cosmological-scale baselines — Mpc to Gpc — tiny new-physics effects, otherwise unobservable, could accumulate and become detectable.  Possibilities include neutrino decay, violation of fundamental symmetries, and novel neutrino-neutrino interactions.  I will show that the spectral features, angular distribution, and flavor composition of neutrinos could reveal the presence of new physics and, Continue reading… Mauricio Bustamante (CCAPP, OSU) No Seminar, APS March Meeting and Spring Break Mon. March 13th, 2017 1:00 am-1:00 am Continue reading… No Seminar, APS March Meeting and Spring Break 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. Continue reading… Herbert Levine (Rice Bioengineering) Robert Caldwell (Dartmouth) Tue. March 7th, 2017 11:00 am-12:00 pm Cosmology with Flavor-Space Locked Fields We present new models of cosmic acceleration built from a cosmological SU(2) field in a flavor-space locked configuration. We show that such fields are gravitationally birefringent, and absorb and re-emit gravitational waves through the phenomenon of gravitational wave — gauge field oscillations. As a result, a cosmological SU(2) field leaves a unique imprint on both long-wavelength gravitational waves of primordial origin as well as high frequency waves produced by astrophysical sources. We show that these effects may be detected in the future using the cosmic microwave background and gravitational wave observatories. Continue reading… Robert Caldwell (Dartmouth) 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. Continue reading… Glenn Starkman (Physics) Francesca F. Serra, Johns Hopkins University, Control of liquid crystals through topography for optics and assembly Mon. February 27th, 2017 12:45 pm-1:45 pm Control of liquid crystals through topography for optics and assembly  Dr. Francesca Serra  Physics and Astronomy  Johns Hopkins University   Soft materials are a promising tool to explore controllable energy landscapes. Liquid crystals, in particular, combine reconfigurability, unique optical properties and the possibility of directing their self-assembly via the bounding surfaces. I will show, for example, how smectic-A liquid crystals under different boundary conditions create microlens arrays made of focal conic defects or light guides in an aqueous solution. Focal conic domains act as gradient refractive index lenses that can be assembled and ordered exploiting topographical cues. Continue reading… Francesca F. Serra, Johns Hopkins University, Control of liquid crystals through topography for optics and assembly 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.  Continue reading… Corbin Covault (CWRU) Hamza Balci, Kent State University, A Single Molecule Approach to Study Protein, Small Molecule, and G-Quadruplex Mon. February 20th, 2017 12:45 pm-1:45 pm A Single Molecule Approach to Study Protein, Small Molecule, and  G-Quadruplex Interactions Hamza Balci Kent State University, Physics Department, Kent, OH   G-quadruplex (GQ) structures are non-canonical nucleic acid secondary structures that form in guanine-rich segments of the genome, most prominently at telomeres. In addition, several hundred thousand potential GQ forming sequences have been identified in human genome, with particularly higher frequency at promoter regions. When GQ structures (GQs) form at telomeres, they cap chromosome ends and are involved in stabilizing these vulnerable regions. Also, GQs have been shown to regulate transcription and translation level gene expression when they form in promoter regions of DNA and 5′-UTR of RNA, Continue reading… Hamza Balci, Kent State University, A Single Molecule Approach to Study Protein, Small Molecule, and G-Quadruplex – Thu. February 16th, 2017 4:00 pm-5:00 pm Continue reading… – Matthew Baumgart (Perimeter Institute) Tue. February 14th, 2017 11:00 am-12:00 pm De Sitter Wavefunctionals and the Resummation of Time The holographic RG of Anti-De Sitter gives a powerful clue about the underlying AdS/CFT correspondence. The question is whether similar hints can be found for the heretofore elusive holographic dual of De Sitter. The framework of stochastic inflation uses nonperturbative insight to tame bad behavior in the perturbation series of a massless scalar in DS at late times. Remarkably, this fully quantum system loses phase information and exhibits semiclassical dynamics in the leading approximation. Recasting this as a “resummation of time,” we wish understand whether the distributions that result can be thought of as an attractive UV fixed point of a theory living on a spacelike slice of DS. Continue reading… Matthew Baumgart (Perimeter Institute) 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; Continue reading… The 2016 Science Nobel Prizes – What were they given for? Andrew Zentner (Pittsburgh) Tue. February 7th, 2017 11:00 am-12:00 pm The Power-Law Galaxy Correlation Function For nearly 40 years, the galaxy-galaxy correlation function has been used to characterize the distribution of galaxies on the sky. In addition, the galaxy correlation function has been recognized as very nearly power-law like despite the fact that it is measured over a wide range of scales. In particular, the galaxy correlation function has been measured on very large scales (~30 Mpc), on which density fluctuations are mild and perturbative approaches are appropriate, as well as very small scales (~0.1 Mpc), on which the evolution of the density field of the universe is quite nonlinear. Continue reading… Andrew Zentner (Pittsburgh) Saw-Wai Hla, Ohio University, Operating Individual Quantum Molecular Machines Mon. February 6th, 2017 12:45 pm-1:45 pm Operating Individual Quantum Molecular Machines Saw-Wai Hla  Department of Physics & Astronomy, Ohio University, OH 45701, USA and Nanoscience and Technology Division, Argonne National Laboratory, IL 60439, USA. E-mail: hla@ohio.edu , URL: www.phy.ohiou.edu/~hla   A recent emergent research direction is the development of complex molecular machines suitable to operate on solid surfaces. Biological machines have the sizes from tens of nanometers to a few microns –a range where classical machine concepts hold while artificially designed molecular machines can be in the size range of a few nanometers or less, Continue reading… Saw-Wai Hla, Ohio University, Operating Individual Quantum Molecular Machines – Thu. February 2nd, 2017 4:00 pm-5:00 pm Continue reading… – Kurt Hinterbichler (CWRU) Tue. January 31st, 2017 11:00 am-12:00 pm Partially Massless Higher-Spin Gauge Theory The higher spin theories of Vasiliev are gauge theories that contain towers of massless particles of all spins, and are thought to be UV complete quantum theories that include gravity, describing physics at energies much higher than the Planck scale. We discuss Vasiliev-like theories that include towers of massless and partially massless fields. These massive towers can be thought of as partially Higgs-ed versions of Vasiliev theory. The theory is a fully non-linear theory which contains partially massless modes, is expected to be UV complete, includes gravity, and can live on dS as well as AdS. Continue reading… Kurt Hinterbichler (CWRU) Mike Boss, NIST, Physics and Impact of Quantitative Magnetic Resonance Imaging Mon. January 30th, 2017 12:45 pm-1:45 pm Physics and Impact of Quantitative Magnetic Resonance Imaging Michael Boss, Applied Physics Division National Institute of Standards and Technology, Boulder, CO Each year, millions of U.S. patients are scanned using Magnetic Resonance Imaging (MRI), costing billions of dollars.  The resultant images are typically qualitative, limiting the ability to compare results across patients, time, and scanners. However, a suite of physical parameters (e.g., relaxation times, diffusion coefficients) are interrogable with magnetic resonance, enabling quantitative imaging biomarkers (QIBs). QIBs can provide threshold values for disease diagnosis, allow meaningful measurement of longitudinal change for evaluating treatment response, Continue reading… Mike Boss, NIST, Physics and Impact of Quantitative Magnetic Resonance Imaging Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer Fri. January 27th, 2017 12:45 pm-1:45 pm Quantum Loop States in Spin-Orbital Models on the Honeycomb and Hyperhoneycomb Lattices In the quest for quantum spin liquids, the challenges are many: neither is it clear how to look for nor how to describe them, and definitive experimental examples of quantum spin liquids are still missing. In this talk I will show how to devise a realistic model on the honeycomb lattice whose ground state realizes Haldane chains whose physical supports fluctuate, hence naturally providing the hallmark “fractional excitations” of quantum spin liquids. When taken to the three-dimensional hyperhoneycomb lattice, the ground state becomes a full-fledged symmetry-enriched U(1) quantum spin-orbital liquid, Continue reading… Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer 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, Continue reading… Lucile Savary (MIT) – Michelson Postdoctoral Prize Lecture Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer Tue. January 24th, 2017 11:00 am-12:00 pm Quantum Spin Ice Recent work has highlighted remarkable effects of classical thermal fluctuations in the dipolar spin ice compounds, such as “artificial magnetostatics.” In this talk, I will address the effects of terms which induce quantum dynamics in a range of models close to the classical spin ice point. Specifically, I will focus on Coulombic quantum spin liquid states, in which a highly entangled massive superposition of spin ice states is formed, allowing for dramatic quantum effects: emergent quantum electrodynamics and its associated emergent electric and magnetic monopoles. I will also discuss how random disorder alone may give rise to both a quantum spin liquid and a Griffiths Coulombic liquid–a Bose glass-like phase. Continue reading… Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer Michael Snure, AFRL, Two dimensional BN an atomically thin insulator, substrate, and encapsulation layer from growth to application Mon. January 23rd, 2017 12:45 pm-1:45 pm Two dimensional BN an atomically thin insulator, substrate, and encapsulation layer from growth to application Michael Snure Air Force Research Laboratory, Sensors Directorate, Wright Patterson AFB, OH Since free standing graphene was found in 2004, there has been an explosion of research on atomically thin two dimensional (2D) materials based isolated sheets of layered van der Waals solids.  The spectacular electrical and thermal transport properties of graphene generated a great deal of hype making it a heavily researched material for ultra-high-speed electronics; however, strong interaction with conventional 3D substrates and the lack of a band gap has proven to degrade properties and limit its usefulness in these devices.  Continue reading… Michael Snure, AFRL, Two dimensional BN an atomically thin insulator, substrate, and encapsulation layer from growth to application Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer Mon. January 23rd, 2017 4:15 pm-5:15 pm A New Type of Quantum Criticality in the Pyrochlore Iridates The search for truly quantum phases of matter is one of the center pieces of modern research in condensed matter physics. Quantum spin liquids are exemplars of such phases. They may be considered “quantum disordered” ground states of spin systems, in which zero point fluctuations are so strong that they prevent conventional magnetic long range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects, Continue reading… Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer 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?  Continue reading… Kathy Kash (CWRU Physics) Claire Zukowski (Columbia U.) Tue. January 17th, 2017 11:00 am-12:00 pm Emergent de Sitter Spaces from Entanglement Entropy A theory of gravity can be holographically “emergent” from a field theory in one lower dimension. In most known cases, the gravitational theory lives in an asymptotically anti- de Sitter spacetime with very different properties from our own de Sitter universe. I will introduce a second emergent “auxiliary” spacetime constructed from the entanglement entropy of subregions in the field theory. In 2d, this auxiliary space is either a de Sitter spacetime or its various identifications. The modular Hamiltonian, which encodes information about the entanglement properties of a state in the field theory, Continue reading… Claire Zukowski (Columbia U.) 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. Continue reading… Pavel Fileviez Perez (CWRU Physics) Beatrice Bonga (Penn State) Tue. December 6th, 2016 11:00 am-12:00 pm The closed universe and the CMB Cosmic microwave background (CMB) observations put strong constraints on the spatial curvature via estimation of the parameter $\Omega_k$. This is done assuming a nearly scale-invariant primordial power spectrum. However, we found that the inflationary dynamics is modified due to the presence of spatial curvature leading to corrections to the primordial power spectrum. When evolved to the surface of last scattering, the resulting temperature anisotropy spectrum shows deficit of power at low multipoles ($\ell<20$). This may partially explain the observed $3 \sigma$ anomaly of power suppression for $\ell <30$. Since the curvature effects are limited to low multipoles, Continue reading… Beatrice Bonga (Penn State) Christopher Wolverton, Northwestern University, Accelerating Materials Discovery with Data-Driven Atomistic Computational Tools Mon. December 5th, 2016 12:45 pm-1:45 pm Accelerating Materials Discovery with Data-Driven Atomistic Computational Tools Chris Wolverton Dept. of Materials Science and Eng., Northwestern University, Evanston, IL (USA) c-wolverton@northwestern.edu   Many of the key technological problems associated with alternative energies (e.g., thermoelectrics, advanced batteries, hydrogen storage, etc.) may be traced back to the lack of suitable materials. Both the materials discovery and materials development processes may be greatly aided by the use of computational methods, particular those atomistic methods based on density functional theory (DFT).   Here, we present an overview of our recent work utilizing high-throughput computation and data mining approaches to accelerate materials discovery, Continue reading… Christopher Wolverton, Northwestern University, Accelerating Materials Discovery with Data-Driven Atomistic Computational Tools Mike Hinczewski (CWRU Physics) Thu. December 1st, 2016 4:00 pm-5:00 pm Continue reading… Mike Hinczewski (CWRU Physics) Yi-Zen Chu (University of Minnesota, Duluth) Tue. November 29th, 2016 11:00 am-12:00 pm Causal Structure Of Gravitational Waves In Cosmology Despite being associated with particles of zero rest mass, electromagnetic and gravitational waves do not travel solely on the null cone in generic curved spacetimes. (That is, light does not always propagate on the light cone.) This inside-the-null-cone propagation of waves is known as the tail effect, and may have consequences for the quantitative prediction of gravitational waves from both in-spiraling binary compact stars/black holes and “Extreme-Mass-Ratio” systems. The latter consists of compact objects orbiting, and subsequently plunging into, the horizons of super-massive black holes astronomers now believe reside at the center of many (if not all) galaxies — Continue reading… Yi-Zen Chu (University of Minnesota, Duluth) Marie-Charlotte Renoult, Université de Rouen, Free falling jets of a viscoelastic solution Wed. November 23rd, 2016 12:45 pm-1:45 pm Title: Free falling jets of a viscoelastic solution Prof. Marie-Charlotte Renoult Université de Rouen, France Abstract: We conducted free falling jet experiments of a Newtonian solution with a polymer additive, i.e., a viscoelastic solution.Viscoelastic jets usually break up with the formation of beads-on-a-string (BOAS) structures, where large beads are connected by thin threads. These structures form when the polymer solution begins to exhibit strain-hardening, i.e., an increase in extensional viscosity with extensional rate. Associated with this viscoelastic property is a characteristic relaxation time.In this presentation, two methods of image analysis will be presented: a shape analysis and a multi-scale analysis that are applied to a large number of free falling jet visualisations performed at different jet velocities.The results obtained demonstrate the power of these two experimental techniques to gain a deeper insight into BOAS formation and to probe complex liquid rheology such as the subtle measurement of the polymer relaxation time. Continue reading… Marie-Charlotte Renoult, Université de Rouen, Free falling jets of a viscoelastic solution Daniel Winklehner (MIT) Tue. November 22nd, 2016 11:00 am-12:00 pm On the development and applications of high-intensity cyclotrons in neutrino physics and energy research The cyclotron is one of, if not the, most versatile particle accelerator ever conceived. Based on the (then revolutionary) principle of cyclic acceleration using RF frequency alternating voltage on a so-called dee, while particles are forced into circular orbits by a strong vertical magnetic field, many varieties have been developed in the 84 years since their invention by Lawrence in 1932. The fact that they are still around and oftentimes in a form that has been proposed many years ago is a testimony to their robustness and versatility. Continue reading… Daniel Winklehner (MIT) Keji Lai, Univ of Texas, Austin/Microwave Imaging of Edge States and Electrical Inhomogeneity in 2D Materials Mon. November 21st, 2016 12:45 pm-1:45 pm The understanding of various types of disorders in 2D materials, including dangling bonds at the edges, defects in the bulk, and charges in the substrate, is of fundamental importance for their applications in electronics and photonics. Because of the imperfections, electrons moving on the 2D plane experience a spatially non-uniform Coulomb environment, whose effect on the charge transport has not been microscopically probed. Using a non-invasive microwave impedance microscope with ~100nm resolution and ~1nS sensitivity, we can visualize the spatial evolution of the insulator-to-metal transition in mono-layer and few-layer MoS2 field-effect transistors. As the transistors are gradually turned on, electrical conduction emerges initially at the edges before appearing in the bulk, Continue reading… Keji Lai, Univ of Texas, Austin/Microwave Imaging of Edge States and Electrical Inhomogeneity in 2D Materials 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, Continue reading… Robert Owen (Oberlin College) Austin Joyce (Kavli Institute for Cosmological Physics, Chicago) Tue. November 15th, 2016 11:00 am-12:00 pm Soft limits, asymptotic symmetries, and inflation in Flatland There has been much recent interest in soft limits, both of flat space S-Matrix elements and of cosmological correlation functions. I will discuss the physics probed by soft limits in cosmology and explore the connection between cosmological soft theorems and asymptotic symmetries. These ideas will be illustrated by a simple example: inflation in 2+1 dimensions. Continue reading… Austin Joyce (Kavli Institute for Cosmological Physics, Chicago) Salah Eddine Boulfelfel, Georgia Institute of Technology, Atomic-Scale Modeling of Activated Processes in the Solid State Mon. November 14th, 2016 12:45 pm-1:45 pm Atomic-Scale Modeling of Activated Processes in The Solid State Salah Eddine Boulfelfel School of Chemical and Biomolecular Engineering Georgia Institute of Technology In the practice of solid-state chemistry, processes either thermally-activated or induced by external high-pressure are common events. Often, the simplicity of the material’s structure involved in the activated process is in contrasts with the theoretical and experimental difficulties in assessing its mechanism. Large hysteresis effects, nucleation and growth scenarios, and first-order kinetics require dedicated computational approaches in order to correctly unravel the complex nature of activated process at the atomistic level of details. Continue reading… Salah Eddine Boulfelfel, Georgia Institute of Technology, Atomic-Scale Modeling of Activated Processes in the Solid State 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. Continue reading… Marija Drndic (University of Pennsylvania) Rachel Rosen (Columbia University) Tue. November 8th, 2016 11:00 am-12:00 pm Non-Singular Black Holes in Massive Gravity When starting with a static, spherically-symmetric ansatz, there are currently two types of black hole solutions in massive gravity: (i) exact Schwarzschild solutions which exhibit no Yukawa suppression at large distances and (ii) solutions which contain coordinate-invariant singularities at the horizon.  In this talk, I will present new black hole solutions which have a nonsingular horizon and can potentially be matched to Yukawa asymptotics at large distances.  These solutions recover Schwarzschild black holes in the massless limit and are thus observationally viable.” Continue reading… Rachel Rosen (Columbia University) Jim Andrews, Youngstown State University, Coherent Perfect Polarization Rotation–Beyond the Anti-Laser Mon. November 7th, 2016 12:45 pm-1:45 pm We describe the distinguishing characteristics of coherent perfect optical conversion processes using two-beam interference, as compared to single-beam ‘critical coupling’ processes.  We extend the application of two-port coherent conversion processes to magneto-optical (Faraday) rotation in structured systems and present our recent laboratory demonstration of coherent perfect polarization rotation (CPR) which is a conservative, reversible counterpart to coherent perfect absorption (CPA, or the so-called ‘anti­laser’). conclude with a brief summary of theoretical studies suggesting a CPR-based miniaturization of optical isolators and the extension of coherent perfect  phenomena in non-linear optics. Continue reading… Jim Andrews, Youngstown State University, Coherent Perfect Polarization Rotation–Beyond the Anti-Laser Tao Han (University of Pittsburgh) Fri. November 4th, 2016 11:00 am-12:00 pm Splitting and showering in the electroweak sector We derive the splitting functions for the Standard Model electroweak sector at high energies, including the fermions, massive gauge bosons and the Higgs boson. We study the class of functions with the “ultra-collinear” behavior that is a consequence of the electroweak symmetry breaking. We stress the leading-order corrections to the “Goldstone-boson Equivalence Theorem”. We propose a novel gauge, dubbed the “Goldstone Equivalence Gauge” that practically as well as conceptually disentangles the effects from the Goldstone bosons and the gauge fields. We also demonstrate a practical scheme for multiple electroweak boson production via showering at high energies. Continue reading… Tao Han (University of Pittsburgh) 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, Continue reading… Tao Han (University of Pittsburgh) Samo Kralj, University of Maribor, Effective Topological Charge Cancellation Mechanism Mon. October 31st, 2016 1:00 pm-2:00 pm Effective Topological Charge Cancellation Mechanism Samo Kralj1,2 1FNM, University of Maribor, Koroška 160, 2000 Maribor, Slovenia 2Jožef Stefan Institute, Jamova 39,1000 Ljubljana, Slovenia Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions [1]. Topological origin makes their key features independent of systems’ microscopic details and therefore TDs display many universalities. In general, TDs have strong impact on material properties and play signiﬁcant role in several technological applications. Furthermore, investigations of TDs in relevant fields are interesting for fundamental science. Continue reading… Samo Kralj, University of Maribor, Effective Topological Charge Cancellation Mechanism 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, Continue reading… Andrew Rappe (University of Pennsylvania) Patrick Woodward, The Ohio State University, The magnetism of double perovskites containing osmium and rhenium Mon. October 24th, 2016 12:45 pm-1:45 pm Patrick M. Woodward Department of Chemistry and Biochemistry, The Ohio State University Over the past several years we have been synthesizing and studying the magnetic properties of A2MOsO6 and A2MReO6 (Mg, Zn, Cr, Fe, Co, Ni) double perovskites in a quest to understand how the sign and strength of the superexchange interactions change as a function of the relative filling of the 3d and 5d orbitals, as well as the geometry of the crystal structure. In double perovskites where the 5d ion is the only magnetic ion we find that spin-orbit coupling plays a role, Continue reading… Patrick Woodward, The Ohio State University, The magnetism of double perovskites containing osmium and rhenium 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. Continue reading… Jim Van Orman (CWRU EEES) Sean Bryan (Arizona State University) Tue. October 18th, 2016 11:00 am-12:00 pm Cosmology with Millimeter Wave LEKIDs: CMB, Spectroscopy, and Imaging with TolTEC Millimeter-wave cameras offer a unique window on the history and dynamics of the universe. Observations of CMB polarization are setting new constraints on cosmic inflation and gravitational lensing. Imaging and spectroscopy in millimeter waves measures individual galaxies through their bolometric flux as well as C+/CO line strengths. In this talk, I will discuss aluminum LEKID detectors that can be used for all of these applications. The feed structures are directly machined in metal, and the detectors are made with a single-layer process. Lab measurements show that the 150 GHz dual-polarization detectors have photon-noise limited sensitivity, Continue reading… Sean Bryan (Arizona State University) 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, Continue reading… Mark Newman (University of Michigan) Stacy McGaugh (CWRU Astronomy) [note time] Tue. October 11th, 2016 11:00 am-12:00 pm *Note that the seminar may be pushed back to 11:30-12:30. The Radial Acceleration Relation in Rotationally Supported Galaxies We report a correlation between the radial acceleration traced by rotation curves and that predicted by the observed distribution of baryons. The same relation is followed by 2693 points in 153 galaxies with very different morphologies, masses, sizes, and gas fractions. The correlation persists even when dark matter dominates. Consequently, the dark matter contribution is fully specified by that of the baryons. The observed scatter is small and largely dominated by observational uncertainties. This radial acceleration relation is tantamount to a natural law for rotating galaxies. Continue reading… Stacy McGaugh (CWRU Astronomy) [note time] Nayana Shah, University of Cincinnati, Manifestations of spin-orbit coupling and topology in out-of-equilibrium hybrid superconducting systems Mon. October 10th, 2016 12:45 pm-1:45 pm Recently there has been a lot of excitement generated by the possibility of realizing and detecting Majorana fermions within the arena of condensed matter physics and its potential implication for topological quantum computing.  Although already at the end of twentieth century emergent Majorana end-states were shown to exist in a theoretical model of spinless p-wave superconductor (Kitaev) chain, it was only a decade later that proposals to experimentally realize such a model emerged. These were motivated by the discovery of topological insulators that ushered a new era of so-called symmetry-protected topological phases but also stemmed from existent studies of hybrid superconductor-ferromagnet systems that form the basis of another highly active area of superconducting spintronics. Continue reading… Nayana Shah, University of Cincinnati, Manifestations of spin-orbit coupling and topology in out-of-equilibrium hybrid superconducting systems 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, Continue reading… John Monnier (University of Michigan) Zhaoning Song, University of Toledo,The Formation and Degradation of Metal Halide Perovskites Mon. September 26th, 2016 12:45 pm-1:45 pm Solar cells based on organic-inorganic metal halide perovskite materials, such as methylammonium lead iodide (CH3NH3PbI3), have been the subject of intense investigation during the past 5 years due to high power conversion efficiencies (>22%) and relatively low manufacturing costs. Never before has the field of photovoltaics (PV) seen such rapid and exciting progress. The results are surprising because various low-temperature, solution-based processing methods have been successful in fabricating high-efficiency devices. Nevertheless, much of the work in this area has focused on device performance optimization and there is a lack of basic understanding of underlying physics and chemistry. Without this understanding, Continue reading… Zhaoning Song, University of Toledo,The Formation and Degradation of Metal Halide Perovskites 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. Continue reading… Kurt Hinterbichler (CWRU Physics) Henriette Elvang (University of Michigan) Tue. September 20th, 2016 11:00 am-12:00 pm Scattering amplitudes and soft theorems I will give a pedagogical introduction to the spinor helicity formalism which provides a very efficient tool for studies of on-shell scattering amplitudes in 4 dimensions. The power of this formalism will be demonstrated in a new analysis of soft photon and soft graviton theorems. Continue reading… Henriette Elvang (University of Michigan) 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). Continue reading… Director: Peter Galison (Harvard). Movie. Note unusual end time. Bob Brown (CWRU) Tue. September 13th, 2016 11:00 am-12:00 pm Understanding Color-Kinematics Duality with a New Symmetry: From Radiation Zeros to BCJ I discuss a new set of symmetries obeyed by tree-level gauge-theory amplitudes involving at least one gluon. The symmetry acts as a momentum-dependent shift on the color factors of the amplitude. Using our previous development of radiation vertex expansions, we prove the invariance under this color-factor shift of the n -gluon amplitude, and in fact for any amplitudes involving at least one massless gauge boson and any number of massless or massive particles in arbitrary representations of the gauge group with spin zero, Continue reading… Bob Brown (CWRU) 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. Continue reading… Richard Schaller (Northwestern University). Not a physics colloquium but of potential interest to physicists. Note unusual location and time. Raymond Stora’ Last Discovery — Bryan Lynn (CWRU) Tue. September 6th, 2016 11:00 am-12:00 pm I will discuss Raymond Stora’s final work on new Ward-Takahashi Identities of U(1) gauge theory. Continue reading… Raymond Stora’ Last Discovery — Bryan Lynn (CWRU) Bryan Lynn (CWRU and University College London) Tue. September 6th, 2016 11:00 am-12:00 pm Raymond Stora’s last work Continue reading… Bryan Lynn (CWRU and University College London) Excursion Sets, Peaks and Other Creatures: Improved Analytical Models of LSS – Marcello Musso Tue. May 3rd, 2016 11:30 am-12:30 pm I will present recent developments in analytical methods to predict abundance, clustering, velocities and bias of Dark Matter halos. In the standard analytical approach, halos are identified either with sufficiently high peaks of the initial matter density field, or with the largest spheres enclosing a sufficiently high density. I will revise the physical assumptions leading to this standard picture, and show how a careful statistical implementation of the model of collapse (even in the simple spherically symmetric case) leads to a surprisingly rich structure. This allows to make simple – yet remarkably accurate – analytical predictions for halo statistics, a necessary ingredient on the road to precision cosmology. Continue reading… Excursion Sets, Peaks and Other Creatures: Improved Analytical Models of LSS – Marcello Musso Observation Of Interlayer Phonons in Transition Metal Dichalogenide Atomic Layers and Heterostructures – Rui He Mon. May 2nd, 2016 12:30 pm-1:30 pm Interlayer phonon modes in atomically thin transition metal dichalcogenide (TMD) heterostructures were observed for the first time. We measured the low-frequency Raman response of MoS2/WSe2 and MoSe2/MoS2 heterobilayers. We discovered a distinctive Raman mode (30 – 35 cm-1) that cannot be found in any individual monolayers (see Fig. 1). By comparing with Raman spectra of bilayer (2L) MoS2, 2L MoSe2 and 2L WSe2, we identified the new Raman mode as the layer breathing mode (LBM) arising from the perpendicular vibration between the two TMD layers. The LBM only emerges in bilayer regions with atomically close layer-layer proximity and clean interface. Continue reading… Observation Of Interlayer Phonons in Transition Metal Dichalogenide Atomic Layers and Heterostructures – Rui He Do We Understand the Universe – Raul Jimenez Tue. April 26th, 2016 11:30 am-12:30 pm Observations of the cosmos provide a valuable tool to study the fundamental laws of nature. The future generation of astronomical surveys will provide data for a sizeable fraction of the observable sky. This rich data set should provide the means to answer fundamental questions: what are the laws of physics at high energies in the Early Universe? What is the nature of neutrinos? What is dark matter? What is dark energy? Why are there baryons at all? In this talk I will review the current status, provide a roadmap for future prospects and discuss in detail how we might approach the task of extracting information from the sky to answer the above questions. Continue reading… Do We Understand the Universe – Raul Jimenez Do We Understand the Universe? – Raul Jimenez Tue. April 26th, 2016 11:30 am-12:30 pm Observations of the cosmos provide a valuable tool to study the fundamental laws of nature. The future generation of astronomical surveys will provide data for a sizeable fraction of the observable sky. This rich data set should provide the means to answer fundamental questions: what are the laws of physics at high energies in the Early Universe? What is the nature of neutrinos? What is dark matter? What is dark energy? Why are there baryons at all? In this talk I will review the current status, provide a roadmap for future prospects and discuss in detail how we might approach the task of extracting information from the sky to answer the above questions. Continue reading… Do We Understand the Universe? – Raul Jimenez 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, Continue reading… Of Bodies Changed to New Forms – Tim Atherton New Directions in Bouncing Cosmologies – Anna M. Ijjas Tue. April 19th, 2016 11:30 am-12:30 pm In this talk, I will discuss novel ideas to smooth and flatten the universe and generate nearly scale-invariant perturbations during a contracting phase that precedes a cosmological bounce. I will also present some recent work on the possibility of having well-behaved non-singular bounces. Continue reading… New Directions in Bouncing Cosmologies – Anna M. Ijjas The 17 Position Knob: Tuning Interactions With Rare Earths – Paul C. Canfield Mon. April 18th, 2016 12:30 pm-1:30 pm Physicists see the rare earth group of elements as a powerful tool for tuning the properties of materials. Choice or control of rare earths can be used to modify (i) the size of the unit cell, (ii) the size of the local moment and degree of coupling, (iii) the size and direction of magnetic anisotropy, (iv) the amount of entropy that can be removed at low temperatures, (v) the degree of band filling, and / or (vi) the degree of hybridization. In this seminar I will provide an overview and examples of how this region of the periodic table can be used to guide and inspire research into a wide swath of novel materials and ground states. Continue reading… The 17 Position Knob: Tuning Interactions With Rare Earths – Paul C. Canfield 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. Continue reading… Resonant Tunneling in a Dissipative Environment: Quantum Critical Behavior – Harold Baranger Mapping the Phase Diagram of a One-Dimensional Topological Superconductor – Sergey Frolov Mon. April 11th, 2016 12:30 pm-1:30 pm Download the abstract Tunneling spectroscopy measurements on one-dimensional superconducting hybrid materials have revealed signatures of Majorana fermions which are the edge states of a bulk topological superconducting phase. We couple strong spin-orbit semiconductor InSb nanowires to conventional NbTiN superconductors to obtain additional signatures of Majorana fermions and to explore the magnetic-field driven topological phase transition. With improved device fabrication, namely more transparent contacts to superconductors and stronger coupled gate electrodes, we are mapping out the phase diagram of the topological phase in the space of Zeeman energy and chemical potential, and investigating the apparent closing and re-opening of the superconducting gap. Continue reading… Mapping the Phase Diagram of a One-Dimensional Topological Superconductor – Sergey Frolov 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. Continue reading… Can Charge Qubits Compete with Spin Qubits for Quantum Information Processing? – HongWen Jiang Beyond Precision Cosmology – Licia Verde Tue. April 5th, 2016 11:30 am-12:30 pm The avalanche of data over the past 10-20 years has propelled cosmology into the “precision era”. The next challenge cosmology has to meet is to enter the era of accuracy. Because of the intrinsic nature of studying the Cosmos and the sheer amount of data available and coming, the only way to meet these challenges is by developing suitable and specific statistical techniques. The road from precision Cosmology to accurate Cosmology goes through statistical Cosmology. I will outline some open challenges and discuss some specific examples. Continue reading… Beyond Precision Cosmology – Licia Verde Nanoscopic Manipulation and Nanoimaging of Liquid Crystals – Charles Rosenblatt Mon. April 4th, 2016 12:30 pm-1:30 pm Liquid crystals present a remarkable array of fascinating physical phenomena, and are now a >200 billion dollar world-wide industry. As liquid crystals most often are housed in a closed cell or sit atop a substrate, the treatment of the substrate plays a pivotal role. For the past fifteen years we have developed and exploited scanning probe microscope techniques to manipulate the liquid crystal’s orientation and order parameter at a surface on length scales down to a few tens of nanometers, and performed optical imaging with volumetric resolution 1000 times better than confocal microscopy. In this talk I will present our experimental techniques at the nanoscale, Continue reading… Nanoscopic Manipulation and Nanoimaging of Liquid Crystals – Charles Rosenblatt Nanoscopic Manipulation and Nanoimaging of Liquid Crystals – Charles Rosenblatt Mon. April 4th, 2016 12:30 pm-1:30 pm Liquid crystals present a remarkable array of fascinating physical phenomena, and are now a >200 billion dollar world-wide industry. As liquid crystals most often are housed in a closed cell or sit atop a substrate, the treatment of the substrate plays a pivotal role. For the past fifteen years we have developed and exploited scanning probe microscope techniques to manipulate the liquid crystal’s orientation and order parameter at a surface on length scales down to a few tens of nanometers, and performed optical imaging with volumetric resolution 1000 times better than confocal microscopy. In this talk I will present our experimental techniques at the nanoscale, Continue reading… Nanoscopic Manipulation and Nanoimaging of Liquid Crystals – Charles Rosenblatt 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, Continue reading… Controlling Coherent Spins at the Nanoscale: Prospects for Practical Spin-Based Technology – Jesse Berezovsky New Approaches to Dark Matter – Justin Khoury Tue. March 29th, 2016 11:30 am-12:30 pm In this talk I will discuss a novel theory of superfluid dark matter. The scenario matches the predictions of the LambdaCDM model on cosmological scales while simultaneously reproducing the MOdified Newtonian Dynamics (MOND) empirical success on galactic scales. The dark matter and MOND components have a common origin, as different phases of a single underlying substance. This is achieved through the rich and well-studied physics of superfluidity. The framework naturally distinguishes between galaxies (where MOND is successful) and galaxy clusters (where MOND is not): due to the higher velocity dispersion in clusters, and correspondingly higher temperature, the DM in clusters is either in a mixture of superfluid and normal phases, Continue reading… New Approaches to Dark Matter – Justin Khoury Nanomaterials in Liquid Crystal Mediated Interactions – Rajratan Basu Mon. March 28th, 2016 4:00 pm-5:00 pm In liquid crystals (LC) the effect of nonmesogenic guest-nanoparticles on the LC’s bulk properties often rests on the molecular identification at the nanoscale in order to share and disseminate the information’ coded into the nanostructure of the nanoparticles. I will present two types of nanomaterials and their intriguing interactions with LCs. Graphene is a twodimensional crystalline carbon allotrope where carbon atoms are densely packed in a regular sp2- bonded atomic-scale hexagonal pattern. This graphene nanostructure can used to enhance the tilted smectic-C order in an LC, giving rise to a faster ferroelectric switching. The presence of graphene can improve the electro-optic response and decrease the rotational viscosity of an LC. Continue reading… Nanomaterials in Liquid Crystal Mediated Interactions – Rajratan Basu 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, Continue reading… Photophysics of Organic Materials: From Thin-Film Devices to Single Molecules and from Optoelectronics to Entomology – Oksana Ostroverkhova Calibration of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) Detectors – Madeline Wade Tue. March 22nd, 2016 11:30 am-12:30 pm Calibration is the critical link between the LIGO detectors and searches for gravitational-wave signals in LIGO data. The LIGO calibration effort involves constructing the external strain incident on each LIGO detector from the digitized readout of the LIGO photodetectors. The essential steps in calibration are the development of accurate models of the LIGO detectors, the digitization of these models, and the application of the calibration models to construct the external strain. The Advanced LIGO era has brought new complexities in accurately modeling the LIGO detectors as well as the challenge of producing calibrated external strain data in low-latency. This talk will give an overview of the Advanced LIGO calibration procedure, Continue reading… Calibration of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) Detectors – Madeline Wade New Probes of Large-scale CMB Anomalies – Simone Aiola Tue. March 15th, 2016 11:30 am-12:30 pm Inflation prescribes a homogenous and isotropic universe on large scales, and it generates density fluctuations which are expected to be spatially correlated over the whole Hubble volume. Such fundamental predictions have been tested with current Cosmic Microwave Background (CMB) data and found to be in tension with our — remarkably simple — ΛCDM model. Is it just a random fluke or a fundamental issue with the present model? In this talk, I will present new possibilities of using CMB polarization as a probe of the measured suppression of the large-scale temperature correlation function. I will also discuss the viability of using this new technique with present and upcoming data. Continue reading… New Probes of Large-scale CMB Anomalies – Simone Aiola APS March Meeting Mon. March 14th, 2016 12:30 pm-1:30 pm Continue reading… APS March Meeting Preview APS March Meeting Talks – Graduate Students Thu. March 10th, 2016 11:00 am-12:00 pm Sukrit Sucharitacul, Few-layer III-VI and IV-VI 2D semiconductor transistorsShuhao Liu, Imaging the long diffusion lengths of photo-generated carriers in mixed halide perovskite films Shuhao Liu, Imaging the long diffusion lengths of photo-generated carriers in mixed halide perovskite films Robert Badea, Magneto-optical mapping of the domain wall pinning potential in ferromagnetic films Robert Badea, Magneto-optical mapping of the domain wall pinning potential in ferromagnetic films Michael Wolf, Coupling a driven magnetic vortex to individual nitrogen-vacancy spins for fast, nanoscale addressability and coherent manipulation Michael Wolf, Coupling a driven magnetic vortex to individual nitrogen-vacancy spins for fast, Continue reading… Preview APS March Meeting Talks – Graduate Students FMR-Drive Pure Spin Transport in Metals and Magnetic Insulators – Fengyuan Yang Mon. March 7th, 2016 12:30 pm-1:30 pm Spintronics relies on the generation, transmission, manipulation, and detection of spin current mediated by itinerant charges or magnetic excitations. Ferromagnetic resonance (FMR) spin pumping is a powerful technique in understanding pure spin current. Building on the highquality Y3Fe5O12 (YIG) films grown by our sputtering technique and the large inverse spin Hall effect (ISHE) signals enabled by these films, we have characterized pure spin currents in several classes of materials with different magnetic structures, including: nonmagnetic (NM) metals, ferromagnetic (FM) metals, nonmagnetic insulators, and antiferromagnetic (AF) insulators. The spin Hall angles determined for a series of 3d, 4d, and 5d NM metals show that both atomic number and d-electron count play important roles in spin Hall physics. Continue reading… FMR-Drive Pure Spin Transport in Metals and Magnetic Insulators – Fengyuan Yang Joining Forces Against the Dark Side of the Universe: The Cosmic Microwave Background and the Large Scale Structure – Shirley Ho Fri. March 4th, 2016 12:30 pm-1:30 pm Despite tremendous recent progress, gaps remain in our knowledge of our understanding of the Universe. For example, we have yet pinned down the properties of dark energy, nor have we confirmed Einstein’s theory of Gravity at the largest scales. Current and upcoming large sky surveys of the cosmic microwave background, large scale structure in galaxies, quasars, lyman-alpha forest and 21cm presents us with the best opportunity to understand various mysterious properties of the Universe and its underlying principles. I will review recent results from the Baryon Oscillations Spectroscopic Survey (BOSS). These results have demonstrated the feasibility of high precision Baryon Acoustic Oscillation (BAO) measurement, Continue reading… Joining Forces Against the Dark Side of the Universe: The Cosmic Microwave Background and the Large Scale Structure – Shirley Ho 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. Continue reading… Gravitational Waves Discovered: The Recent Detection of an Ancient Binary Black Hole Merger – Leslie E. Wade Tailored Radiative Processes of Quantum Dots and 2D Materials – Maiken H. Mikkelsen Mon. February 29th, 2016 4:00 pm-5:00 pm Metal-dielectric nanocavities have the ability to tightly confine light to small mode volumes resulting in strongly increased local density of states. Placing fluorescing molecules or semiconductor materials in this region enables wide control of radiative processes including absorption and spontaneous emission rates, quantum efficiency, and emission directionality. In this talk, I will describe our recent experiments utilizing a tunable plasmonic platform where emitters are sandwiched in a sub-10-nm gap between colloidally synthesized silver nanocubes and a metal film. Utilizing dye molecules with an intrinsic long lifetime reveals spontaneous emission rate enhancements exceeding a factor of 1,000 while maintaining directional emission and high quantum efficiency [Akselrod et al. Continue reading… Tailored Radiative Processes of Quantum Dots and 2D Materials – Maiken H. Mikkelsen Aspects of Photonic Topological Insulators – Mikael Rechtsman Mon. February 22nd, 2016 12:30 pm-1:30 pm I will present the observation of the topological protection of light – specifically, a photonic Floquet topological insulator. Topological insulators (TIs) are solid-state materials that are insulators in the bulk, but conduct electricity along their surfaces – and are intrinsically robust to disorder. In particular, when a surface electron in a TI encounters a defect, it simply goes around it without scattering, always exhibiting – quite strikingly – perfect transmission. The structure is an array of coupled helical waveguides (the helicity generates a fictitious circularly-polarized electric field that leads to the TI behavior), and light propagating through it is ‘topologically protected’ Continue reading… Aspects of Photonic Topological Insulators – Mikael Rechtsman 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. Continue reading… Non-Linear Optics of Ultrastrongly Coupled Cavity Polaritons – Mike Crescimanno 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. Continue reading… Albert Michelson, the Michelson-Morley experiment, and the dichotomy between megaprojects and table-top science – Philip Taylor Testing Early Universe Physics with Upcoming Observations – Emanuela Dimastrogiovanni Wed. February 10th, 2016 12:30 pm-1:30 pm Cosmology has seen tremendous progress thanks to precision measurements and is bound to greatly benefit from upcoming Large Scale Structure and Cosmic Microwave Background data. I will point out a number of interesting directions. In particular, I discuss how the microphysics of inflation may be tested in galaxy surveys through “fossil” signatures originating from squeezed primordial correlations. I further elaborate on the constraining power of CMB spectral distortions on small-scale cosmological fluctuations and on particle decays in the very early Universe in relation to reheating. I also describe some of the possible constraints on inflation and reheating from future B-mode observations. Continue reading… Testing Early Universe Physics with Upcoming Observations – Emanuela Dimastrogiovanni New Paradigm for Physics Beyond the Standard Model – Pavel Fileviez Perez Tue. February 9th, 2016 11:30 am-12:30 pm The great desert hypothesis in particle physics defines the relation between the electroweak scale and the high scale where an unified theory could describes physics. In this talk we review the desert hypothesis and discuss the main experimental constraints from rare decays. We present a new class of theories for the TeV scale where the desert hypothesis is not needed. In this context one predicts the existence of new particles with baryon and lepton numbers called lepto-baryons. The implications for cosmology, collider experiments and the unification of forces are discussed. Continue reading… New Paradigm for Physics Beyond the Standard Model – Pavel Fileviez Perez Cosmology from the Megaparsec to the Micron – Amol Upadhye Fri. February 5th, 2016 12:30 pm-1:30 pm Two major challenges for cosmology over the next decade are to characterize the dark energy responsible for the cosmic acceleration and to weigh the neutrinos, the only Standard Model particles whose masses are not yet known. Part I of the presentation describes my ongoing work to understand the effects of massive neutrinos and evolving dark energy on the formation of large-scale structure. I include both effects in a redshift-space generalization of Time-RG perturbation theory, and establish its validity through comparison to N-body simulations. In Part II I discuss my previous work using stars and laboratory experiments to search for couplings between dark energy and Standard Model particles. Continue reading… Cosmology from the Megaparsec to the Micron – Amol Upadhye 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. Continue reading… A New Twist on Electromagnetism for Energy Conversion – Stephen Rand Massive and Partially Massless Gravity and Higher spins – Kurt Hinterbichler Tue. February 2nd, 2016 11:30 am-12:30 pm On de Sitter space, there exists a special value for the mass of a graviton for which the linear theory propagates 4 rather than 5 degrees of freedom, known as a partially massless graviton. If a satisfactory non-linear version of the theory can be found and coupled to known matter, it would have interesting properties and could solve the cosmological constant problem. I will review attempts at constructing such a theory and some no-go’s, and will describe a Vasiliev-like theory containing a tower of partially massless higher spins. Continue reading… Massive and Partially Massless Gravity and Higher spins – Kurt Hinterbichler Combined First-Principles Molecular Dynamics / Density-Functional Theory Study of Ammonia Oxidation on Pt(100) Electrode – Dmitry Skachkov Mon. February 1st, 2016 12:30 pm-1:30 pm A combined first-principles molecular dynamics/density functional theory study of the electrooxidation of ammonia is conducted to gain an atomic-level understanding of the electrocatalytic processes at the Pt(1 0 0)/alkaline solution interface and to probe the mechanistic details of ammonia electrooxidation on the metal surface. A systematic study of adsorption and relative stability of ammonia and the intermediate species on the Pt(1 0 0) surface as a function of potential is carried out and activation energy profiles for the mechanistic steps in the ammonia oxidation are presented. The reaction mechanism is potential dependent: the modeling study supports the Oswin and Salomon’s mechanism for moderate surface potentials (≥ +0.5 V vs. Continue reading… Combined First-Principles Molecular Dynamics / Density-Functional Theory Study of Ammonia Oxidation on Pt(100) Electrode – Dmitry Skachkov 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 Continue reading… The 2015 Science Nobel Prizes – What were they given for? – Kurt Runge (Chemistry), Jim Kazura (Physiology or Medecine), Andrew Tolley (Physics) Testing Eternal Inflation – Matthew Johnson Tue. December 8th, 2015 11:30 am-12:30 pm The theory of eternal inflation in an inflaton potential with multiple vacua predicts that our universe is one of many bubble universes nucleating and growing inside an ever-expanding false vacuum. The collision of our bubble with another could provide an important observational signature to test this scenario. In this talk I will summarize recent work providing a quantitative connection between the scalar field lagrangian underlying eternal inflation and the observational signature of bubble collisions. I will also summarize existing constraints and forecasts for future searches using CMB and LSS, as well as discuss the general relevance of this work for assessing fine-tuning problems in inflationary cosmology. Continue reading… Testing Eternal Inflation – Matthew Johnson Bigravity: Dead or Alive? – Adam Solomon Tue. December 1st, 2015 11:30 am-12:30 pm Spurred in large part by the discovery of the accelerating universe, recent years have seen tremendous advances in our understanding of alternatives to general relativity, particularly in the large-distance and low-curvature régimes. Looming large in this field is the recent development of a ghost-free, nonlinear theory of massive gravity and multimetric gravity (or equivalently, theories of interacting gravitons), which had proven elusive for the better part of seven decades. Nevertheless, both massive gravity and its generalization to a bimetric theory have run into potentially-deadly problems in the search for viable, self-accelerated cosmologies. I will summarize some of these issues, and then discuss possible ways out. Continue reading… Bigravity: Dead or Alive? – Adam Solomon Non-adiabatic Transport in Single-Electron Transistors in the Kondo Regime – Andrei Kogan Mon. November 23rd, 2015 12:30 pm-1:30 pm Magnetic impurities in conductors alter the Fermi sea: A many-body state (A Kondo singlet) is formed that entangles itinerant carriers and the impurity site. This causes a sharp rearrangement of the density of states near the Fermi surface into a hierarchical set governed by a single energy parameter Tk, the Kondo temperature. Equilibrium physics of such electronic “knots” scales with Tk and is highly universal: impurities that differ microscopically from one another yet have similar Kondo temperatures produce Kondo states with similar properties. Recent studies of Kondo physics with voltage-controllable spin traps known as Single-Electron Transistors (SETs) have focused on nonequiibrium Kondo phenomena, Continue reading… Non-adiabatic Transport in Single-Electron Transistors in the Kondo Regime – Andrei Kogan 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. Continue reading… Gravitational wave detection with precision interferometry – Nergis Malvalvala (unofficial colloquium) Chip-integrated Nanophotonic Structures for Classical and Quantum Devices – Antonio Badolato Mon. November 16th, 2015 12:30 pm-1:30 pm Chip-integrated nanophotonics investigates the interaction of light with nanostructures integrated on a chip. Lying at the intersection of condensed matter physics, optics, nanotechnology, and materials science, nanophotonics draws upon expertise from broad areas of physics and engineering, while presenting major opportunities to advance fundamental physics and transformative photonic technologies. In this talk, I will focus on our experimental research in two areas of nanophotonics. First, I will show that nanostructured semiconductors, such as quantum dot heterostructures coupled to photonic crystal nanocavities, can now offer First, I will show that nanostructured semiconductors, such as quantum dot heterostructures coupled to photonic crystal nanocavities, Continue reading… Chip-integrated Nanophotonic Structures for Classical and Quantum Devices – Antonio Badolato Ultra-low field MRI – Michael Hatridge Fri. November 13th, 2015 12:30 pm-1:30 pm Superconducting Quantum Interference Devices (SQUIDs), consisting of two Josephson junctions in a closed superconducting loop, are exquisitely sensitive detectors of magnetic flux. In recent years, we have built magnetic resonance imaging (MRI) scanners based around these detectors which are capable of in vivo imaging at ultra-low (132 microTesla) fields, rather than the several Tesla of conventional MRI. I’ll discuss the challenges and unique advantages of ultra-low field MRI, including enhanced contrast between tissues types such as normal and cancerous prostate tissue which are nearly identical at high fields. Continue reading… Ultra-low field MRI – Michael Hatridge 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. Continue reading… Remote entanglement in superconducting quantum information – Michael Hatridge 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. Continue reading… Remote entanglement in superconducting quantum information – Michael Hatridge Josephson junctions and quantum microwave circuits 2: amplifiers – Michael Hatridge Tue. November 10th, 2015 11:30 am-12:30 pm Here we will take the concepts from lecture one and set out to construct from the same Josephson junctions very weakly non-linear circuits which operate as phase-preserving amplifiers. I’ll discuss some of the numerous chall enges in designing superconducting amplifiers which are robust and simple while achieving nearly ideal performance. I’ll also discuss the quantum-limit of amplification, how closely we can approach it, and how such amplifiers allow precision readout of our quantum bits. Continue reading… Josephson junctions and quantum microwave circuits 2: amplifiers – Michael Hatridge Michelson Postdoc Lecture – Michael Hatridge Mon. November 9th, 2015 12:30 pm-1:30 pm Continue reading… Michelson Postdoc Lecture – Michael Hatridge Josephson junctions and quantum microwave circuits 1: qubits and cavities – Michael Hatridge Mon. November 9th, 2015 12:30 pm-1:30 pm In this lecture I’ll review the basics of the Josephson junction and how it is used as the key building block in superconducting quantum information. I’ll show how we build coupled circuits consisting of a rather non-linear oscillator (which we use as our qubit) coupled to an (almost) linear oscillator/cavity which both shelters the qubit from the outside environment and allows for qubit control and quantum-non-demolition readout. Continue reading… Josephson junctions and quantum microwave circuits 1: qubits and cavities – Michael Hatridge 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. Continue reading… Intracellular Pressure Dynamics in Cells – Wanda Strychalski Supercooling-Driven Glass Behaviour in Systems Exhibiting Continuous Symmetry Breaking – Sami Kralj Wed. November 4th, 2015 12:30 pm-1:30 pm Symmetry breaking is ubiquitous in nature and represents the key mechanism behind rich diversity of patterns exhibited by nature. One commonly introduces an order parameter field to describe onset of qualitatively new ordering in a system on varying a relevant control parameter driving a symmetry breaking transition. In case of continuous symmetry breaking an order parameter consists of two qualitatively different components: an amplitude and gauge field. The latter component enables energy degeneracy and reveals how symmetry is broken. Inherent degeneracy could in general lead to nearby regions exhibiting significantly different gauge fields. Resulting frustrations can nucleate topological defects (TDs) [1]. Continue reading… Supercooling-Driven Glass Behaviour in Systems Exhibiting Continuous Symmetry Breaking – Sami Kralj 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. Continue reading… Enabling High Performance Computational Physics with Community Libraries – Matt Knepley Bi-gravity from DGP Two-brane Model – Yasuho Yamashita Wed. October 28th, 2015 12:30 pm-1:30 pm We discuss whether or not bigravity theory can be embedded into the braneworld setup. As a candidate, we consider Dvali-Gabadadze-Porrati two-brane model. We will show that we can construct a ghost free model whose low energy spectrum is composed of a massless graviton and a massive graviton with a small mass, fixing the brane separation with the Goldberger-Wise radion stabilization. We also show that there is two branches: the normal branch is stable and the self-accelerating branch is inevitably unstable, and discuss the condition for the normal branch. Next, we consider DGP two-brane model without the radion stabilization to discuss how the ghost free bigravity coupled with a single scalar field can be derived from a braneworld setup. Continue reading… Bi-gravity from DGP Two-brane Model – Yasuho Yamashita The Instability of de Sitter Space and Dynamical Dark Energy: Massless Degrees of Freedom from the Conformal Anomaly in Cosmology – Emil Mottola Tue. October 27th, 2015 11:30 am-12:30 pm Global de Sitter space is unstable to particle creation, even for a massive free field theory with no self-interactions. The Bunch-Davies state is a definite phase coherent superposition of particle and anti-particle solutions in both the asymptotic past and future, and therefore is not a true vacuum state. In the closely related case of particle creation by a constant, uniform electric field, a time symmetric state analogous to the de Sitter invariant one is constructed, which is also not a stable vacuum state. The conformal anomaly plays a decisive role in the growth of perturbations and de Sitter symmetry breaking. Continue reading… The Instability of de Sitter Space and Dynamical Dark Energy: Massless Degrees of Freedom from the Conformal Anomaly in Cosmology – Emil Mottola Photogeneration and Charge Transport in Liquid Crystalline Organic Semiconductors – Sanjoy Paul Mon. October 26th, 2015 12:30 pm-1:30 pm Organic semiconductors (OSCs) are emerging candidates for the applications in electronic and photonic devices due to material’s low cost and ease of processing. Many materials have been studied to understand the charge generation and transport physics, as well as to develop techniques for facile processing into light emitting diodes, thin film transistors, photovoltaics, and host of other devices. A recurring theme in this effort is the role of disorder in determining critical material parameters, such as mobility and photogeneration efficiency. A particularly useful class of materials in this quest is that of liquid crystalline (LC) OSCs. LCOSCs offer many advantages including facile alignment and the opportunity to study the effects of differing intermolecular geometries on transfer integrals, Continue reading… Photogeneration and Charge Transport in Liquid Crystalline Organic Semiconductors – Sanjoy Paul 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. Continue reading… Quantum Chromodynamics at Five Trillion Degrees Kelvin – Michael Strickland Spins in 2D Materials – Roland Kawakami Mon. October 19th, 2015 12:30 pm-1:30 pm Two-dimensional crystals such as graphene and monolayer transition metal dichalcogenides (TMD) possess unique properties not found in bulk materials. These materials are atomically-thin, yet are strong enough to remain intact as free standing membranes. Because these materials are “all surface”, they tend to be highly surface sensitive and amenable to inducing proximity effects. In this talk, I will discuss our progress of investigating spin-dependent phenomena in graphene and TMD monolayers. We investigate spin transport in graphene utilizing ferromagnetic electrodes to inject and detect In this talk, I will discuss our progress of investigating spin-dependent phenomena in graphene and TMD monolayers. Continue reading… Spins in 2D Materials – Roland Kawakami 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. Continue reading… In honor of Ben Segall’s 90th birthday – Arnold Dahm, Philip Taylor, Walter Lambrecht Perspectives on WIMP Dark Matter – Pearl Sandick Tue. October 13th, 2015 11:30 am-12:30 pm The question of the identity of dark matter remains one of the most important outstanding puzzles in modern physics. Weakly Interacting Massive Particles (WIMPs) have long been the frontrunner dark matter candidate, with the supersymmetric neutralino serving as the canonical WIMP. In this talk, I’ll discuss recent results relevant to the search for dark matter, supersymmetric and otherwise, and highlight the spectrum of theoretical and phenomenological approaches to its study. From fundamental constructions to simplified models and effective theories, each approach plays a specific role in furthering our understanding and allowing us to evaluate the prospects for discovery of dark matter. Continue reading… Perspectives on WIMP Dark Matter – Pearl Sandick Static and Dynamic Flowers in Strained Graphene – Nancy Sandler Mon. October 12th, 2015 12:30 pm-1:30 pm The coupling of geometrical and electronic properties is a promising venue to engineer conduction properties in graphene. In particular, different regimes can be achieved by manipulating confinement and strain fields, as shown in recent experiments on nanobubbles, drumheads oscillating membranes, and narrow strips deposited on patterned SiC substrates [1]. To investigate strain signatures on graphene systems, we focus on a simple model with a circularly symmetric out-of-plane deformation. Results from numerical tight-binding and Dirac-continuum models for a static deformation reveal intriguing flower-shaped structures in the local density of states with profound consequences for charge transport through the structure [2]. Continue reading… Static and Dynamic Flowers in Strained Graphene – Nancy Sandler The Standard Model of Particle Physics via Non-Commutative Geometry – Latham Boyle Fri. October 9th, 2015 12:30 pm-1:30 pm I will introduce Connes’ notion of non-commutative geometry, and explain how it offers a novel geometric perspective on certain otherwise unexplained features of the standard model of particle physics, and a more restrictive framework than effective field theory for exploring physics beyond the standard model. I will also explain the main ideas behind a new reformulation of NCG which has certain key mathematical and physical advantages over Connes’ traditional “spectral triple” formulation. In this reformulation, the traditional NCG axioms are considerably simplified and unified; a number of problematic issues in the traditional NCG construction of the standard model are fixed; Continue reading… The Standard Model of Particle Physics via Non-Commutative Geometry – Latham Boyle The Status and Challenges of Lead Halide Perovskite Solar Cells – Yanfa Yan Mon. October 5th, 2015 12:30 pm-1:30 pm Organic-inorganic methylammounium lead halide perovskites, CH3NH3PbX3 (X= Cl, Br, I), have revolutionized the field of thin-film solar cells. Within five years, the efficiency of lead halide perovskite-based thin-film solar cells have increased rapidly from 3.8% in 2009 to 20.1% for a planar CH3NH3PbI3-based thin-film solar cell in 2014. Such rapid progress has never been seen before in the history of solar cell development. In this talk, I will review the history and status of lead halide perovskite thin films solar cells. I will explain why lead halide perovskites exhibit superior photovoltaic properties that conventional solar cell materials such as Si, Continue reading… The Status and Challenges of Lead Halide Perovskite Solar Cells – Yanfa Yan 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. Continue reading… The Conformal Bootstrap: From Magnets to Boiling Water – David Simmons-Duffin An Anisotropic Universe Due to Dimension-changing False Vacuum Decay – James Scargill Tue. September 29th, 2015 11:30 am-12:30 pm In this talk I will consider the observational consequences of models of inflation after false vacuum decay in which the parent vacuum has a smaller number of large dimensions than our current vacuum. After introducing and briefly discussing in general the topic of inflation after false vacuum, I will then explain how such events can occur which change the number of large dimensions and lead to an anisotropic universe. The effects on the CMB of anisotropy at late times might be expected to render irrelevant the effects of primordial anisotropy, however after showing how to properly deal with the latter I will demonstrate how for the tensor perturbation modes the primordial effects are much larger than expected and can in fact be dominant. Continue reading… An Anisotropic Universe Due to Dimension-changing False Vacuum Decay – James Scargill Device-compatible Defect Engineering of Rare Earth Doped Nitrides – Volkmar Dierolf Mon. September 28th, 2015 12:30 pm-1:30 pm LED-lighting is at the verge of replacing conventional incandescent light sources. These white LEDs are based on nitride technology which produces the blue emission, that is subsequently converted in a separate phosphorescent layer to provide the additional required colors. The latter often consists of an insulating material doped with rare earth ions. In order to facilitate further integration, the possibility of introducing rare earth ions directly into the nitride material has been explored, with considerable success. Doping with europium ions (Eu) is of particular interest since they can produce the red color, which remains a challenge for nitride based materials. Continue reading… Device-compatible Defect Engineering of Rare Earth Doped Nitrides – Volkmar Dierolf 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. Continue reading… Who and where is the graviton? – Claudia de Rham Prospects for Measuring the Neutron-star Equation of State with Advanced Gravitational-wave Detectors – Leslie Wade Tue. September 22nd, 2015 11:30 am-12:30 pm It is widely anticipated that the first direct detections of gravitational waves will be made by advanced gravitational-wave detectors, such as the two Laser Interferometer Gravitational-wave Observatories (LIGO) and the Virgo interferometer. Arguably the most important source for ground-based interferometers are coalescing binary neutron stars. Following the detection of such a system, a more detailed followup analysis will seek to measure certain properties of the component neutron stars, such as their masses and/or spin configurations. In particular, it has been shown that the gravitational waves emitted by binary neutron stars carry information about the neutron-star equation of state. In this talk, Continue reading… Prospects for Measuring the Neutron-star Equation of State with Advanced Gravitational-wave Detectors – Leslie Wade Quantum Magnetism in Low Dimensions: An Intriguing Phenomenon Connecting Biology with Physics – Yi-Kuo Yu Mon. September 14th, 2015 12:30 pm-1:30 pm Magnetism is an important problem in many areas of science including biology, physics and material science. For example, many migratory animals (birds, whales and sea turtles) use magnetism to sense direction for their migrations; computer hard drives store information via magnetism; and so forth. Quantum magnetism in low-dimensional systems plays a particularly important role in biophysical systems within which magnetic moments of different sizes might be useful for different purposes. In this perspective, the role of magnetism with higher magnetic moments is relatively less understood. To gain a better understanding for magnetism encompassing low and high moments, we studied a quantum mechanical spin lattice system consisting of one-dimensional anti-ferromagnetic Heisenberg chain of spin s embedded in a three dimensional lattice. Continue reading… Quantum Magnetism in Low Dimensions: An Intriguing Phenomenon Connecting Biology with Physics – Yi-Kuo Yu 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? Continue reading… The Science of Climate Change and the Changing Climate of Science – Philip Taylor Buckling Instabilities and Recoil Dynamics in Free-Standing Liquid Crystal Filaments – Tanya Ostapenko Mon. May 18th, 2015 12:30 pm-1:30 pm Quasi-one-dimensional free-standing fluid structures are not often found in nature, but may be formed by any material that can overcome capillary instability. Once this instability is suppressed, long filaments, with a length-to-diameter ratio greater than ï¿½, may form. Liquid crystals are an extraordinary system that can form free-standing fluid filaments with length-to-diameter ratios exceeding 7000. Buckling instabilities in freestanding liquid crystal filaments formed from bent-core liquid crystals in the B7 phase may be induced in a variety of ways, e.g. by acoustical or electrical vibration. However, this talk will focus on instabilities induced by compressing the filament, as well as those from a mechanical or thermal rupture. Continue reading… Buckling Instabilities and Recoil Dynamics in Free-Standing Liquid Crystal Filaments – Tanya Ostapenko Quantum Phase Transitions in Magnets – Ribhu Kaul Mon. May 11th, 2015 12:30 pm-1:30 pm Continue reading… Quantum Phase Transitions in Magnets – Ribhu Kaul 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. Continue reading… Cosmology with Planck’s Observations of the Cosmic Microwave Background – Brendan Crill Gravitational Signals from Noise in the Hubble Diagram – Edward Macaulay Tue. May 5th, 2015 11:30 am-12:30 pm Understanding the nature of the dark universe requires precise measurements of the background expansion history, and also the growth rate of density fluctuations. In this talk, I’ll consider both regimes with supernova lensing for the OzDES spectroscopic survey – which is measuring the redshifts of hundreds of supernova and thousands of galaxies identified by the Dark Energy Survey. I’ll start by reviewing the more established method of growth rate measurements with Redshift Space Distortions, and discuss possible tension between RSDs and expectations from Planck CMB measurements. I’ll then consider how OzDES can place novel constraints on the growth rate and amplitude of density fluctuations by correlating noise in the supernova Hubble diagram with the gravitational effects of lensing and peculiar velocities expected from the observed density field. Continue reading… Gravitational Signals from Noise in the Hubble Diagram – Edward Macaulay 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, Continue reading… One century of neutrino mass experiments: from radium salts to microwaves – Benjamin Monreal A career in clean energy – Philip Farese Thu. April 23rd, 2015 11:30 am-12:30 pm Continue reading… A career in clean energy – Philip Farese Thank You for Flying the ‘Vomit Comet’: Using Parabolic Flights to Examine Quantitatively the Stability of Liquid Bridges Under Varying Total Body Force – Greg DiLisi Mon. April 20th, 2015 12:30 pm-1:30 pm Liquid bridges were flown aboard a Boeing 727-200 aircraft in a series of parabolic arcs that produced multiple periods of microgravity. During the microgravity portion of each arc, g_eff , the effective total body acceleration due to external forces became negligibly small so that cylindrical liquid bridges could be suspended across two coaxial support posts. Near the bottom of each arc, g_eff slowly increased to a maximum of 1.84g, causing the liquid bridges to deform and in some cases collapse. Although the physics of liquid bridges subject to varying total body force is well-established and has been analyzed extensively both theoretically and experimentally, Continue reading… Thank You for Flying the ‘Vomit Comet’: Using Parabolic Flights to Examine Quantitatively the Stability of Liquid Bridges Under Varying Total Body Force – Greg DiLisi 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. Continue reading… Novel measurement methods for probing magnetic nanoparticles – Yumi Ijiri 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. Continue reading… Stochasticity in ecological dynamics – Karen Abbott The Race for the Highest Energy Neutrinos in the Universe – Patrick Allison Tue. April 7th, 2015 11:30 am-12:30 pm In 1969, Berezinsky and Zatsepin predicted a flux of ultra-high energy (greater than 1 EeV) neutrinos due to cosmic ray interactions with the cosmic microwave background. These ‘cosmogenic’ BZ neutrinos are virtually “guaranteed” – barring extreme changes in either fundamental physics or our understanding of the source of cosmic rays, these neutrinos must exist. Detecting these neutrinos is extremely challenging, due to their incredibly low flux – however, recent experiments are approaching the sensitivity needed to finally make a detection. Here, I will talk about several of these existing and upcoming experiments, including the ANITA and EVA balloon-borne detectors, and the ARA experiment, Continue reading… The Race for the Highest Energy Neutrinos in the Universe – Patrick Allison 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. Continue reading… Music, Sweet and Sour – David Farrell Macro Dark Matter – David Jacobs Tue. March 31st, 2015 11:30 am-12:30 pm Dark matter is a vital component of the current best model of our universe, Lambda-CDM. There are leading candidates for what the dark matter could be (e.g. weakly-interacting massive particles, or axions), but no compelling observational or experimental evidence exists to support these particular candidates, nor any beyond-the-Standard-Model physics that might produce such candidates. This suggests that other dark matter candidates, including ones that might arise in the Standard Model, should receive increased attention. I will discuss the general class of dark matter candidates with characteristic masses and interaction cross-sections characterized in units of grams and square centimeters, respectively — Continue reading… Macro Dark Matter – David Jacobs V2O5, a Strongly Correlated 2D System with 1D Aspects – Walter Lambrecht Mon. March 30th, 2015 12:30 pm-1:30 pm V2O5 is a layered material with chains within the layer. I will discuss how this is manifested in its electronic band structure. The quasiparticle self-consistent GW method in this material strongly overestimates the band gap. The main reasons for this are examined and found to be a lattice polarization contribution to the screening of the electron-electron interaction. This is related to the large LO/TO phonon splittings in this material. Changes in band structure and phonons between bulk and monolayer will be discussed. Continue reading… V2O5, a Strongly Correlated 2D System with 1D Aspects – Walter Lambrecht 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, Continue reading… Multiscale Self-organization of Emulsion Droplets – Jasna Brujic Wave Turbulence in Preheating – Henrique de Oliveira Tue. March 24th, 2015 11:30 am-12:30 pm We have studied the nonlinear preheating dynamics of several inflationary models. They include nonminimally coupled scalar fields and two-fields models. It is well established that after a linear stage of preheating characterized by the parametric resonance, the nonlinear dynamics becomes relevant driving the system towards turbulence. Wave turbulence is the appropriated description of this phase since the matter contents are fields instead of usual fluids. Turbulence develops due to the nonlinear interations of waves, here represented by the small inhomogeneities of the scalar fields. We present relevant aspects of wave turbulence and presented the effective equation of state at the thermalize phase. Continue reading… Wave Turbulence in Preheating – Henrique de Oliveira Predictive First-principles Simulations of Excited Electrons and Ultrafast Electron-ion Dynamics in Complex Materials – Andre Schleife Mon. March 23rd, 2015 12:30 pm-1:30 pm Rapidly advancing high-performance super computers such as “Blue Waters” allow calculating properties of increasingly complex materials with unprecedented accuracy. In order to fully take advantage of leadership-class machines and to accurately describe modern materials, codes need to scale well on hundreds of thousands of processors. This talk focuses on electronic excitations and their ultrafast attosecond dynamics that are notoriously difficult to capture due to the quantum-mechanical electron-electron interaction. Being omnipresent in electronic and optical materials, an accurate description is a crucial factor for computational design of materials for technological applications. It will be outlined how cutting-edge first-principles techniques based on many-body perturbation theory accomplish predictive theoretical spectroscopy of electronic excitations e.g. Continue reading… Predictive First-principles Simulations of Excited Electrons and Ultrafast Electron-ion Dynamics in Complex Materials – Andre Schleife Interacting particle models and phase transitions for social particles – Alethea Barbaro Thu. March 19th, 2015 4:15 pm-5:15 pm Continue reading… Interacting particle models and phase transitions for social particles – Alethea Barbaro Graphene on Ir(111), Adsorption and Intercalation of Cs and Eu Atoms – Pedrag Lazic Mon. March 16th, 2015 12:30 pm-1:30 pm Experimental and theoretical study of Cs and Eu atoms adsorption on graphene on Ir(111) will be presented [1,2]. Graphene on Ir(111) surface is an interesting system because graphene has almost pristine electronic structure in it due to its weak bonding character to iridum surface. The bonding is almost exclusively of the van der Waals type. However adding Cs or Eu atoms graphene gets doped and and nature of binding changes – especially in the case when the atoms intercalate. Density Functional Theory calculations with standard semilocal functionals (GGA) – fail to reproduce experimental findings even qualitatively. Only when the newly developed nonlocal correlation functional is used (vdW-DF) which includes van der Waals interactions, Continue reading… Graphene on Ir(111), Adsorption and Intercalation of Cs and Eu Atoms – Pedrag Lazic 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. Continue reading… Opportunities and Challenges for Extreme Optics – Nader Engheta March Meeting Preview Talks – Graduate Students Mon. February 23rd, 2015 12:30 pm-1:45 pm APS March Meeting 2015 graduate student talks Jiayuan Miao: Molecular-dynamics study of the Case-II diffusion of methanol in PMMA Sukrit Sucharitakul: Field effect vs. Hall mobility in back-gated multilayered InSe FETs Nicholas J. Goble: Effects of structural phase transitions on the interface of perovskite oxides Bin Liu: Ultrastrong exciton-photon coupling in single and coupled organic microcavities Ittipon Fongkaew: Electric field and spin-orbit coupling effects on the band structure of monolayer WSe2 Continue reading… March Meeting Preview Talks – Graduate Students Mapping New Physics with the Cosmic Microwave Background – Jeff McMahon Mon. February 23rd, 2015 11:30 am-12:30 pm The Cosmic Microwave Background (CMB) is the afterglow of the big bang and the oldest light in the universe that can be observed. Faint signals in the pattern of the CMB provide information about the physics that govern the very early universe and the growth of large scale structure. Thus, precision measurements of the CMB provide unique views on ultra high energy physics (inflation); pressing mysteries including dark energy and dark matter; and traditional particle physics questions such as the sum of the neutrino masses. In this talk I present the state of the CMB field and highlight the Atacama Cosmology Telescope Polarimeter (ACTPol) and it successor Advanced ACTPol (AdvACT). Continue reading… Mapping New Physics with the Cosmic Microwave Background – Jeff McMahon Optical Frequency Combs and Precision Spectroscopy – Jason Stalnaker Tue. February 17th, 2015 11:30 am-12:30 pm Atomic spectroscopy has a long history of providing tests of fundamental physics. This tradition continues as the precision and accuracy of spectroscopic techniques improve. I will discuss the impact that the development of stabilized optical frequency combs has had on precision spectroscopy and describe an ongoing effort to study the atomic spectra of lithium at Oberlin College. Continue reading… Optical Frequency Combs and Precision Spectroscopy – Jason Stalnaker Exploring Soft Matter with DNA – Tomasso Bellini Mon. February 16th, 2015 12:30 pm-1:30 pm The combination of solubility, coded pairing and adjustable flexibility make DNA a unique polymer for designing highly-controlled self-assembled complex nanostructures and novel materials. The same tools can be exploited to produce DNA-based systems enabling the exploration of challenging topics in soft matter physics. In the talk I will exemplify this approach by describing experiments and results in which DNA assembly was used to study living polymerization, liquid crystal ordering, the templating of chemical reactions, and phase behavior and gelation transition of low-valence colloidal particles. Continue reading… Exploring Soft Matter with DNA – Tomasso Bellini Numerical Relativity in Spherical Polar Coordinates – Thomas W. Baumgarte Thu. February 12th, 2015 11:30 am-12:30 pm Numerical relativity simulations have made dramatic advances in recent years. Most of these simulations adopt Cartesian coordinates, which have some very useful properties for many types of applications. Spherical polar coordinates, on the other hand, have significant advantages for others. Until recently, the new coordinate singularities in spherical polar coordinates have hampered the development of numerical relativity codes adopting such coordinates, at least in the absence of symmetry assumptions. With a combination of different techniques – a reference-metric formulation of the relevant equations, a proper rescaling of all tensorial quantities, and a partially-implicit Runge-Kutta method – we have been able to solve these problems. Continue reading… Numerical Relativity in Spherical Polar Coordinates – Thomas W. Baumgarte 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? Continue reading… Chemistry in Art, Art in Chemistry, and the Spiritual Ground They Share – Roald Hoffmann The Chirality of SiO4 in Materials – David Avnir Wed. February 11th, 2015 12:30 pm-1:30 pm SiO4 is a common building block of many materials, both crystalline such as quartz, silicates and zeolites, and amorphous, such as silica. Although intuitively one would think that SiO4 is an achiral perfect tetrahedron, in the vast majority of silicon-oxide based materials, that tetrahedron is of lower symmetry, to the degree of being chiral. Discussion of the chirality of SiO4 and its manifestation in crystalline and amorphous materials, will be the main focus of this lecture. Specific topics to be covered include the induction of chirality in silicas; the contribution of randomness to the emergence of chirality; the chirality of zeolites and silicates; Continue reading… The Chirality of SiO4 in Materials – David Avnir 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, Continue reading… Teaching old materials new tricks: Making organic semiconductors crystallize on demand and metals emit light – Barry Rand Is Clustering Dark Energy Non-linear? The AP Resummation Approach – Stefano Anselmi Tue. February 3rd, 2015 11:30 am-12:30 pm In order to gain insights on the mysterious component driving the acceleration of the Universe the future surveys will measure with unprecedent precision the density power spectrum in the non-linear range of scales and redshifts. On the theoretical hand those non-linearities require a comparable computational level. This is a tremendous effort that see deployed numerical (N-body), semi-analytical and analytical investigations. I this context I will present a powerful analytical resummation scheme first developed for LCDM and very recently extended to the Clustering Quintessence scenario, i.e. quintessence models with vanishing speed of sound. The approach I will expose allows predictions at few percent level beyond the Baryon Acoustic Oscillations range of scales, Continue reading… Is Clustering Dark Energy Non-linear? The AP Resummation Approach – Stefano Anselmi Spin-dependent Scattering in Graphene: Electronic Birefringence and Kondo Transitions – Sergio Ulloa Mon. February 2nd, 2015 12:30 pm-1:30 pm Graphene, a monoatomic layer of carbon, is perhaps the simplest and most easily available material where electrons behave as massless Dirac particles. Apart from the many promising technological applications, the study of graphene (and other layered materials) has opened a number of interesting theoretical questions: the microscopic crystalline structure requires an additional degree of freedom (the pseudo spin) that gives rise to effects such as the Klein paradox or Veselago electron lenses. The spin-orbit interaction (SOI) in materials arises from intrinsic lack of inversion symmetry in the lattice structure or from external or interfacial fields that break spatial symmetries. Although SOI is weak in natural graphene, Continue reading… Spin-dependent Scattering in Graphene: Electronic Birefringence and Kondo Transitions – Sergio Ulloa 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”. Continue reading… 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. Sterile Plus Active Neutrinos and Neutrino Oscillations – Leonard Kisslinger Mon. January 26th, 2015 12:30 pm-1:30 pm The talk will be based on recent neutrino oscillation experiments that have determined that there is almost certainly a sterile neutrino, with an estimate of the mixing angle. Continue reading… Sterile Plus Active Neutrinos and Neutrino Oscillations – Leonard Kisslinger 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? Continue reading… Physics of the Piano – Nicholas Giordano New Accelerators for Neutrino Physics – Matt Toups Tue. January 20th, 2015 11:30 am-12:30 pm DAEδALUS is a proposed phased neutrino experiment, whose ultimate aim is to search for evidence of CP violation in the neutrino sector. The experiment will consist of several accelerator-based modules that produce decay-at-rest neutrino beams located at three different distances from a single, large underground neutrino detector. Each of these modules will make use of a pair of low-cost, high power cyclotrons to accelerate an H2+ beam initially up to 60 MeV with a compact injector cyclotron and then ultimately up to 800 MeV with a separated sector super-conducting cyclotron. These new low-cost, high power cyclotrons are motivated by industry needs and also open up new possibilities for searches for physics beyond the standard model with neutrinos. Continue reading… New Accelerators for Neutrino Physics – Matt Toups 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. Continue reading… Cooperation, cheating, and collapse in biological populations – Jeff Gore The Break-up of Viscoelastic Jets and Filaments: The Beads-on-a-string Structure – Marie-Charlotte Renoult Mon. December 1st, 2014 12:30 pm-1:30 pm Capillary pressure can destabilize a thin stream of water and break it up into a succession of small droplets. The addition of a minute quantity (some part per million) of a long, flexible and water-soluble polymer is enough to modify the growth and morphology of this instability and leads, close to breakup, to the development of Beads-on-a-string structures (BOAS) where droplets are connected by thin threads. The BOAS phenomenon is also observed after stretching a bridge of a viscoelastic liquid. Experiments on jets and stretched bridges of viscoelastic polymeric solutions were conducted to gain more insight into the formation and time evolution of the BOAS in both configurations. Continue reading… The Break-up of Viscoelastic Jets and Filaments: The Beads-on-a-string Structure – Marie-Charlotte Renoult The Universe as a Cosmic String – Florian Niedermann Tue. November 25th, 2014 11:30 am-12:30 pm We are investigating modifications of general relativity that are operative at the largest observable scales. In this context, we are investigating the model of brane induced gravity in 6D, a higher dimensional generalization of the DGP model. As opposed to different claims in the literature, we have proven the quantum stability of the theory in a weakly coupling regime on a Minkowski background. In particular, we have shown that the Hamiltonian of the linear theory is bounded from below. This result opened a new window of opportunity for consistent modified Friedmann cosmologies. In our recent work it is shown that a brane with FRW symmetries necessarily acts as a source of cylindrically symmetric gravitational waves, Continue reading… The Universe as a Cosmic String – Florian Niedermann 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, Continue reading… Spotting Majorana Fermions amidst Hofstadter butterflies and disordered landscapes – Smita Vishveshwara Imprints of the Standard Model in the Sky? – Daniel G. Figueroa Tue. November 18th, 2014 11:30 am-12:30 pm The existence of the Standard Model (SM) Higgs implies that a gravitational wave (GW) background is generated by the decay products of the Higgs, soon after the end of inflation. Theoretically, all Yukawa and SU(2)L gauge couplings of the SM are imprinted as features in the GW spectrum. However, in practice, the signal from the most strongly coupled species dominate, rendering inaccesible the information on the other species. This background could be used for inferring properties of particle physics, including beyond the SM, at energies way above the reach of LHC. To measure this background, however, new high frequency GW detection technology is required. Continue reading… Imprints of the Standard Model in the Sky? – Daniel G. Figueroa New Ideas for Dark Energy and Also for Dust Discrimination in B-mode Maps – Marc Kamionkowski Fri. November 14th, 2014 12:30 pm-1:30 pm Continue reading… New Ideas for Dark Energy and Also for Dust Discrimination in B-mode Maps – Marc Kamionkowski Intergalactic Magnetic Fields – Tanmay Vachaspati Tue. November 11th, 2014 11:30 am-12:30 pm I will describe theoretical motivation for the existence of parity violating (helical) intergalactic magnetic fields and recent and growing observational evidence for such fields. Continue reading… Intergalactic Magnetic Fields – Tanmay Vachaspati Soft Materials Approaches to Carbon Nanotubes: from Gels to Composites – Mohammed F. Islam Mon. November 10th, 2014 12:30 pm-1:30 pm Carbon nanotubes combine low density with exceptional mechanical, electrical and optical properties. Unfortunately, these nanoscale properties have not been retained in bulk structures. I will describe surface modification assisted self‐assembly of single wall carbon nanotube into macroscopic nanotube networks ‐ hydrogels and aerogels. The nanotube networks are ultra‐ lightweight, electrically conducting and thermally insulating. The shapes and sizes of these nanotube networks are readily tunable and is a tremendous strength of our fabrication method. The interesting properties and structure of these nanotube networks make them suitable for diverse applications. For example, we have used these networks as scaffolds to enhance elastic modulus of polymers by 40,000%. Continue reading… Soft Materials Approaches to Carbon Nanotubes: from Gels to Composites – Mohammed F. Islam 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. Continue reading… Neutrino Oscillations at Work – Jenny Thomas Peaks and Troughs in Large Scale Structure – Ravi K. Sheth Tue. November 4th, 2014 11:30 am-12:30 pm I will reiew recent and substantial progress in modeling the cosmic web. This progress, which results from merging two different and decades old literature streams, leads to a number of new and interesting insights about how the biased tracers we will observe in the next generation of large scale structure datasets can better constrain cosmological models. Continue reading… Peaks and Troughs in Large Scale Structure – Ravi K. Sheth 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. Continue reading… Physics and Language – Harsh Mathur Soft Magnetic Materials for Energy Applications in Extreme Environments – Matthew A. Willard Mon. October 27th, 2014 12:30 pm-1:30 pm A fundamental transformation of the transportation sector in the United States is underway. In parallel with advances in renewable energy resources for power generation, the rising use of electric and hybrid vehicles is reshaping the future of public transportation. Similar efforts are moving forward for more-electric ships, aircraft, and other military technologies. Due to their prevalence, magnetic materials play an important role in improving the efficiency and performance of devices in electric power generation, conditioning, and conversion. However, significant challenges exist for magnetic materials especially when used for transportation technologies, where enhanced reliability, power density, and overall energy capacity are increasingly important. Continue reading… Soft Magnetic Materials for Energy Applications in Extreme Environments – Matthew A. Willard High Precision Cosmology with BAO Surveys: BOSS and Future 21cm BAO Surveys – Hee-Jong Seo Fri. October 24th, 2014 12:30 pm-1:30 pm The large scale structure of matter and galaxies contains important information on the evolution of the Universe. Baryon acoustic oscillations (BAO), which is one of the most promising large scale features, can provide an excellent standard ruler that enables us to measure the cosmological distance scales, and therefore dark energy properties. I would like to first discuss the ongoing joint analysis of BOSS galaxy and lya BAO results and, second, future 21cm BAO surveys focused on the effect of foregrounds. Continue reading… High Precision Cosmology with BAO Surveys: BOSS and Future 21cm BAO Surveys – Hee-Jong Seo On Demand 2D Electron Gas at LaAlO3/SrTiO3 Interfaces – Cheng Cen Mon. October 20th, 2014 12:30 pm-1:30 pm The development of complex oxides over the past fifteen years has raised the prospect for new classes of electronic devices. In particular, it has been discovered that a high-mobility two-dimensional electron gas (2DEG) can be formed at the interface between two high-k insulators: LaAlO3 and SrTiO3. More interestingly, in samples with 3-unit-cell LaAlO3 (LAO) film grown on SrTiO3 (STO) substrate, a biased conducting atomic force microscope probe can locally and reversibly control the interfacial metal-insulator transition. This method is capable of patterning arbitrary conducting structures at LAO/STO interfaces with a spatial resolution of only a few nanometers. Based on such technique, Continue reading… On Demand 2D Electron Gas at LaAlO3/SrTiO3 Interfaces – Cheng Cen Sensing the ripples of time – Amar Vutha Fri. October 17th, 2014 12:30 pm-1:30 pm Almost a century since the dawn of general relativity, we have yet to obtain direct evidence of one of its key predictions: gravitational waves. In this lecture, I will point out how the precisely regular vibrations of atoms in optical atomic clocks can be used to detect the minuscule ripples in time due to gravitational waves. This approach requires portable atomic clocks with high sensitivity and reliable performance. I will describe one approach to realizing such clocks, and lay out the prospects for gravitational wave imaging and astronomy using arrays of satellite-borne clocks. These detectors would complement the efforts to detect gravitational waves using terrestrial (Michelson) interferometers, Continue reading… Sensing the ripples of time – Amar Vutha 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. Continue reading… Constraining supersymmetry using molecules – Amar Vutha Constraining supersymmetry using molecules – Amar Vutha Thu. October 16th, 2014 4:15 pm-5:15 pm Supersymmetry, and other theories that go beyond the Standard Model of particle physics, often predict the existence of new particles and interactions that act as sources of time-reversal violation. These, in turn, induce asymmetries in the charge distribution of electrons. In this colloquium, I will describe the stringent constraints on such new physics that were recently imposed by precise measurements with the thorium monoxide molecule (ACME Collaboration: Science, Jan 17, 2014). I will explain how polar molecules amplify the minuscule asymmetries of an electron’s charge distribution, how these molecules provide a useful suite of tools for experimenters, and the details of how we made the measurement. Continue reading… Constraining supersymmetry using molecules – Amar Vutha The Shape of the Electron, and Why It Matters – Amar Vutha Tue. October 14th, 2014 11:30 am-12:30 pm The universe, or at least the 5% of it that we understand, is described rather well by the Standard Model of particle physics. Yet even this non-dark sector of the universe conceals a great mystery: // where has all the anti-matter gone? // In this lecture, I will describe the problem and the best solution that we have for it. One of the crucial ingredients of that solution is the prediction of new sources of time-reversal violation. The most sensitive probe of such time-reversal violation is, oddly enough, to be found in small asymmetries in the shape of the electron’s charge distribution. Continue reading… The Shape of the Electron, and Why It Matters – Amar Vutha The shape of the electron, and why it matters – Amar Vutha Tue. October 14th, 2014 11:30 am-12:30 pm The universe, or at least the 5% of it that we understand, is described rather well by the Standard Model of particle physics. Yet even this non-dark sector of the universe conceals a great mystery: // where has all the anti-matter gone? // In this lecture, I will describe the problem and the best solution that we have for it. One of the crucial ingredients of that solution is the prediction of new sources of time-reversal violation. The most sensitive probe of such time-reversal violation is, oddly enough, to be found in small asymmetries in the shape of the electron’s charge distribution. Continue reading… The shape of the electron, and why it matters – Amar Vutha “How Big is the Proton Anyway?” – Amar Vutha Mon. October 13th, 2014 12:30 pm-1:30 pm The proton is a bound state of quarks and gluons, described by the low-energy limit of quantum chromodynamics. Recent measurements using muonic hydrogen have, however, called our understanding of proton physics into question. In this first lecture, I will describe the significant discrepancy that exists between the recent muonic hydrogen measurements and previous measurements on protons — this is the // proton radius puzzle //. In the absence of any feasible theoretical solutions, new experiments might provide the best clues. I shall describe some of the experiments that are attempting to shed light on this puzzle, including our ongoing efforts to measure the proton radius via the Lamb shift in hydrogen atoms. Continue reading… “How Big is the Proton Anyway?” – Amar Vutha How big is the proton anyway? – Amar Vutha Mon. October 13th, 2014 12:30 pm-1:30 pm The proton is a bound state of quarks and gluons, described by the low-energy limit of quantum chromodynamics. Recent measurements using muonic hydrogen have, however, called our understanding of proton physics into question. In this first lecture, I will describe the significant discrepancy that exists between the recent muonic hydrogen measurements and previous measurements on protons — this is the // proton radius puzzle //. In the absence of any feasible theoretical solutions, new experiments might provide the best clues. I shall describe some of the experiments that are attempting to shed light on this puzzle, including our ongoing efforts to measure the proton radius via the Lamb shift in hydrogen atoms. Continue reading… How big is the proton anyway? – Amar Vutha Precision Cosmology with Galaxy Surveys: Understanding Intrinsic Alignments and Redshift-space Distortions – Jonathan A. Blazek Fri. October 10th, 2014 12:30 pm-1:30 pm Galaxy imaging and redshift surveys, designed to measure gravitational lensing and galaxy clustering, remain the most powerful probes of large-scale structure. Such surveys constitute a significant fraction of current and next-generation projects in the cosmology community (e.g. DES, HSC, LSST, eBOSS, DESI, EUCLID, WFIRST). The statistical power of these experiments requires significantly improved understanding of astrophysical and observational effects. In this talk, I will focus on two important astrophysical processes which contribute systematic uncertainty but also contain a potential wealth of information. First, correlations in the intrinsic shapes and orientations of galaxies, termed “intrinsic alignments” (IA), are an important systematic in weak lensing. Continue reading… Precision Cosmology with Galaxy Surveys: Understanding Intrinsic Alignments and Redshift-space Distortions – Jonathan A. Blazek 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, strong optical absorption and their gap can be fine tuned with chemical substitutions. Continue reading… Halide perovskites: their unusual combination of properties and its impact on solar cell applications – Walter Lambrecht Spin-charge Conversion in Interfacial Electron Liquids – Giovanni Vignale Mon. October 6th, 2014 12:30 pm-1:30 pm Semiconductor quantum wells, inter-metallic interfaces, layered oxides, and monolayer materials are all promising platforms for the observation of spincharge conversion due to strong spin-orbit interaction in the quasi two dimensional electron liquid they host. In this talk I focus on two closely related effects that can occur in these materials, namely the conversion of charge current to spin current (spin Hall effect) and the generation of spin polarization from an electric current (Edelstein effect). Together with their inverses (in the sense of Onsager reciprocity relations), these effects constitute a useful set of tools for spintronic applications. The theoretical challenge is to provide a unified treatment of the different mechanisms at work, Continue reading… Spin-charge Conversion in Interfacial Electron Liquids – Giovanni Vignale 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. Continue reading… The Standard Model and Beyond with Ultracold Neutrons – Leah Broussard 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. Continue reading… Quantum Mechanics Without Measurements – Robert Griffiths 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. Continue reading… The black hole information paradox and its resolution in string theory – Samir Mathur 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, Continue reading… Building Nuclear Bombs in Your Basement: the technology of nuclear proliferation – R. Scott Kemp Healthy Theories Beyond Horndeski – Jerome Gleyzes Wed. September 3rd, 2014 11:30 am-12:30 pm In search for a candidate that could explain the current acceleration of the Universe, a lot of attention has been given recently to Galileon theories, or in their generalized form, Horndeski theories. They are interesting as they represent the most general scalar tensor theories that do not lead to equations of motion containing more than two derivatives. This restriction is generally thought to be of great importance, as generically, higher order derivatives lead to ghost instabilities. I will present a new class of scalar tensor theories that are broader than Horndeski and, as such, do bring higher order derivatives. However, Continue reading… Healthy Theories Beyond Horndeski – Jerome Gleyzes Interacting Spin-2 Fields – Johannes Noller Tue. September 2nd, 2014 11:30 am-12:30 pm In this talk I will discuss some recent progress in our understanding of the spin-2 sector, focussing on theories with two or more dynamical such fields. In particular I will highlight the existence of several dualities in such models (generalisations of `Galileon dualities’), their decoupling limit phenomenology as well as the form of their interactions with other matter fields. Continue reading… Interacting Spin-2 Fields – Johannes Noller 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. Continue reading… Getting research news out: connecting with the press and DIY communication – Kate McAlpine Recent Progress in Large-Scale Structure – Roman Scoccimarro Fri. May 9th, 2014 11:00 am-12:00 pm I will discuss recent progress in the understanding of how to model galaxy clustering. While recent analyses have focussed on the baryon acoustic oscillations as a probe of cosmology, galaxy redshift surveys contain a lot more information than the acoustic scale. In extracting this additional information three main issues need to be well understood: nonlinear evolution of matter fluctuations, galaxy bias and redshift-space distortions. I will present recent progress in modeling these three effects that pave the way to constraining cosmology and galaxy formation with increased precision. Continue reading… Recent Progress in Large-Scale Structure – Roman Scoccimarro Atom Interferometry Fundamentals and its Applications in Space Science – Babak Saif Tue. May 6th, 2014 11:30 am-12:30 pm Continue reading… Atom Interferometry Fundamentals and its Applications in Space Science – Babak Saif Shape of the Universe – Daniel Müller Tue. April 29th, 2014 11:30 am-12:30 pm The most recent observations indicate that the Universe is isotropic, with a small spatial curvature, which can be either positive, negative or zero. As is well known, Einstein’s theory of gravitation restricts the spatially isotropic sections of space time to be locally S^3, H^3 or E^3, respectively. Thus, the topology of the Universe is only partly determined. On the other hand there are a few effects which occur for non trivial topology. In this talk, we will give a brief discussion of some of these, in particular of the Casimir effect which should have been important in the primordial stages of the Universe. Continue reading… Shape of the Universe – Daniel Müller 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. Continue reading… Our MRI Startup Grows Up: QED and HealthCare in 2014 – Hiroyuki Fujita Testing Gravity via Lunar Laser Ranging – Tom Murphy Tue. April 22nd, 2014 11:30 am-12:30 pm Forty years ago, Apollo astronauts placed the first of several retroreflector arrays on the moon. Laser range measurements between the earth and the moon have provided some of our best tests to date of general relativity and gravitational phenomenology–including the equivalence principle, the time-rate-of-change of the gravitational constant, the inverse square law, and gravitomagnetism. A new effort called APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) is now collecting measurements at the unprecidented precision of one millimeter, which will produce order-of-magnitude improvements in a variety of gravitational tests, as well as reveal more detail about the interior structure of the moon. Continue reading… Testing Gravity via Lunar Laser Ranging – Tom Murphy 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, Continue reading… Chasing Inflation – John Ruhl 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. Continue reading… Super-Resolution Microscopies at the Frontiers of Cell Biology (co-sponsored by the Institute for the Science of Origins) – Bill Dougherty WIMP physics with direct detection – Annika H. G. Peter Tue. April 8th, 2014 11:30 am-12:30 pm One of the best-motivated classes of dark-matter candidate is the Weakly-Interacting Massive Particle (WIMP). In this talk, I will discuss WIMPs in the context of direct-detection experiments. First, I will discuss a new signal for WIMP dark matter: gravitational focusing in direct-detection experiments. This effect leads to an energy-dependent phase-shift in the peak direct-detection event rate throughout the year. I will discuss this in light of current putative annual-modulation claims. Second, I will discuss what we can learn about WIMPs in the “early-discovery” days once WIMPs are conclusively found in direct-detection experiments. I will show that what we can learn about WIMPs depends sensitively on the ensemble of experiments that are running at the time of discovery. Continue reading… WIMP physics with direct detection – Annika H. G. Peter Results from the LUX dark matter search, and prospects for the future – Tom Shutt Thu. April 3rd, 2014 4:15 pm-5:15 pm Continue reading… Results from the LUX dark matter search, and prospects for the future – Tom Shutt Probing Dark Energy Using Growth of Structure: The Role of Simulations – Hao-Yi Wu Tue. April 1st, 2014 11:30 am-12:30 pm The growth of cosmic structure provides a unique approach for measuring the dynamic evolution of dark energy and distinguishing different models of gravity. In this talk, I will focus on two of the most important methods for measuring the growth of structure: galaxy cluster counts and the redshift-space distortions of galaxy clustering. I will discuss the systematic uncertainties involved in both methods, and how I use numerical simulations to help reducing these systematics and improve our theoretical predictions. Continue reading… Probing Dark Energy Using Growth of Structure: The Role of Simulations – Hao-Yi Wu 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, Continue reading… Arrested Development (of Emulsions) – Tim Atherton 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, Continue reading… Nanoscale thermal transport – Alexis Abramson Science with CMB Spectral Distortions: a New Window to Early-Universe Physics – Jens Chluba Tue. March 18th, 2014 11:30 am-12:30 pm Since COBE/FIRAS we know that the CMB spectrum is extremely close to a perfect blackbody. There are, however, a number of processes in the early Universe that should create spectral distortions at a level that is within reach of present day technology. I will give an overview of recent theoretical and experimental developments, explaining why future measurements of the CMB spectrum will open up an unexplored window to early-universe and particle physics, with possible non-standard surprises but also guaranteed signals awaiting us. Continue reading… Science with CMB Spectral Distortions: a New Window to Early-Universe Physics – Jens Chluba 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. Continue reading… Curvature and defects in liquid crystals and other soft materials: Differential geometry isn’t just for cosmology any more! – Jonathan Selinger The Marvelous Success of the Standard Model of Cosmology – Lloyd Knox Wed. February 26th, 2014 12:30 pm-1:30 pm The standard model of cosmology has been remarkably successful in its predictions for current data given earlier data. One can react with sadness for the lack of evidence for new physics, chase marginal anomalies, or marvel at the success and soldier on toward better measurements knowing new physics may be just around the corner. In this talk I will reveal some of the inner workings of this success in order to communicate why I find it marvelous. For example, for the predictions to agree with cosmic microwave background (CMB) data we need, at very high statistical significance, a cosmic neutrino background, Continue reading… The Marvelous Success of the Standard Model of Cosmology – Lloyd Knox 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? Continue reading… The Hunt for the Missing Components of the Universe: Dark Matter, Dark Energy . . . . and Women in Physics. – Evalyn Gates 21cm Cosmology – Ue-Li Pen Tue. February 18th, 2014 11:30 am-12:30 pm I present recent developments in a new window to map the large scale structure of the universe through intensity mapping using the collective unresolved emission of cosmic hydrogen 21cm emission. Initial maps have been made with various existing telescopes, and an ambitious survey, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is under construction. Future potential science targets include precision measurements of dark energy, neutrino masses, and possibly gravitational waves. Continue reading… 21cm Cosmology – Ue-Li Pen Cosmology and Systematics of Multi-wavelength Galaxy Cluster Observables – Tomasz Biesiadzinski Tue. February 11th, 2014 11:30 am-12:30 pm The current concordance lCDM cosmological model describes a universe where cold dark matter seeds structure formation and a cosmological constant drives its accelerated expansion. Precise measurements of various astronomical observables allow us to test this model and any deviations, if found, may lead to an improved cosmological theory. Ongoing and planned large scale surveys of the skies have the power to study the lCDM model. However the data sets they generate will be dominated by complex systematic uncertainties. One probe of cosmological parameters, the evolution of clusters of galaxies, has the power to differentiate simple models of dark energy, like the cosmological constant, Continue reading… Cosmology and Systematics of Multi-wavelength Galaxy Cluster Observables – Tomasz Biesiadzinski Quantum-Limited Superconducting Detectors and Amplifiers for Cosmology – Philip Mauskopf Fri. February 7th, 2014 12:30 pm-1:30 pm Continue reading… Quantum-Limited Superconducting Detectors and Amplifiers for Cosmology – Philip Mauskopf 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. Continue reading… Mercury’s interior: New views from MESSENGER – Steven Hauck 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 PhysiologyDr. Michael Weiss (Biochemistry)on the prize for ChemistryDr. Glenn Starkman (Physics) on the prize for Physics Continue reading… The 2013 Science Nobel Prizes – What were they given for? – Martin Snider, Michael Weiss, Glenn Starkman 21-cm Intensity Mapping – Jeffrey Peterson Tue. January 28th, 2014 11:30 am-12:30 pm Continue reading… 21-cm Intensity Mapping – Jeffrey Peterson 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. Continue reading… Next Steps in Neutrino Physics – Geralyn Zeller 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. Continue reading… The Physics of Climate Change – Michael Mann 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, Continue reading… In proximity to novel physics: Topological Insulators coupled to Superconductors – Nadya Mason Supersymmetry, Non-thermal Dark Matter and Precision Cosmology Tue. December 3rd, 2013 11:30 am-12:30 pm Within the Minimal Supersymmetric Standard Model (MSSM), LHC bounds suggest that scalar superpartner masses are far above the electroweak scale. Given a high superpartner mass, nonthermal dark matter is a viable alternative to WIMP dark matter generated via freezeout. In the presence of moduli fields nonthermal dark matter production is associated with a long matter dominated phase, modifying the spectral index and primordial tensor amplitude relative to those in a thermalized primordial universe. Nonthermal dark matter can have a higher self-interaction cross-section than its thermal counterpart, enhancing astrophysical bounds on its annihilation signals. I will review recent progress in this program, Continue reading… Supersymmetry, Non-thermal Dark Matter and Precision Cosmology Cosmic Bandits: Exploration vs. Exploitation in Cosmological Surveys – Ely Kovetz Tue. November 26th, 2013 11:30 am-12:30 pm Various cosmological observations consist of prolonged integrations over small patches of sky. These include searches for B-modes in the CMB, the power spectrum of 21-cm fluctuations during the epoch of reionization and deep-field imaging by telescopes such as HST/JWST, among others. However, since these measurements are hindered by spatially-varying foreground noise, the observational sensitivity can be improved considerably by finding the region of sky cleanest of foregrounds. The best strategy thus involves a tradeoff between exploration (to find lower-foreground patches) and exploitation (through prolonged integration). But how to balance this tradeoff efficiently? This problem is akin to the multi-armed bandit (MAB) problem in probability theory, Continue reading… Cosmic Bandits: Exploration vs. Exploitation in Cosmological Surveys – Ely Kovetz 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. Continue reading… Fukushima: Implications for the Understanding of Severe Accidents and the Future of Nuclear Energy – M.V. Ramana Turning trajectories in multi-field inflation – Krzysztof Turzyński Tue. November 19th, 2013 11:30 am-12:30 pm The latest results from the PLANCK collaboration, consistent with the simplest single-field models of slow-roll inflation and with no trace of non-Gaussianity, have extinguished many hopes of seeing specific aspects of New Physics directly in the sky. One may then wonder whether the landscape of allowed inflationary models has been practically reduced to single-field effective theories. I shall argue that the answer is negative and present several inflationary models in which the turn-induced interactions between two scalar fields affect the normalization/running of the power spectrum of curvature perturbations, or smooth out its features (e.g. via particle production), actually driving the power spectrum towards phenomenologically acceptable characteristics. Continue reading… Turning trajectories in multi-field inflation – Krzysztof Turzyński Lorentz violation in gravity: why, how and where – Diego Blas Mon. November 18th, 2013 3:00 pm-4:00 pm Recent approaches to quantum gravity question the role of Lorentz invariance as a fundamental symmetry of Nature. This has implications for most of the observables in gravitational physics, also at low-energies. In this talk I will describe recent bounds on deviations from Lorentz invariance in gravity coming from binary pulsar observations and cosmological data. Continue reading… Lorentz violation in gravity: why, how and where – Diego Blas 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. Continue reading… Magnetism Without Magnetic Atoms: The Physics of the Vacancy Center in Graphene – Sashi Satpathy Non-local quantum effects in cosmology – John Donoghue Tue. November 12th, 2013 11:30 am-12:30 pm In general relativity, there are non-local quantum effects that come from the propagation of light particles including gravitons. I will review the effective field theory treatment which allows one to identify the reliable parts of the quantum loops. In cosmology, there are then non-local corrections to the FLRW equations. I will present some of the formalism for this and give some exploration of results. Continue reading… Non-local quantum effects in cosmology – John Donoghue New Possibilities in Transition-metal oxide Heterostructures – Wei-Cheng Lee Fri. November 8th, 2013 12:30 pm-1:30 pm Heterojunction, the interface between two dissimilar crystalline materials, has been one of ideal platforms for the two-dimensional electronic systems (2DES). Examples include the quantum Hall effect which was first observed in the semiconductor heterostructures. Recently, a heterostructure made from two transition metal oxides LaTiO3 and SrTiO3 has opened a new door for us to engineer the physical properties of transition metal oxides. In particular, since many of the transition metal oxides are strongly correlated materials, new types of 2DES with strong correlation could emerge from these new oxide interfaces. In this talk, I will first introduce the experimental and theoretical developments in this new field. Continue reading… New Possibilities in Transition-metal oxide Heterostructures – Wei-Cheng Lee 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. Continue reading… To Superconduct or Not to Superconduct; That is the Question – Michelson Postdoctoral Prizewinner Wei-Cheng Lee To Superconduct or Not to Superconduct; That is the Question? – Wei-Cheng Lee Thu. November 7th, 2013 4:15 pm-5:15 pm Superconductor, a material losing resistivity below a critical temperature Tc, remains one of the grand challenges in physics. This field began in 1911 with the discovery of superconductivity in mercury at 4.2 K. After the birth of a complete microscopic theory of superconductivity proposed by Bardeen, Cooper, and Schrieffer in 1957, known as BCS theory, it was believed that no materials could have Tc higher than 30 K. The discovery of new classes of superconductors, cuprates in 1986 (which shatter the 30 K barrier) and iron pnictides in 2008, launched an international wave of research to find new materials with higher Tc. Continue reading… To Superconduct or Not to Superconduct; That is the Question? – Wei-Cheng Lee Novel Collective modes in Unconventional Superconductors – Wei-Cheng Lee Tue. November 5th, 2013 12:30 pm-1:30 pm Unconventional superconductors are materials whose pairing mechanism is not due to the electron-phonon interaction as proposed by BCS theory. Up to date, known unconventional superconductors all exhibit symmetry-broken phases other than superconductivity in their phase diagrams, and it is widely-believed that the fluctuations associated with these symmetry-broken phases hold the key to the pairing mechanism of unconventional superconductors. In this talk, I will summarize our work in studying the collective excitations in cuprates and iron pnictides observed in inelastic neutron scattering and optical measurements. Their implications on the pairing mechanism will be discussed. Continue reading… Novel Collective modes in Unconventional Superconductors – Wei-Cheng Lee Orbital Aspect of Iron-based Superconductivity – Wei-Cheng Lee Mon. November 4th, 2013 12:30 pm-1:30 pm In this talk, I will focus on the new classes of high-temperature superconductors, iron pnictides. While the magnetic interactions are certainly important in these materials, there have been significant evidences suggesting that the orbital degrees of freedom could play an important role as well. From both theoretical and experimental aspects, I will argue that the orbital degrees of freedom do play a game-changing role in physical properties of iron based superconductors. I will show that at the single particle level, the orbital order in the quasi-1D dxz and dyz bands induces a distortion of the Fermi surface, which could result in the structural phase transition. Continue reading… Orbital Aspect of Iron-based Superconductivity – Wei-Cheng Lee 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. Continue reading… Graphene at the Boundaries – Paul McEuen Cosmology from conformal symmetry – Austin Joyce Tue. October 29th, 2013 11:30 am-12:30 pm We will explore the role that conformal symmetries may play in cosmology. First, we will discuss the symmetries underlying the statistics of the primordial perturbations which seeded the temperature anisotropies of the Cosmic Microwave Background. I will show how symmetry considerations lead us to three broad classes of theories to explain these perturbations: single-field inflation, multi-field inflation, and the conformal mechanism. We will discuss the symmetries in each case and derive their model-independent consequences. Finally, we will examine the possibility of violating the null energy condition with a well-behaved quantum field theory. Continue reading… Cosmology from conformal symmetry – Austin Joyce 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. Continue reading… The Cosmic Gravitational Wave Background – Tom Giblin 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. Continue reading… Dark Materials: the Topology of Insulators – Harsh Mathur Goldstone bosons with spontaneously broken Lorentz symmetry – Riccardo Penco Tue. October 15th, 2013 11:30 am-12:30 pm In this talk, I will discuss some general properties of effective theories of Goldstone bosons in which Lorentz symmetry is spontaneously broken. I will first introduce an extension of Goldstone theorem to systems with a finite density of charge. This very general setting is potentially applicable to contexts as diverse as early universe cosmology and QCD at finite density. Additionally, I will show how certain effective theories of Goldstones with broken Lorentz symmetry admit UV completions that do not restore any broken symmetry. Continue reading… Goldstone bosons with spontaneously broken Lorentz symmetry – Riccardo Penco 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, Continue reading… Isostatic Lattice: From Jamming to Topological Surface Phonons – Tom Lubensky Slavnov-Taylor Identities for Primordial Perturbations – Lasha Berezhiani Tue. October 8th, 2013 11:30 am-12:30 pm I will show that all consistency relations for the primordial perturbations derive from a single, master identity, which follows from the Slavnov-Taylor identity for spatial diffeomorphisms. This master identity is valid at any value of momenta and therefore goes beyond the soft limit. This approach underscores the role of spatial diffeomorphism invariance at the root of cosmological consistency relations. It also offers new insights on the necessary conditions for their validity: a physical contribution to the vertex functional must satisfy certain analyticity properties in the soft limit in order for the consistency relations to hold. For standard inflationary models, this is equivalent to requiring that mode functions have constant growing-mode solutions. Continue reading… Slavnov-Taylor Identities for Primordial Perturbations – Lasha Berezhiani 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, Continue reading… Modeling and simulating cellular processes in the brain: a mathematical challenge – Daniela Calvetti Symmetry Breaking and Galileons – Garrett Goon Wed. October 2nd, 2013 11:30 am-12:30 pm Galileons, and related theories, have deep connections to spontaneous symmetry breaking. After reviewing the origins of Galileon theories, I motivate their interpretation as Goldstone Bosons and illustrate some of their special technical properties before proceeding to discuss applications and future directions. Continue reading… Symmetry Breaking and Galileons – Garrett Goon 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. Continue reading… Michelson and Morley –the men, the experiment, and the 1987 Centennial Celebration – Various + P. Taylor CMB Lensing: reconstruction from polarisation & implications for cosmology from cross correlation with galaxies – Ruth Pearson Tue. September 24th, 2013 11:30 am-12:30 pm CMB Lensing is a probe of the matter distribution between the surface of last scattering and today, which has been measured using CMB temperature data. Signal to noise for lensing reconstruction from CMB polarisation data is expected to be much better, since B modes on small scales should vanish in the absence of lensing. An effect of having data from an incomplete sky is leakage of E mode power in to B mode power. Upcoming data analysis from ground based CMB polarisation instruments must account for this effect. In the first part of my talk I will show results for CMB polarisation lensing reconstruction from small patches of sky, Continue reading… CMB Lensing: reconstruction from polarisation & implications for cosmology from cross correlation with galaxies – Ruth Pearson 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. Continue reading… Green commercial buildings: are they saving energy or are they just making us feel good? – John Scofield 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. Continue reading… To wet or not to wet? That is the Question – Milton Cole Making the connection between galaxy voids, dark matter underdensities and theory – Paul Sutter Tue. September 10th, 2013 11:30 am-12:30 pm TBA Continue reading… Making the connection between galaxy voids, dark matter underdensities and theory – Paul Sutter 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. Continue reading… Light or Dark? Mass and Gravity in the Universe – Stacy McGaugh “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. Continue reading… “Look to the Stars” – an episode starring Case’s first Physics Professor – Albert A. Michelson Ordered self-assembly of molecules on gold substrates, for activated organic monolayers – Prof. Emmanuelle Lacaze Wed. July 17th, 2013 12:30 pm-1:30 pm Photochromic molecules are characterized by a functional group whose configuration is modified by absorption of light, in a reversible manner. They could be at the basis of new electronic displays which would be activated by light irradiation. For the formation of ultra-thin electronic displays, researchers now try to adsorb them on metallic substrates. Two main questions are thus asked : Firstly, is it possible to self-assemble this type of molecule on a substrate. Second, when self-assembled in monolayer, do the molecules remain active under irradiation, and most importantly, can they be locally switched under STM tip Ordered self-assemblies have been successfully obtained with azo-benzene based photochromes, Continue reading… Ordered self-assembly of molecules on gold substrates, for activated organic monolayers – Prof. Emmanuelle Lacaze Topological transition of graphene from quantum Hall metal to quantum Hall insulator – Prof. XiangRong Wang Fri. May 17th, 2013 12:30 pm-1:30 pm In this talk, I will first review the basic electronic properties of graphene. In particular, I will explain why the recently observed insulating phase of graphene at charge neutrality point in high magnetic field quantum Hall (QH) experiments is a big surprising. Then I will present a simple single-particle theory for this intriguing finding. We show that the magnetic field driven Peierls-type lattice distortion (due to the Landau level degeneracy) and random bond fluctuations compete with each other, resulting in a transition from a QH-metal state at relative low field to a QH-insulator state at high enough field at the charge neutrality point. Continue reading… Topological transition of graphene from quantum Hall metal to quantum Hall insulator – Prof. XiangRong Wang The Universe in a New Light: the First Cosmological Results from the Planck Mission – Bill Jones Tue. April 30th, 2013 2:30 pm-3:30 pm The precision and accuracy of the recently released Planck data are without precedent; the data from a single experiment provide all-sky images at wavelengths never before explored, covering more than three decades in angular scale with a signal dynamic range exceeding a factor of a million. These data open new avenues of research in fields ranging from Galactic astrophysics to cosmology. Our present Universe has shown herself to be both simple and elegant, and although her origins remain enshrouded in mystery, it appears that her past may have been more complex. While the Planck data have begun to inform us about the nature of cosmo-genesis, Continue reading… The Universe in a New Light: the First Cosmological Results from the Planck Mission – Bill Jones Detecting Modified Gravity in the Stars – Jeremy Sakstein Mon. April 29th, 2013 10:30 am-11:30 am Screened scalar-tensor gravity such as chameleon and symmetron theories allow order one deviations from General Relativity on large scales whilst satisfying all local solar-system constraints. A lot of recent work has therefore focused on searching for observational signatures of these models and constraining them. If these models are to be viable then our own solar system is necessarily screened, however, this may not be the case for stars in dwarf galaxies, which can exhibit novel and unique phenomena. These new effects can be exploited to produce constraints that are far more competitive than laboratory and cosmological tests and in this talk, Continue reading… Detecting Modified Gravity in the Stars – Jeremy Sakstein Quantum Fluids of Light – David Snoke Mon. April 29th, 2013 12:30 pm-1:30 pm In the past few years a new class of solid state optical systems has been developed in which photons have an effective mass and a repulsive interaction between each other. These renormalized photons are known as “polaritons”. One way of looking at this type of system is as an optical medium with world-record nonlinearity, leading to new possibilities for modulating light. Another way of looking at this type of system is as an analogue of a gas of atoms, which can undergo Bose-Einstein condensation and can become superfluid, allowing us to study superfluidity in a new way. I will review the basic experimental methods and recent results of polariton superfluids. Continue reading… Quantum Fluids of Light – David Snoke Semiconductor nanowires : from LEDs to solar cells – Silvija Gradecak Mon. April 22nd, 2013 12:30 pm-1:30 pm Semiconductor nanowires are quasi-one-dimensional single-crystals that have emerged as promising materials for the development of photonic and electronic devices with enhanced performance. Nanowires offer solutions to some of the current challenges in science and engineering, but realization of their full potential will be ultimately dictated by the ability to control their structure, composition, and size with high accuracy. In this talk, I will discuss our recent results on the controlled growth, doping, and applications of III-V nanowires, as well as advanced electron microscopy techniques for direct correlation of structural and physical properties with high spatial resolution. We have developed a simple, Continue reading… Semiconductor nanowires : from LEDs to solar cells – Silvija Gradecak Senior Project Symposium Sat. April 20th, 2013 11:30 am-12:30 pm Continue reading… Senior Project Symposium 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. Continue reading… Some Experiences Gained in Starting and Growing Optical Companies – James C. Wyant In search for hints of resonance in the CMB power spectrum – Daan Meerburg Tue. April 16th, 2013 11:30 am-12:30 pm We investigate possible resonance effects in the primordial power spectrum using the latest CMB data. These effects are predicted by a wide variety of models and come in two flavors, one where the oscillations are log spaced and one where the oscillations are linearly spaced. We treat the oscillations as perturbations on top of the scale invariant power spectrum. This allows us to significantly improve the search for resonance because it allows us to precompute the transfer functions. We show that the largest error from this simplification comes from the variance in the measurement to the distance of last scattering. Continue reading… In search for hints of resonance in the CMB power spectrum – Daan Meerburg Mapping spin-orbit effects in semiconductors – Vanessa Sih Mon. April 15th, 2013 12:30 pm-1:30 pm Spin-orbit coupling is a consequence of relativity but can be observed and used at the device scale to electrically initialize and manipulate electron spin polarization. Understanding how to exploit spin-orbit effects in non-magnetic semiconductors may enable the development of new devices with enhanced functionality and performance, such as spin-based devices that combine logic and storage and fast optical switches for information processing. In this talk, I will describe time- and spatially-resolved measurements of electron spin transport that enable sensitive measurements of the spin-orbit field and its dependence on applied electric fields and mechanical strain. These spin splittings also provide a mechanism for the electrical generation of spin polarization. Continue reading… Mapping spin-orbit effects in semiconductors – Vanessa Sih 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. Continue reading… Origin of rigidity in granular solids – Bulbul Chakraborty Black Hole Space-Times from S Matrices – Ira Rothstein Tue. April 9th, 2013 11:30 am-12:30 pm In this talk I will show how to generate classical space-times directly from S matrices. The method makes no use of Einsteins’ equations nor, for that matter, any space-time action at all. This approach also allows us to make direct contact between the classical solutions of Yang-Mills theory and those of gravity through the squaring relation between the Yang-Mills and gravitational tree level scattering amplitudes. In this way one may construct classical space-times directly from Yang-Mills theory. – Continue reading… Black Hole Space-Times from S Matrices – Ira Rothstein Short-range order in nematic liquid crystals formed by reduced symmetry molecules – Sam Sprunt Mon. April 8th, 2013 12:30 pm-1:30 pm Small molecules constructed from familiar chemical components, but with an unconventional (reduced symmetry) molecular shape, hold promise for developing nematic liquid crystals with macroscopic biaxiality or even polarity. These properties, realized over practical temperature ranges using thermotropic compounds, could open new avenues in technologies including optical displays, mechanical sensors, and low-cost personal power generation. I will report on recent studies of short-range order – a guidance, if not a direct precursor, to rational development of biaxial/polar nematics – in three types of reduced symmetry thermotropic materials: bent-core (V-shaped) liquid crystal compounds and rod-like molecules containing either lateral branches (Y-shaped) or bridges (H-shaped). Continue reading… Short-range order in nematic liquid crystals formed by reduced symmetry molecules – Sam Sprunt 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. Continue reading… The discovery of a new particle. Is it the Higgs? – Daniela Bortoletto Testing gravity with pulsars, black holes and the microwave background – Lam Hui Tue. April 2nd, 2013 11:30 am-12:30 pm We will discuss 3 topics: 1. a way to detect gravitational waves using binaries; 2. a way to test general relativity using black holes; 3. a way to connect superhorizon fluctuations with the observed statistical asymmetry of the universe. Continue reading… Testing gravity with pulsars, black holes and the microwave background – Lam Hui Hybrid Quantum Devices with Single Spins in Diamond – Gurudev Dutt Mon. April 1st, 2013 12:30 pm-1:30 pm Single spins associated with defects in diamond have emerged as a promising and versatile experimental system. They can be used as qubits in optically connected quantum networks, as sensors for magnetic imaging with sub-micron resolution, as readout heads for detecting and engineering quantum states of nano-mechanical oscillators, and even as probes in biological systems. I will discuss some of the key experimental progress and future prospects along these paths. Continue reading… Hybrid Quantum Devices with Single Spins in Diamond – Gurudev Dutt 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. Continue reading… Random laser, bio-inspired laser, and time-reversed laser – Hui Cao Neutrinoless double beta decay results from EXO-200 – Carter Hall Tue. March 26th, 2013 11:30 am-12:30 pm Neutrinoless double beta decay has never been definitively observed, although for the last ten years one group has claimed to see a 6-sigma positive effect in 76Ge. Recently the EXO-200 experiment produced the first independent check on this claim using 136Xe. This talk will report on the double beta decay results from EXO-200 and other experiments, along with prospects for future progress in this field. Continue reading… Neutrinoless double beta decay results from EXO-200 – Carter Hall Point defect studies in ZnO: oxygen vacancy and p-type doping – Walter Lambrecht Mon. March 25th, 2013 12:30 pm-1:30 pm In the first part of the talk, I will tell you about the controversy about the position of the defect levels for the oxygen vacancy in ZnO and how we tried to resolve it. In the second part, I will discuss the case of nitrogen in ZnO. I will discuss why nitrogen on an oxygen site forms a deep rather than shallow acceptor level. However, it is known that there exists a shallow level related to nitrogen doping. The question is then what defect complex is responsible for this shallow level? I will try to convince you that a N2 molecule located on a Zn-site has all the expected behavior of a shallow acceptor. Continue reading… Point defect studies in ZnO: oxygen vacancy and p-type doping – Walter Lambrecht 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, Continue reading… Hamiltonian Theory of Fractional Chern Bands – R. Shankar Semiconductor nanocrystals for room-temperature coherent electronics: A flexible platform for manipulating spin coherence – Jesse Berezovsky Mon. March 4th, 2013 12:30 pm-1:30 pm One route towards future electronics is to exploit interactions between coherent electron spin states and photons in semiconductor structures. This will require an understanding of the coherent evolution of spin states, the eventual decoherence of these states, and how these states interact with light, all in a scalable room-temperature system. In this seminar, I will present our work on spins in semiconductor nanocrystal quantum dots (NCQDs). This system provides a platform to study room-temperature coherent spin states and their interactions with light. In an NCQD, a spin optically initialized into a superposition of eigenstates remains coherent for approximately one nanosecond at room temperature. Continue reading… Semiconductor nanocrystals for room-temperature coherent electronics: A flexible platform for manipulating spin coherence – Jesse Berezovsky 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. Continue reading… Molecular interactions: linking physics and biology – Yi-Kuo Yu CMB Non-Gaussianity from Recombination and Fingerprints of Dark Matter – Cora Dvorkin Tue. February 26th, 2013 11:30 am-12:30 pm In this talk, I show that dark matter annihilation around the time of recombination can lead to growing ionization perturbations, that track the linear collapse of matter overdensities. This amplifies small scale cosmological perturbations to the free electron density by a significant amount compared to the usual acoustic oscillations. Electron density perturbations distort the CMB, inducing secondary non-gaussianity, offering a means of detection by Planck and other experiments. I will present a novel analytic calculation of CMB non-gaussianity from recombination, providing a clear identification of the relevant physical processes. I will show that, even though electron perturbations can be markedly boosted compared with the standard model prediction, Continue reading… CMB Non-Gaussianity from Recombination and Fingerprints of Dark Matter – Cora Dvorkin Shedding some light on liquid crystalline organic semiconductors – Brett Ellman Mon. February 25th, 2013 12:30 pm-1:30 pm We live in a world whose technology is ruled by a small set of inorganic semiconductors, notably silicon. Research on organic semiconductors (OSCs), molecular materials based on organic compounds, seeks to supplement the reigning paradigm rather than to supplant it. In particular, OSCs may improve photovoltaics, LEDs, sensors, and flexible, cheap electronics. In this talk, I will describe recent work at Kent State on liquid crystalline (LC) semiconductors, a subclass of OSCs that offer distinct advantages and disadvantages relative to more common crystalline or polymeric organics. After a (very) short introduction to the physics of OSCs and LCs, I will discuss how the ability to align the molecules in LC OSCs over macroscopic distances can (profoundly) improve transport characteristics. Continue reading… Shedding some light on liquid crystalline organic semiconductors – Brett Ellman 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. Continue reading… Many Worlds, the Born Rule, and Self-Locating Uncertainty – Sean Carroll Nanostructures in Motion: Probing Surface Science and Fracture Mechanics at Molecular Level – Zenghui Wang Mon. February 18th, 2013 12:30 pm-1:30 pm Nanomaterials, since their debut, have greatly advanced human knowledge from many aspects. For example, carbon-based nanomaterials, such as carbon nanotube and graphene, have been the subjects of intensive study over the last two decades and greatly improved our understanding of phenomena happening at the nanoscale. On the other hand, microelectromechanical systems, MEMS, research has thrived over the last few decades in the engineering field and brought along many new applications. In this talk, I will illustrate that, by combining nanomaterials with MEMS technology, even more new opportunities and new sciences can be unveiled. I will mostly focus two systems: 1. Continue reading… Nanostructures in Motion: Probing Surface Science and Fracture Mechanics at Molecular Level – Zenghui Wang 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. Continue reading… Electrostatic charging of flowing granular materials – Dan Lacks Self-Assembly and Packing of Polyhedra into Complex Structures – Michael Engel Mon. February 11th, 2013 12:30 pm-1:30 pm Isolating the role of building block shape for self-assembly and packing provides insight into the ordering of molecules and the crystallization of colloids, nanoparticles, proteins, and viruses. We investigated a large group of polyhedra whose phase behavior arises solely from their anisotropic shape. At intermediate packing density, our results demonstrate a remarkably high propensity for thermodynamic self-assembly and structural diversity. We show that from simple measures of particle shape and local order in the fluid, the assembly of a given shape into a liquid crystal, plastic crystal, or crystal can be predicted. Towards higher density, packing considerations dominate. Good packings can often be distinct from what is observed to assemble from the disordered state. Continue reading… Self-Assembly and Packing of Polyhedra into Complex Structures – Michael Engel 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. Continue reading… The 2012 Science Nobel Prizes – What were they given for? – George Dubyak (Physiology and Biophysics), Paul Tesar (Genetics), Harsh Mathur (Physics) Routing Light with Spatial Solitons: Light Localization and Steering in Liquid Crystals – Antonio DeLuca Mon. February 4th, 2013 12:30 pm-1:30 pm Nematic Liquid Crystals (NLCs) support strong nonlinear effects, most of them due to the high birefringence and non-local response. Light self-confinement via reorientational nonlinearity and nonlocality, yields to the creation of robust light filaments named ‘optical spatial solitons’, which can trap, switch and route optical signals. In the last ten years, the attention to NLC systems, due to their large and polarization dependent nonlinearity, allowed the observation of self-focusing and spatial solitons with a significant attention devoted to reduce thermal contributions to the nonlinear phenomena and lower the required optical power. In all the observed cases, self-confinement was observed over short distances (hundreds of micrometers) and with non-negligible thermo-optic effects. Continue reading… Routing Light with Spatial Solitons: Light Localization and Steering in Liquid Crystals – Antonio DeLuca 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. Continue reading… Unifying theory for universal quake statistics: from compressed nanopillars to earthquakes – Karin Dahmen 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. So the average value in the other envelope is 1.25 X. Continue reading… The Two-Envelope Paradox – Edwin Meyer 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. Continue reading… Unparticles in Strongly Correlated Electron Matter – Philip Phillips 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. Continue reading… Unveiling the Mystery of Mass – Christoph Paus Odd tensor modes from particle production during inflation – Lorenzo Sorbo Tue. December 4th, 2012 11:30 am-12:30 pm Several mechanisms can lead to production of particles during primordial inflation. I will review how such a phenomenon occurs and I will discuss how it can lead to the generation of tensor modes with unusual properties that might be detected in the not-so-far future. The gravitational waves produced this way can have a larger amplitude than in the standard scenarios, can violate parity, and their spectrum can display a feature that can be directly detected within the decade by second-generation gravitational interferometers such as advanced LIGO. Continue reading… Odd tensor modes from particle production during inflation – Lorenzo Sorbo Terahertz plasmons and magnetoplasmons in graphene – Hugen Yan Mon. December 3rd, 2012 12:30 pm-1:30 pm Plasmons in metal surfaces and clusters have been extensively studied due to their potential applications in sensing, imaging, light harvesting and optical metamaterials. Graphene is a semimetal with tunable conductivity and hence can support plasmons as well. In addition to the tunability, graphene plasmons have relatively weak damping due to the high carrier mobility. In this talk, I will present our recent progress on the plasmon excitations in graphene micro-structures and their behavior in an external high magnetic field. We demonstrated graphene plasmonic terahertz filters and polarizers with graphene/insulator stacks and revealed the unique properties of Dirac plasmons with and without a magnetic field. Continue reading… Terahertz plasmons and magnetoplasmons in graphene – Hugen Yan 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. Continue reading… Statics and Dynamics of Colloidal Particles in Liquid Crystals – Oleg Lavrentovich Quantum Dots and Magnetic Quantum Dots for Biomedical Imaging and Separations – Jessica Winter Mon. November 26th, 2012 12:30 pm-1:30 pm Quantum dots, semiconductor nanocrystals, have unique optical properties, including narrow emission bandwidths, broad excitation spectra, and remarkable photostability, which have made them excellent candidates for biological imaging. Since their introduction into the biological milieu in 1998, they have been applied for in vitro and in vivo imaging, diagnostic testing, and multiplexing. As researchers have appreciated the benefits of quantum dots for imaging, emphasis has shifted to fabricating nanocomposites containing quantum dots, and among these magnetic quantum dots have attracted significant attention. Here, we describe our efforts to fabricate quantum dots and magnetic quantum dots. Highlighting our most recent efforts in this area, Continue reading… Quantum Dots and Magnetic Quantum Dots for Biomedical Imaging and Separations – Jessica Winter Advances in Solving the Two-Body Problem in General Relativity: Implications for the Search of Gravitational Waves – Alessandra Buonanno Tue. November 20th, 2012 11:30 am-12:30 pm Compact binary systems composed of black holes and neutron stars are among the most promising sources for ground-based gravitational-wave detectors, such as the Laser Interferometer Gravitational Wave Observatory (LIGO) and its international partners. A detailed and accurate understanding of the shape of the gravitational waves is crucial not only for the initial detection of such sources, but also for maximizing the information that can be obtained from the gravitational-wave signals once they are observed. In this talk I will review progresses at the interface between analytical and numerical relativity. These advances have deepened our understanding of the two-body problem in general relativity, Continue reading… Advances in Solving the Two-Body Problem in General Relativity: Implications for the Search of Gravitational Waves – Alessandra Buonanno Quench dynamics in one-dimensional systems – Aditi Mitra Mon. November 19th, 2012 12:30 pm-1:30 pm How an interacting many-particle system which is initially out of equilibrium evolves in time, is a challenging question, especially for large system sizes where numerical simulations are difficult. The most puzzling issue is understanding the onset of thermalization, a process in which the system completely looses memory of its initial state, with the long time behavior characterized by only one or two parameters. Understanding this issue is important as ideal, thermally isolated systems, and their time-evolution can now be routinely studied in experiments. Using a novel time-dependent renormalization group approach I will show how a reduced part of a strongly interacting system can look effectively classical (or thermal) by being characterized by a dissipation and a noise, Continue reading… Quench dynamics in one-dimensional systems – Aditi Mitra 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. Continue reading… Nuclear Q & A – William Fickinger Effective Field Theory for Fluids – Rachel Rosen Tue. November 13th, 2012 11:30 am-12:30 pm In this talk I will present the low-energy effective field theory that describes the infrared dynamics of non-dissipative fluids. In particular, I will use the techniques of non-linear realizations developed by Callan, Coleman, Wess and Zumino, and Volkov to construct the effective theory based on the symmetry-breaking pattern of the fluid. I will discuss how this formalism can be used to incorporate quantum anomalies into the effective field theory. Continue reading… Effective Field Theory for Fluids – Rachel Rosen Playing with monomolecular layers: model biological systems and liquid crystal alignment layers – Elizabeth Mann Mon. November 12th, 2012 12:30 pm-1:30 pm Self-assembly within biological membranes controls structure, from the nano- to the microscale. The same physical processes also apply to synthetic systems. Here, I survey two different model systems for structure and dynamics within molecularly thin films. Continue reading… Playing with monomolecular layers: model biological systems and liquid crystal alignment layers – Elizabeth Mann 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. Continue reading… Electro-active polymers and high-power-density energy storage – Jerry Bernholc Recent Results from CDMS II and The SuperCDMS Dark-matter Program – Raymond Bunker Tue. November 6th, 2012 11:30 am-12:30 pm The Cryogenic Dark Matter Search experiment (CDMS II) was designed to directly detect dark matter by simultaneously measuring phonon and ionization signals caused by particle interactions in semiconductor targets, allowing event-by-event discrimination of signal from background via the relative sizes of the two signals. I’ll briefly review the CDMS II experiment and then focus on recent results related to the current low-mass WIMP controversy, including data from the CoGeNT, CRESST II, and DAMA/LIBRA experiments that hint at a low-mass WIMP signal and the (similarly sensitive) low-threshold and annual-modulation analyses performed by the CDMS II collaboration. I’ll also comment on the Collar and Fields likelihood analysis of the CDMS II low-energy data. Continue reading… Recent Results from CDMS II and The SuperCDMS Dark-matter Program – Raymond Bunker Half Metallic Ferromagnetism in Complex Oxides and Implications for Spintronics – Nandini Trivedi Mon. November 5th, 2012 12:30 pm-1:30 pm I will discuss the mechanism behind the remarkable properties of double perovskites like Sr2FeMoO6 that show half-metallic ground states with 100% polarization and a ferromagnetic Tc above room temperature. I will conclude with a broad overview of other remarkable properties that can be achieved by changing the transition metal atoms. Reference: O. Erten, et. al Phys. Rev. Lett. 107, 257201 (2011). Continue reading… Half Metallic Ferromagnetism in Complex Oxides and Implications for Spintronics – Nandini Trivedi 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, Continue reading… Biosensing with Magnetic Nanoparticles – John Weaver FUNCTIONAL FILMS AND CERAMICS – Alp Sehirlioglu Mon. October 29th, 2012 12:30 pm-1:30 pm The presentation summarizes our recent efforts in developing new functional materials with a focus on operation in extreme environments. Discussion will include both fundamental aspects of behavior and the path to next generation of devices and applications. Two main topics will be discussed: (i) Oxide based heterointerfaces: Formation of a two dimensional conducting interface between two perovskite insulators (i.e., LaAlO3 on SrTiO3) was first reported in 2004. In 2006 it was reported for the first time that the conductivity of the hetero-interface could be switched between two states by application of an external field (analogous to gate voltage). This technologically significant but still infant discovery holds great potential for next-generation extreme environment electronics that can have both (i) higher information density and (ii) larger operation domain. Continue reading… FUNCTIONAL FILMS AND CERAMICS – Alp Sehirlioglu 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. Continue reading… The First Quasars in Cosmic Structure Formation – Tiziana DiMatteo Qubit-Coupled Mechanics – Matt LaHaye Mon. October 22nd, 2012 12:30 pm-1:30 pm There is a rapidly growing effort to integrate quantum technologies with mechanical structures in order to manipulate and measure quantum states of mechanics for applications ranging from quantum computing to sensing of weak forces to fundamental explorations of quantum mechanics at massive scales. A central focus of this effort, informally dubbed quantum electromechanical systems, has been the integration of superconducting electronics as control and measurement elements in nano and microelectromechanical systems (NEMS and MEMS). In fact, in just the last few years, spectacular advancements have been made in this area, providing researchers with a suite of tools for preparing, manipulating and measuring NEMS and MEMS near and even in the quantum domain. Continue reading… Qubit-Coupled Mechanics – Matt LaHaye Michelson Postdoc Prize talk 3:Many-body interactions in two-dimensional crystals – KinFai Mak Fri. October 19th, 2012 12:30 pm-1:30 pm The problem of electrons in 2D is one of the most important topics in contemporary condensed matter physics. Coulomb interactions between charge carriers in 2D are dramatically enhanced with the much-reduced dielectric screening compared to their bulk counterpart. Recent advances in the development of atomically thin layers of materials have opened up new opportunities for the study of many-body effects in 2D. In the last talk, we will discuss the observations of strong excitonic effects in graphene and in a valley Hall semiconductor through optical spectroscopy. We will demonstrate the control of Coulomb interactions in such atomic membranes by tuning their dielectric screening through an electrostatic gate. Continue reading… Michelson Postdoc Prize talk 3:Many-body interactions in two-dimensional crystals – KinFai Mak Manybody interactions in two-dimensional crystals – Kin Fai Mak Fri. October 19th, 2012 2:30 pm-3:30 pm The problem of electrons in 2D is one of the most important topics in contemporary condensed matter physics. Coulomb interactions between charge carriers in 2D are dramatically enhanced with the much-reduced dielectric screening compared to their bulk counterpart. Recent advances in the development of atomically thin layers of materials have opened up new opportunities for the study of many-body effects in 2D. In the last talk, we will discuss the observations of strong excitonic effects in graphene and in a valley Hall semiconductor through optical spectroscopy. We will demonstrate the control of Coulomb interactions in such atomic membranes by tuning their dielectric screening through an electrostatic gate. Continue reading… Manybody interactions in two-dimensional crystals – Kin Fai Mak 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. Continue reading… Beyond graphene: band insulators and topological insulators – Kin Fai Mak Beyond graphene: band insulators and topological insulators – Kin Fai Mak Thu. October 18th, 2012 4:15 pm-5:15 pm Beyond graphene, there exists a rich family of two-dimensional crystals with a broad spectrum of electronic properties, which remain largely unexplored. For instance, a valley Hall semiconductor emerges by breaking the sublattice symmetry in the honeycomb structure. I will present our recent study of monolayer molybdenum disulfide as a protocol. The observation of an indirect-to-direct band gap crossover in the 2D limit and the optical orientation of its long-lived coupled valley-spins will be discussed. Furthermore, in some of the small band gap semiconductors with strong spin-orbit coupling, a new insulating phase with topologically protected surface states appears due to inverted conduction and valence orbitals. Continue reading… Beyond graphene: band insulators and topological insulators – Kin Fai Mak Michelson Postdoc Prize talk 2:Optics with Dirac electrons – KinFai Mak Tue. October 16th, 2012 12:30 pm-1:30 pm Optical spectroscopy provides an excellent means of understanding the distinctive properties of electrons in the two-dimensional system of graphene. Within the simplest picture, one has a zero-gap semiconductor with direct transitions between the well-known conical bands. This picture gives rise to a predicted frequency-independent absorption of \pi\alpha = 2.3%, where \alpha is the fine-structure constant. We will demonstrate that this relation is indeed satisfied in an appropriate spectral range in the near infrared, but that at higher photon energies electron-hole interactions significantly modify this result through the formation of saddle-point excitons. Optical spectroscopy also permits a detailed analysis of how the linear bands of graphene, Continue reading… Michelson Postdoc Prize talk 2:Optics with Dirac electrons – KinFai Mak Optics with Dirac electrons – Kin Fai Mak Tue. October 16th, 2012 12:30 pm-1:30 pm Optical spectroscopy provides an excellent means of understanding the distinctive properties of electrons in the two-dimensional system of graphene. Within the simplest picture, one has a zero-gap semiconductor with direct transitions between the well-known conical bands. This picture gives rise to a predicted frequency-independent absorption of pi alpha = 2.3 %, where alpha is the fine-structure constant. We will demonstrate that this relation is indeed satisfied in an appropriate spectral range in the near infrared, but that at higher photon energies electron-hole interactions significantly modify this result through the formation of saddle-point excitons. Optical spectroscopy also permits a detailed analysis of how the linear bands of graphene, Continue reading… Optics with Dirac electrons – Kin Fai Mak Michelson Postdoc Prize talk 1:Novel two-dimensional systems: graphene and beyond – KinFai Mak Mon. October 15th, 2012 12:30 pm-1:30 pm The past few years have witnessed a surge of activities in the study of graphene, a stable sheet comprised of just a single atomic layer of carbon atoms in a honeycomb lattice structure. Indeed, 2010 Nobel Physics Prize recognized two researchers for their pioneering contributions to this field. In this talk we will describe the development of the field and some of the reasons for the intense interest in this new material system, highlighting its unusual electronic dispersion and its distinctive mechanical and chemical properties. We will also discuss recent advances in the fabrication and investigation of other 2D atomic membranes. Continue reading… Michelson Postdoc Prize talk 1:Novel two-dimensional systems: graphene and beyond – KinFai Mak Novel two-dimensional systems: graphene and beyond – Kin Fai Mak Mon. October 15th, 2012 4:15 pm-5:15 pm The past few years have witnessed a surge of activities in the study of graphene, a stable sheet comprised of just a single atomic layer of carbon atoms in a honeycomb lattice structure. Indeed, 2010 Nobel Physics Prize recognized two researchers for their pioneering contributions to this field. In this talk we will describe the development of the field and some of the reasons for the intense interest in this new material system, highlighting its unusual electronic dispersion and its distinctive mechanical and chemical properties. We will also discuss recent advances in the fabrication and investigation of other 2D atomic membranes. Continue reading… Novel two-dimensional systems: graphene and beyond – Kin Fai Mak 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. Continue reading… Gamma-ray Pulsars with the Fermi Gamma-ray Space Telescope [joint with Astronomy] – David J. Thompson Kicking Chameleons: Early Universe Challenges for Chameleon Gravity – Adrienne Erickcek Tue. October 9th, 2012 11:30 am-12:30 pm Chameleon gravity is a scalar-tensor theory that mimics general relativity in the Solar System. The scalar degree of freedom is hidden in high-density environments because the effective mass of the chameleon scalar depends on the trace of the stress-energy tensor. In the early Universe, when the trace of the stress-energy tensor is nearly zero, the chameleon is very light and Hubble friction prevents it from reaching its potential minimum. Whenever a particle species becomes non-relativistic, however, the trace of the stress energy tensor is temporarily nonzero, and the chameleon begins to roll. I will show that these “kicks” to the chameleon field have catastrophic consequences for chameleon gravity. Continue reading… Kicking Chameleons: Early Universe Challenges for Chameleon Gravity – Adrienne Erickcek Multiferroic vortices in hexagonal manganites – Weida Wu Mon. October 8th, 2012 12:30 pm-1:30 pm Topological defects are pervasive in complex matter such as superfluids, liquid crystals, and early universe. They have been fruitful playgrounds for many emergent phenomena. Recently, vortex-like topological defects with six interlocked structural antiphase and ferroelectric domains merging into a vortex core were revealed in multiferroic hexagonal manganites. Numerous vortices are found to form an intriguing self-organized network, and may be used to test Kibble-Zurek model of early universe. Furthermore, emergent conduction and piezoelectric properties were observed in charged ferroelectric domain walls protected by topological defects. More excitingly, unprecedented alternating uncompensated magnetic moments were discovered at coupled antiferromagnetic-ferroelectric domain walls in hexagonal manganites, Continue reading… Multiferroic vortices in hexagonal manganites – Weida Wu 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. Continue reading… Decades of Achievement — a tribute to nine of our number having birthdays ending in a zero – Various A new window on primordial non-Gaussianity – Enrico Pajer Tue. October 2nd, 2012 11:30 am-12:30 pm We know very little about primordial curvature perturbations on scales smaller than about a Mpc. I review how mu-type distortion of the Cosmic Microwave Background spectrum provides the unique opportunity to probe these scales over the unexplored range from 50 to104 Mpc-1$. This is a very clean probe, in that it relies only on well-understood linear evolution. While mu-distortion by itself can constrain the amount of power on small scales, correlations between mu-distortion and temperature anisotropies can be used to test Gaussianity. In particular the muT cross correlation is proportional to the very squeezed limit of the primordial bispectrum and hence measures$f_NL\$ local, Continue reading… A new window on primordial non-Gaussianity – Enrico Pajer Into the flat land: Transport studies of ultra-dilute GaAs two-dimensional hole systems in zero field – Jian Huang Mon. October 1st, 2012 12:30 pm-1:30 pm Low temperature charge transport studies of high purity electron systems encompass fundamental subjects of disorder and electron-electron interaction. 50 years after Anderson’s theory of localization for non-interacting electrons, the question on whether and how electron-electron interaction qualitatively alters the picture is still unsettled. Fascinating subjects on interaction-driven phenomena such as Wigner crystallization of electrons (for the quantum scenario) have never been demonstrated. Experimentally, high-purity semiconductor bulk materials offer a desirable tunability of charge density down to ultra-dilute limits where both new frontiers of physics and important applications such as quantum information technologies can be explored. However, such a transition is often overshadowed by the substantial disorder which competes with or even dominates over interaction by rendering the system into an Anderson insulator. Continue reading… Into the flat land: Transport studies of ultra-dilute GaAs two-dimensional hole systems in zero field – Jian Huang “How we fixed the Hubble Space Telescope” – James Breckinridge Thu. September 27th, 2012 4:15 pm-5:15 pm Continue reading… “How we fixed the Hubble Space Telescope” – James Breckinridge The Canadian Hydrogen Intensity Mapping Experiment (CHIME) – a new tool to probe the dark energy driven expansion history of the universe from z=1-3 – Matt Dobbs Tue. September 25th, 2012 11:30 am-12:30 pm The most surprising discovery in cosmology since Edwin Hubble observed the expansion of the Universe isthat the rate of this expansion is accelerating. This either signals that a mysterious Dark Energy dominatesthe energy density of the Universe, or that our understanding of gravity on large scales is incorrect. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) will produce the largest volume astronomical survey to date, potentially unlocking the mysteries the dark-energy driven expansion history of the Universe. The CHIME telescope forms an image of the entire over-head sky each night by digitally processing the information received on a compact array of 2500 radio receivers. Continue reading… The Canadian Hydrogen Intensity Mapping Experiment (CHIME) – a new tool to probe the dark energy driven expansion history of the universe from z=1-3 – Matt Dobbs Valley-Electronics in 2D Crystals – Di Xiao Mon. September 24th, 2012 12:30 pm-1:30 pm In many crystals the Bloch bands have inequivalent and well separated energy extrema in the momentum space, known as valleys. The valley index constitutes a well-defined discrete degree of freedom for low-energy carriers that may be used to encode information. This has led to the concept of valleytronics, a new type of electronics based on manipulating the valley index of carriers. In the first part of the talk, I will describe a general scheme based on inversion symmetry breaking to control the valley index, using graphene and monolayers of MoS2 as an example. In particularly, the valley Hall effect and valley-dependent optical selection will be discussed. Continue reading… Valley-Electronics in 2D Crystals – Di Xiao Non-Gaussianity from general inflationary states – Nishant Agarwal Tue. September 18th, 2012 11:30 am-12:30 pm I will describe the effects of non-trivial initial quantum states for inflationary fluctuations within the context of the effective field theory for inflation. We find that besides giving rise to large non-Gaussianities from inflation, general initial states can also have interesting implications for the consistency relation of the bispectrum. In addition, they leave a distinct observable signature on the scale-dependence of the bias of dark matter halos. I will also discuss constraints on the initial state from current large scale structure data, including luminous red galaxies and quasars in the Sloan Digital Sky Survey sample. Continue reading… Non-Gaussianity from general inflationary states – Nishant Agarwal Novel Ferroelectric Polymers as High Energy Density and Low Loss Dielectrics – Lei Zhu Mon. September 17th, 2012 12:30 pm-1:30 pm The state-of-the-art polymer dielectrics have been limited to nonpolar polymers with relatively low energy density and ultra low dielectric losses for the past decades. With the fast development of power electronics in pulsed power and power conditioning applications, there is a need for next generation dielectric capacitors in areas of high energy density/low loss and/or high temperature/low loss polymer dielectrics. Given limitations in further enhancing atomic and electronic polarizations for polymers, this perspective article focuses on a fundamental question: Can orientational polarization in polar polymers be utilized for high energy density and low loss dielectrics? Existing experimental and theoretical results have suggested the following perspectives. Continue reading… Novel Ferroelectric Polymers as High Energy Density and Low Loss Dielectrics – Lei Zhu 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’ Continue reading… Gate Controlled Spin-Orbit Interaction and 1D Thermoelectric Transport in InAs Nanowires – Xuan Gao Boosting the Universe: Observational consequences of our motion – Amanda Yoho Tue. September 11th, 2012 11:30 am-12:30 pm The Cosmic Microwave Background (CMB), photons from the earliest epoch that are able to free stream towards us, provides a unique opportunity to learn about many properties of the universe we live in. Already, the temperature fluctuations of the CMB have been studied by the Wilkinson Anisotropy Probe (WMAP) and have allowed many cosmological parameters to be pinned down to within a percent error. However, there are many more mysteries to be uncovered by precise measurements of the CMB polarization of these photons and weak lensing fields. Only with a robust understanding of the possible contaminants and astrophysical effects that can deform the measured fields will we be able to accurately characterize which models are favored over others. Continue reading… Boosting the Universe: Observational consequences of our motion – Amanda Yoho Interfacial Charge Transfer in Nanomaterial Based Light Harvesting Devices – Mat Sfire Mon. September 10th, 2012 12:30 pm-1:30 pm We purposefully design and study “molecular-like” interfacial interactions between the multidimensional nanometer-scale building blocks that compose larger-scale functional light harvesting devices. Using time-resolved optical spectroscopy, we aim to understand the nature of discrete interfacial electronic states and their role as crucial intermediates promoting efficient interactions between extended systems (e.g., charge transfer). Our research has suggested the importance of such intermediate interfacial states in both hard and soft nanomaterial heterostructures, including semiconductor quantum dots and organic semiconductors. We aim to understand the fundamental impact of “molecular-like” interfacial states on macroscopic material properties, such as charge transport and light harvesting. For example, Continue reading… Interfacial Charge Transfer in Nanomaterial Based Light Harvesting Devices – Mat Sfire 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! Continue reading… The Intersection between Science and Politics: How Science is Used and Abused in Congress – Chris Martin The interplay between high and low redshift universe – Azadeh Moradinezhad Dizgah Tue. September 4th, 2012 11:30 am-12:30 pm Download the slides Continue reading… The interplay between high and low redshift universe – Azadeh Moradinezhad Dizgah 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, Continue reading… Development of the II-IV Nitride Semiconductors; Considerations from Science, Technology and Sociology – Kathy Kash Supersymmetry, Naturalness, and the LHC: Where Do We Stand? – Matthew Reece Tue. May 1st, 2012 11:30 am-12:30 pm The LHC has accumulated a large luminosity and has already begun ruling out a wide range of theoretical scenarios. I will discuss the theoretical implications of current LHC searches for supersymmetry and the first tentative Higgs measurements. In particular, I will assess the current status of SUSY naturalness, and explain some ways in which searches for the scalar top quark might help to further constrain the parameter space. Continue reading… Supersymmetry, Naturalness, and the LHC: Where Do We Stand? – Matthew Reece Optical Material Science: Electrodynamics of Nanoscale Assembly, and Lifetime and Degradation Science for Photovoltaics – Roger H. French Mon. April 30th, 2012 12:30 pm-1:30 pm The optical properties and electronic structure of materials are critical to the development of new optical materials,(1) novel processes of nanoscale assembly, and the viability of advanced energy technologies. They are the origin of the electrodynamic van der Waals-London dispersion (vdW-Ld) interactions (2) which play a universal role in wetting, interfacial energies, and nanoscale assembly.(3) The challenge of nanotechnology is for science to span more than nine orders of magnitude in dimension. Advanced energy technologies, with their 25 or 50 year capital lifetimes, challenge us to span 24 orders of magnitude in time so as to control degradation processes, damage accumulation, Continue reading… Optical Material Science: Electrodynamics of Nanoscale Assembly, and Lifetime and Degradation Science for Photovoltaics – Roger H. French 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. Continue reading… Smectics! – Randall Kamien Gravitational Wave Detection with Pulsars: the NANOGrav collaboration – Dan Stinebring Tue. April 24th, 2012 11:30 am-12:30 pm The effort to detect long-wavelength gravitational waves with a pulsar timing array (PTA) is progressing well, with three major international groups intensifying their efforts and increasingly sharing data and techniques. *Your* PTA, the North American Nanohertz Observatory for Gravitational waves (NANOGrav) is making excellent progress. I will report on our recent results and also comment on my group’s specialty, the effort to remove time variable propagation delays through the ionized interstellar medium. Continue reading… Gravitational Wave Detection with Pulsars: the NANOGrav collaboration – Dan Stinebring Magnetoresistance in Two Dimensions – Arnold J. Dahm Mon. April 23rd, 2012 12:30 pm-1:30 pm We present measurements of the magnetoresistivity of a weakly interacting 2D electron liquid in an unexplored region near the boundary of the 2D electron gas supported by a liquid helium surface. The magnetoresistivity is calculated by Dykman in the self-consistent Born approximation. For fields greater than a field B0, the magnetoresistivity is proportional to (muB)^3/2, where mu is the mobility. Electron-electron interactions cause a crossover to the Drude behavior as the density is increased. All of our data scale with the density-dependent parameter B0 as B/B0, with the magnitude of the magnetoresistivity scaled as 1/n. For low electron densities and fields less that B0, Continue reading… Magnetoresistance in Two Dimensions – Arnold J. Dahm 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]. Continue reading… Combining superconductors and ferromagnets: a new type of symmetry? – Norman Birge Hunting for de Sitter vacua in the String Landscape – Gary Shiu Tue. April 17th, 2012 11:30 am-12:30 pm Results from observational cosmology suggest that our universe is currently accelerating. The simplest explanation is that we are living in a universe with a positive cosmological constant. In this talk, I will describe some recent attempts in constructing such solutions in string theory and discuss the difficulties one encounters in finding metastable de Sitter vacua. Thus, the requirement of positive cosmological constant and stability imposes strong constraints on the string theory landscape. Continue reading… Hunting for de Sitter vacua in the String Landscape – Gary Shiu Electronic structure of disordered solids – David A. Drabold Mon. April 16th, 2012 12:30 pm-1:30 pm Understanding the physics of structurally disordered materials is a challenge to experimentalists and theorists alike. In this talk, I discuss the character of electronic states in disordered materials and emphasize the interplay between structure and electronic properties. I begin by discussing the consequences of atomic structural disorder on electron states. As shown long ago by Anderson, disorder in atomic coordinates creates spatially confined or “localized” electron eigenstates near the Fermi level. I explore these states with large and realistic structural models and suitable electronic structure techniques. I begin with the structure of electron states in large and realistic models of a-Si, Continue reading… Electronic structure of disordered solids – David A. Drabold 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. Continue reading… Stars, galaxies and cosmology in the nearby Universe [joint with Astronomy] – Alan McConnachie Bosonic and Fermionic Non-thermal Dark Matter Isocurvature Perturbations and Non-Gaussianities – Daniel Chung Tue. April 10th, 2012 11:30 am-12:30 pm Dark matter candidates in a broad class of non-thermal models produce primordial isocurvature perturbations and non-Gaussianities. We discuss the model dependence of such scenarios. In particular, fermionic superheavy dark matter requires non-gravitational interactions to be observationally interesting. We also present a general mathematical result regarding the cross correlation between the primordial isocurvature perturbations and curvature perturbations. This last result is of general interest for isocurvature phenomenology. Download the slides Continue reading… Bosonic and Fermionic Non-thermal Dark Matter Isocurvature Perturbations and Non-Gaussianities – Daniel Chung 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), Continue reading… Lasers and Anti-lasers – A. Douglas Stone Ghost-free multi-metric interactions Tue. April 3rd, 2012 11:30 am-12:30 pm The idea that the graviton may be massive has seen a resurgence of interest due to recent progress which has overcome its traditional problems. I will review this recent progress, and show how the theory can be extended to write consistent interactions coupling together multiple massive spin-2 fields. Download the slides Continue reading… Ghost-free multi-metric interactions The role of molecular beam epitaxy in fundamental physics through an example: assessing the impact of disorder on the v=5/2 fractional quantum Hall effect – Mike Manfra Fri. March 30th, 2012 11:30 am-12:30 pm Thirty years after its initial discovery, the fractional quantum Hall effect continues to challenge our understanding of electronic correlations in low dimensions. Throughout this history advances in molecular beam epitaxy (MBE) have played an important role. Presently, the fragile v=5/2 fractional quantum Hall state is the subject of intense scrutiny. It is theoretically conjectured that the v=5/2 state is described by the Moore-Read Pfaffian wavefunction, possessing excitations obeying non-Abelian braiding statistics. If experimentally confirmed, excitations with non-Abelian braiding statistics may provide a platform for proposed schemes of topologically-protected quantum computing. While there are many aspects to the physics at v=5/2, Continue reading… The role of molecular beam epitaxy in fundamental physics through an example: assessing the impact of disorder on the v=5/2 fractional quantum Hall effect – Mike Manfra 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, Continue reading… The Life and Death of a Drop: Topological Transitions and Singularities – Sidney Nagel Chromo-Natural Inflation – Peter Adshead Tue. March 27th, 2012 11:30 am-12:30 pm I will describe a new model for inflation – Chromo-Natural Inflation – consisting of an axionic scalar field coupled to a set of three non-Abelian gauge fields. The model’s novel requirement is that the gauge fields begin inflation with a rotationally invariant vacuum expectation value (VEV) that is preserved through identification of SU(2) gauge invariance with rotations in three dimensions. The gauge VEV interacts with the background value of the axion, leading to an attractor solution that exhibits slow roll inflation even when the axion decay constant has a natural value (\less M_{\rm Pl}). Assuming a sinusoidal potential for the axion, Continue reading… Chromo-Natural Inflation – Peter Adshead Micro and Nano Technology at the Lurie Nanofabrication Facility – Robert Hower Fri. March 23rd, 2012 12:30 pm-1:30 pm This seminar will give an overview of micro and nano technologies at the University of Michigan Lurie Nanofabrication Facility (LNF). In addition, we will present examples of research accomplishments and applications of these technologies in diverse fields including but not limited to Electrical Engineering, Physics, Life Sciences, Biomedical Engineering and Chemical Engineering. Operated by the University of Michigan Solid-State Electronics Laboratory (SSEL), the LNF has extensive experience in microelectronics, micromechanics, optoelectronics, and micro and nano technologies based on silicon, compound semiconductor, and organic materials. It offers a complete laboratory for the fabrication of nanofabricated semiconductor and polymer electronic and optoelectronic devices and circuits, Continue reading… Micro and Nano Technology at the Lurie Nanofabrication Facility – Robert Hower 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, Continue reading… Multilayer Polymer Photonics: From “Origami” Lasers to Optical Data Storage to Cavity Polaritons – Ken Singer Testing the concordance cosmology with weak gravitational lensing – Ali Vanderveld Tue. March 20th, 2012 11:30 am-12:30 pm Weak gravitational lensing, whereby the images of background galaxies are distorted by foreground matter, can be a powerful cosmological probe if systematics are sufficiently controlled. In particular, I will show how we may use weak lensing to robustly test the standard cosmological constant-dominated “concordance model” of cosmology by using in-hand expansion history data to make predictions for future observations. I will then discuss one recent proposal for economically gathering the necessary data while minimizing systematics — the balloon-borne High Altitude Lensing Observatory (HALO). Download the slides Continue reading… Testing the concordance cosmology with weak gravitational lensing – Ali Vanderveld Anisotropic response in molecular crystals and the development of Modulated Orientation Sensitive Terahertz Spectroscopy (MOSTS) – Andrea Markelz Mon. March 19th, 2012 12:30 pm-1:30 pm Since the mid 1980’s there have been predictions of protein structural vibrations with ~ 1meV energies, which corresponds to the terahertz frequency range. These large scale motions involve the correlated movement of many atoms and are associated with the conformational motions involved in protein function. There have been many attempts to measure these modes, but the energy range overlaps with that of local librational motions of the surface side chains and the solvent, and these contributions give rise to a strong glass-like response. In this talk I will discuss our development of a technique to isolate the large scale structural contribution from a glassy background called Modulated Orientation Sensitive Terahertz Spectroscopy (MOSTS). Continue reading… Anisotropic response in molecular crystals and the development of Modulated Orientation Sensitive Terahertz Spectroscopy (MOSTS) – Andrea Markelz III-Nitride Light-Emitting Diodes for Solid-State Lighting – Hongping Zhao Mon. March 12th, 2012 12:30 pm-1:30 pm Energy efficiency and renewable energy technologies have significant importance for achieving sustainable energy systems in modern society. Lighting accounts for more than 22% of the total electrical energy usage in US, and technologies based on solid state lighting (SSL) utilizing semiconductor-based material has tremendous promise to replace the existing lighting devices. As compared to traditional incandescent and fluorescent lamps, SSL is more energy-efficient, reliable, and environmentally-friendly. Once widely used, SSL could lead to the decrease of worldwide electricity consumption for lighting by >50% and reduces total electricity consumption by >10%. The U.S. Department of Energy describes SSL as a pivotal emerging technology that promises to fundamentally alter lighting in the future. Continue reading… III-Nitride Light-Emitting Diodes for Solid-State Lighting – Hongping Zhao 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. Continue reading… The Red Revolution: How Seismology of Red Giants is Transforming Stellar Physics and Stellar Population Studies [joint with Astronomy] – Marc Pinsonneault HgTe as a Topological Insulator – Laurens Molenkamp Mon. March 5th, 2012 12:30 pm-1:30 pm HgTe is a zincblende-type semiconductor with an inverted band structure. While the bulk material is a semimetal, lowering the crystalline symmetry opens up a gap, turning the compound into a topological insulator. The most straightforward way to do so is by growing a quantum well with (Hg,Cd)Te barriers. Such structures exhibit the quantum spin Hall effect, where a pair of spin polarized helical edge channels develops when the bulk of the material is insulating. Our transport data provide very direct evidence for the existence of this third quantum Hall effect, which now is seen as the prime manifestation of a 2-dimensional topological insulator. Continue reading… HgTe as a Topological Insulator – Laurens Molenkamp An estimator for statistical anisotropy from the CMB bispectrum – Ema Dimstrogiovanni Tue. February 28th, 2012 11:30 am-12:30 pm Various data analysis of the Cosmic Microwave Background (CMB) radiation present anomalous features that can be interpreted as indications of statistical isotropy breaking. Some models of inflation involving vector fields predict statistical anisotropy in the correlation functions of primordial curvature perturbations. We employ a simplified vector field model and parametrize the bispectrum of curvature fluctuations in such a way that all the information about statistical anisotropy is encoded in some coefficients lambda_{LM} (representing the ratio of the anisotropic to the isotropic bispectrum amplitudes). We compute an optimal estimator for these coefficients and their Fisher error. We predict a sensitivity for an experiment like Planck to the anisotropic to isotropic amplitudes of about 10% if fNL is around 30. Continue reading… An estimator for statistical anisotropy from the CMB bispectrum – Ema Dimstrogiovanni 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. Continue reading… Pollockian Mechanics: Painting with Viscous Jets – Andrzej Herczyński Local Primordial non-Gaussianity in Large-scale Structure – Marilena LoVerde Tue. February 21st, 2012 11:30 am-12:30 pm Primordial non-Gaussianity is among the most promising of few observational tests of physics at the inflationary epoch. At present non-Gaussianity is best constrained by the cosmic microwave background, but in the near term large-scale structure data may be competitive so long as the effects of primordial non-Gaussianity can be modeled through the non-linear process of structure formation. I will discuss recent work modeling effects of a few types of primordial non-Gaussianity on the large-scale halo clustering and the halo mass function. More specifically, I will compare analytic and N-body results for two variants of the curvaton model of inflation: (i) a “tau_NL” Continue reading… Local Primordial non-Gaussianity in Large-scale Structure – Marilena LoVerde High Tc superconductivity in cuprates: A status report – Mohit Randeria Fri. February 17th, 2012 12:30 pm-1:30 pm 25 years after their discovery, the microscopic problem of high Tc superconductivity in cuprates is still not “solved”. I will focus on summarizing the experiments that show us that the observed phases, with varying carrier concentration, challenge three paradigms of 20th century condensed matter physics. (i) The parent Mott insulator cannot be understood within band theory; (ii) the superconducting state and phase transition force us to go beyond a BCS mean-field description; and (iii) the “normal” metallic state cannot be described within Landau Fermi liquid theory. I will then briefly describe some of the success in theoretically understanding the superconducting state and indicate open questions about the normal state. Continue reading… High Tc superconductivity in cuprates: A status report – Mohit Randeria 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, Continue reading… Viscosity of Strongly Interacting Fermions – Mohit Randeria Inflation, or What? – William Kinney Tue. February 14th, 2012 11:30 am-12:30 pm Cosmological inflation is the leading candidate theory for the physics of the early universe, and is in beautiful agreement with current cosmological data such as the WMAP Cosmic Microwave Background measurement. I consider alternatives to inflation with a critical eye, and present a simple argument showing that any model which matches the observed universe must have one of three properties: (1) accelerated expansion, (2) speed of sound faster than the speed of light, or (3) super-Planckian energy density. Download the slides Continue reading… Inflation, or What? – William Kinney Quantum Signatures of Optomechanical Instability and Synchronization in Optomechanical Arrays – Jiang Qian Mon. February 13th, 2012 12:30 pm-1:30 pm Optomechanical systems couple light stored in an optical resonant cavity to the motion of a mechanical motion of the cavity walls. Single optomechanical cells have been successfully fabricated in a wide variety of systems. Recent experiments have further demonstrated setups, such as photonic crystal structures, that in principle allow to confine several optical and vibrational modes on a single chip. In the first part of my presentation I will demonstrate the emergence of a robust, long-living and highly non-classical mechanical state in a standard single cell optomechanical setup. I will show that under some parameters, the longtime steady state of the mechanical degrees of freedom has significantly negative Wigner density. Continue reading… Quantum Signatures of Optomechanical Instability and Synchronization in Optomechanical Arrays – Jiang Qian 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, Continue reading… The 2011 Science Nobel Prizes – What were they given for? – Glenn Starkman, Arthur Heuer, and Mansun Sy Quantum Kinetics and Thermalization of Hawking Radiation – Dmitry Podolsky Tue. February 7th, 2012 11:30 am-12:30 pm Hawking’s discovery of black holes radiance along with Bekenstein’s conjecture of the generalized second law of thermodynamics inspired a conceptually pleasing connection between gravity, thermodynamics and quantum theory. However, the discovery that the spectrum of the radiation is in fact thermal, together with the no-hair theorem, has brought along with it some undesirable consequences, most notably the information loss paradox. There have been many proposals to the resolution of this paradox, with the most natural resolution being that during the time of collapse the radiation given off is not completely thermal and can carry small amounts of information with it. Continue reading… Quantum Kinetics and Thermalization of Hawking Radiation – Dmitry Podolsky Condensates and quasiparticles in inflationary cosmology – Daniel Boyanovsky Mon. February 6th, 2012 11:30 am-12:30 pm Correlation functions during inflation feature infrared effects that could undermine a perturbative study. I will discuss self-consistent mechanisms of mass generation that regulates infrared physics, and introduce a method based on quantum optics to obtain the decay width of quantum states. Lack of energy conservation entails that EVERY particle acquires a width as a result of emission and absorption of superhorizon quanta thus becoming “quasiparticles”. BLACKBOARD TALK Continue reading… Condensates and quasiparticles in inflationary cosmology – Daniel Boyanovsky Fe pnictide superconductors – David Singh Mon. February 6th, 2012 12:30 pm-1:30 pm The 2008 discovery of high temperature superconductivity in doped LaFeAsO by Kamihara and co-workers provided the second class of high Tc materials, the other being the cuprate family discovered in 1986 by Bednorz and Mueller. This discovery was revolutionary in that many of the properties of the iron based superconductors are radically different from those of the cuprates, apparently requiring a new and broader understanding of the physics of high temperature superconductivity. The purpose of this talk is to discuss the chemistry and physics of the new superconductors in relation to cuprates. So far, many puzzles remain. The materials appear to be much more band-like and show much stronger signatures of metallic (Fermi surface related) physics than cuprates, Continue reading… Fe pnictide superconductors – David Singh 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. Continue reading… Oriented assembly of microparticles by capillarity – Kate Stebe Gravitational Waves from Cosmological Phase Transitions – Tom Giblin Tue. January 31st, 2012 11:30 am-12:30 pm Cosmological phase transitions occurred. I will talk about recent advances in modeling possible phase transitions when these transitions are mediated by scalar fields. I will discuss first- and second-order transitions, at various scales, and show how we can compute the background of stochastic gravitational waves produced during (and after) these transitions. Continue reading… Gravitational Waves from Cosmological Phase Transitions – Tom Giblin The Incredible Shrinking Tuning Forks – Nanowire Electromechanical Systems at Radio and Microwave Frequencies – Philp Feng Mon. January 30th, 2012 12:30 pm-1:30 pm Nanoscience today enables many fascinating low-dimensional structures and new materials with previously inaccessible properties. Nanostructures with mechanical degrees of freedom offer compelling characteristics that make them interesting for both fundamental studies and technological applications. This talk will describe my collaborative research efforts in exploring vibrating nanowires, and in engineering these very thin nanowires into functional and high-performance nanoscale electromechanical systems (NEMS). I will show NEMS resonators operating in the very-high and ultra-high frequency (VHF/UHF, 30MHz – 3GHz) ranges, based on silicon nanowires enabled by a hybrid bottom-up/top-down process. Exploiting the interesting properties of thin silicon nanowires, we have developed an all-electronic, Continue reading… The Incredible Shrinking Tuning Forks – Nanowire Electromechanical Systems at Radio and Microwave Frequencies – Philp Feng 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. Continue reading… Higgs Boson – on the road to discovery – Sergo Jindariani Spatially Covariant Theories of a Transverse, Traceless Graviton – Godfrey Miller Tue. January 24th, 2012 11:30 am-12:30 pm General relativity is a generally covariant, locally Lorentz covariant theory of two transverse, traceless graviton degrees of freedom. According to a theorem of Hojman, Kuchar, and Teitelboim, modifications of general relativity must either introduce new degrees of freedom or violate the principle of local Lorentz covariance. In this paper, we explore modifications of general relativity that retain the same graviton degrees of freedom, and therefore explicitly break Lorentz covariance. Motivated by cosmology, the modifications of interest maintain explicit spatial covariance. In spatially covariant theories of the graviton, the physical Hamiltonian density obeys an analogue of the renormalization group equation which encodes invariance under flow through the space of conformally equivalent spatial metrics. Continue reading… Spatially Covariant Theories of a Transverse, Traceless Graviton – Godfrey Miller 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. Continue reading… Fundamental Physics from Large-Scale Structure – Dragan Huterer 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. Continue reading… Can that really be so? A light-hearted look at the concept of force in classical, quantum, and statistical mechanics – Philip Taylor Graphene Optics and Electronics – Marcus Freitag Mon. December 5th, 2011 12:30 pm-1:30 pm Graphene is a two-dimensional material with conical bands that touch at the Dirac or Charge-Neutrality point. Its zero bandgap and atomically thin body allow it to switch between n-type and p-type conduction when assembled into a field-effect transistor geometry. The current modulation however is limited due to a finite minimum conductivity at the Charge Neutrality point, which prevents us from using graphene for digital electronic applications. We therefore investigate graphene as an optical and analog electronic material, where the low on-off ratio is less of a problem. Especially the high frequency (RF) electronic applications are promising since graphene can be gated efficiently and has high carrier mobility. Continue reading… Graphene Optics and Electronics – Marcus Freitag Dark matter bounds from direct and indirect searches – Aravind Natarajan Tue. November 22nd, 2011 11:30 am-12:30 pm I discuss ways of constraining dark matter properties using a combination of direct and indirect dark matter measurements. The DAMA, CoGeNT, and CRESST experiments have obtained tentative evidence for low mass WIMPs. I show that the CMB is a clean probe of low mass WIMPs, and the WMAP+SPT measurements place competitive bounds on light WIMPs. I discuss how these dark matter bounds may be further improved by including other data sets, such as counts of galaxy clusters. Continue reading… Dark matter bounds from direct and indirect searches – Aravind Natarajan Charge carrier dynamics in heterostructured semiconductor nanocrystals and nanocrystal solids – Michail Zamkov Mon. November 21st, 2011 12:30 pm-1:30 pm In the first part, I will present a novel strategy for processing of colloidally stable semiconductor nanoparticles (also known as nanocrystals or quantum dots) into all-inorganic solid films, deployable for photovoltaic applications. The method relies on encapsulation of semiconductor nanocrystal arrays within a matrix of a wide-band gap inorganic material, which preserves optoelectronic properties of individual nanoparticles, yet, renders the nanocrystal film photoconductive. The photovoltaic performance of fabricated nanocrystal solids is demonstrated through the development of prototype solar cells exhibiting stable and efficient operation in ambient conditions. The second part of the presentation will focus on ultrafast electron processes taking place in heterostructured nanocrystals comprising metal (Au) and semiconductor (CdS) material domains. Continue reading… Charge carrier dynamics in heterostructured semiconductor nanocrystals and nanocrystal solids – Michail Zamkov 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. Continue reading… Closing In On Dark Matter – Dan Hooper Light does not always travel on the light cone – Yi-Zen Chu Tue. November 15th, 2011 11:30 am-12:30 pm Massless particles such as photons and gravitons do not travel solely on the null cone in a generic curved spacetime. They propagate at all speeds equal to and less than c. This fact does not appear to be well appreciated in cosmology, and its consequences deserve to be worked out to ensure we are interpreting observations correctly. A rather dramatic (and hypothetical) example would be the following: suppose a significant fraction of photons from a distant supernova travels slower than c, then we may be mislead into thinking the SN is dimmer than it actually is, because some of the light has not arrived yet. Continue reading… Light does not always travel on the light cone – Yi-Zen Chu A physicist walks into a biology department… – Robin Snyder Mon. November 14th, 2011 12:30 pm-1:30 pm I present two recent projects in theoretical ecology and point out the connections to math loved by physicists. The first concerns life in a variable environment: when should an organism buffer itself against environmental variation and when should it try to take advantage of environmental variation? The second concerns the viability of mussel populations in a marine reserve network when shifting ocean currents cause fluctuating dispersal between reserves. Continue reading… A physicist walks into a biology department… – Robin Snyder Holographic Quantum Quench – Sumit Das Fri. November 11th, 2011 11:30 am-12:30 pm The holographic correspondence between non-gravitational field theories and gravitational theories in one higher dimension can be used to study non-equilibrium behavior of strongly coupled quantum field theories. One such phenomenon is that of quantum quench, where a coupling of the field theory is time dependent and typically asymptotes to constants at early and late times. In the gravity dual this can describe, under suitable circumstances, either black hole formation, or passage through a spacelilke region of high curvature similar to a cosmological singularity. On one hand this has taught us about the meaning of cosmological singularities, while on the other hand this has thrown light on the process of thermalization in strongly coupled field theories. Continue reading… Holographic Quantum Quench – Sumit Das A Paradise Island for Deformed Gravity – Florian Kuehnel Tue. November 8th, 2011 11:30 am-12:30 pm I will discuss our recently-proposed model (hep-th/1106.3566) of deformations of general relativity that are consistent and potentially phenomenologically viable, since they respect cosmological backgrounds. These deformations have unique symmetries in accordance with unitarity requirements, and give rise to a curvature induced self-stabilizing mechanism. Furthermore, our findings include the possibility of consistent and potentially phenomenologically viable deformations of general relativity that are solely operative on curved spacetime geometries, reducing to Einstein’s theory on the Minkowski background. I will also comment on possible phenomenological implications. Continue reading… A Paradise Island for Deformed Gravity – Florian Kuehnel The search for Majorana Fermions in semiconductor nanowires – Roman Lutchyn Mon. November 7th, 2011 12:30 pm-1:30 pm The exploration of topological phases of matter is one of the main challenges in condensed matter physics. Among the exciting recent developments in this direction are the discoveries of the new phases of matter with many intriguing properties such as topological insulators and superconductors. In my talk, I will focus on topological superconductors and discuss how to realize spinless p-wave superconductivity in semiconductor/superconductor heterostructures. I will show that such a non-trivial topological state emerging at the interface supports zero-energy modes that can be occupied by Majorana fermions. These quasi-particles, which are exotic in the sense that they are at the same time their own antiparticles,