Physics colloquium archive

Fall 2017

September 7, 2017

Victor Yakovenko, University of Maryland

Economic inequality from a statistical physics point of view

Abstract: By analogy with the probability distribution of energy in statistical physics, the probability distribution of money among the agents in a closed economic system is expected to follow the exponential Boltzmann-Gibbs law, as a consequence of entropy maximization. Analysis of empirical data shows that income distributions in the USA, European Union, and other countries exhibit a well-defined two-class structure. The majority of the population (about 97%) belongs to the lower class characterized by the exponential ("thermal") distribution. The upper class (about 3% of the population) is characterized by the Pareto power-law ("superthermal") distribution, and its share of the total income expands and contracts dramatically during booms and busts in financial markets. Such a two-class distribution can be obtained analytically for a combination of additive and multiplicative stochastic processes. Globally, data analysis of energy consumption (and CO2 emission) per capita around the world in the last 30 years shows decreasing inequality and convergence toward the exponential probability distribution, in agreement with the maximal entropy principle. All papers are available at


September 14, 2017

Kip Thorne

Geometrodynamics: Exploring the nonlinear dynamics of curved spacetime via computer simulations and gravitational wave observations

Abstract: A half-century ago, John Wheeler challenged his students and colleagues to explore Geometrodynamics: the nonlinear dynamics of curved spacetime. How does the curvature of spacetime behave when roiled in a storm, like a storm at sea with crashing waves. Dr. Thorne and collaborators tried to explore this, and the failed. Success eluded us until two new tools became available: computer simulations and gravitational wave observations. Dr. Thorne will describe what these have begun to teach us, and he will offer a vision for the future of Geometrodynamics.

About the speaker: Kip Thorne is the Richard P. Feynman Professor of Theoretical Physics, Emeritus, at the California Institute of Technology in Pasadena, California. He is a theoretical physicist specializing in the astrophysical effects of Einstein's General Theory of Relativity, especially black holes and gravitational waves. He was one of the founding members of the Laser Interferometer Gravitational Wave Observatory (LIGO) in 1984. The goal of LIGO is to observe gravitational waves from extreme astrophysical events. Gravitational waves were first predicted by Albert Einstein one-hundred years ago this year. While there is good indirect evidence for gravitational waves based on the behavior of binary pulsars, the first direct measurement of a gravitational wave was announced by the LIGO team on February 11, 2016. Two independent laser interferometers in Livingston, Louisiana and Hanford, Washington observed a gravitational wave on September 14, 2015. Analysis of the signal indicates the wave was produced by the collision of two black holes more than one billion light years away. Professor Thorne is an accomplished author of books for scientists and the general public, and he was the scientific consultant and Executive Producer of the film Interstellar.

Video: Kip Thorne Colloquium at Wayne State on Geometrodynamics


September 21, 2017

Boris Yakobson, Rice University

Predictive modeling of low-dimensional materials, nanotubes, graphene, and beyond

Abstract: Comprehensive tools of materials modeling are derived from the principles of physics and chemistry, empowered by high performance computing. Together, this allows one to make verifiable predictions of novel physical structures with specific, often useful or even extraordinary, properties. Nanotubes offer one such lesson [1], where atomic makeup and defects dynamics lead to the understanding of their strength and failure physics on one hand, while also reveal the origins of chiral symmetry in nano-carbon synthesis [2]. A second, very recent, example is the prediction of pure mono-elemental 2D boron, its particular structures to form on Ag(111), which culminated in recent experimental confirmations. We may also mention, if time permits, its physical properties like new 2D-superconductor [3], now-detected Dirac cone dispersion, still-sought 2D-plasmonics, and catalysis.

[1] M. Davenport, Chemical & Engineering News, 93, 10 (2015) || B.I. Yakobson and R.E. Smalley, American Scientist, 85, 324-337 (1997).

[2] F. Ding et al. Proc. Natl. Acad. Sci., 106, 2506 (2009) || V. Artyukhov et al. Proc. Natl. Acad. Sci. 109, 15136 (2012) || V. Artyukhov et al. Phys. Rev. Lett. 114, 115502 (2015) || V. Artyukhov - E. Penev, et al. Nature Comm. 5, 489 (2014).

[3] Z. Zhang et al. Nature Chem. 8, 525 (2016) || Z. Zhang et al. Angewandte Chemie Int. Ed. 54, 13022 (2015) || E. Penev - A. Kutana et al. Nano Lett. 16, 2522 (2016) || Z. Zhang et al. Nano Lett. 6, 6622 (2016) || A. Brotchie, Nature Reviews, doi:10.1038/natrevmats.2016.83 (2016) || S. Shirodkar, Y. Huang et al. (unpublished) || Y. Liu et al. Nature Energy 2, 17127 (2017).


September 28, 2017

Michael Murray, University of Kansas

There and Back Again: A Journey from classical physics to quantum mechanics and back to classical fields.

Abstract: When the nucleus was discovered it appeared to be a massive classical charged sphere at the heart of the atom. Later protons and neutrons were discovered inside the nucleus. Later still it was found that protons and neutrons are themselves made up of quarks held together by gluons. Such objects are described by quantum field theories. As the energy of our colliders has increased we have found more and more gluons inside the nucleus. At some point we expect the gluons to fuse together into a glass-like state called the Color Glass Condensate. This new state of quantum matter may actually behave like a classical field.


October 5, 2017

Chris Adami, Michigan State University

What quantum optics can tell us about black holes

Abstract: Black holes are astrophysical objects whose reality is beyond doubt. However, many aspects of them remain mysterious because observations are difficult and experiments are impossible. Research in the last two decades has revealed a remarkable analogy between the mathematics of quantum black holes and certain quantum optical systems, which makes it possible to study "black hole analogues" in the lab, and to better understand some of the seemingly paradoxical features of black holes. I review recent breakthroughs in black hole physics that were inspired by the quantum optics analogy, and that has removed some of the paradoxes surrounding black holes.

About the speaker: Dr. Adami is Professor for Microbiology and Molecular Genetics & Physics and Astronomy at Michigan State University in East Lansing, Michigan. As a computational biologist, Dr. Adami's main focus is Darwinian evolution, which he studies theoretically, experimentally, and computationally, at different levels of organization (from simple molecules to brains). He has pioneered the application of methods from information theory to the study of evolution and designed the "Avida" system that launched the use of digital life (mutating and adapting computer viruses living in a controlled computer environment) as a tool for investigating basic questions in evolutionary biology. He was also a Principal Scientist at the Jet Propulsion Laboratory where he conducted research into the foundations of quantum mechanics and quantum information theory. Dr. Adami earned a BS in physics and mathematics and a Diplom in theoretical physics from the University of Bonn (Germany) and MA and Ph.D. degrees in theoretical nuclear physics from the State University of New York at Stony Brook. He wrote the textbook "Introduction to Artificial Life" (Springer, 1998) and is the recipient of NASA's Exceptional Achievement Medal. He was elected a Fellow of the American Association for the Advancement of Science (AAAS) in 2011.


October 12, 2017

Pushpa Bhat (FNAL)

Fifty Years of Particle Physics and Discoveries at Fermilab

Abstract: Fermilab, the premier laboratory for elementary particle physics and accelerator research in the U.S., has been at the forefront of fundamental discoveries for the past fifty years. It has had the distinction of discovering three fundamental particles the bottom and top quarks, and the tau neutrino, as well as leading the detailed exploration of the Standard Model, and making major advances in the pursuit of the Higgs boson. The home of the highest energy proton accelerator and particle collider in the world until the end of the last decade, Fermilab has also led the development of enabling technologies for powerful accelerator facilities. In this talk, I will present the highlights of the past fifty years of particle physics at Fermilab and discuss its future program and role in the new global enterprise of particle physics.

About the speaker: Pushpa Bhat is a senior scientist at Fermi National Accelerator Laboratory (Fermilab), Deputy Head of Fermilab Program Planning, and an Adjunct Professor and graduate faculty at Northern Illinois University. After receiving her Ph.D. in physics from Bangalore University, India, in 1982 and a brief stint as a scientific officer at the Eindhoven University Cyclotron Lab in the Netherlands, she moved to the U.S. and carried out postdoctoral work in experimental high energy physics at Duke University and Fermilab. Her research career has spanned applied physics, nuclear physics, and experimental particle physics, from keV energies to the energy frontier. Bhat is a Fellow of the American Physical Society (APS) and the American Association for the Advancement of Science (AAAS). She has served as the Chair of the APS Forum on Physics and Society (FPS) and as Chair of several committees. She currently serves on the APS Council and on the APS Board of Directors, and as Secretary for the International Committee on Future Accelerators (ICFA).


October 19, 2017

Zhi-Feng Huang, Wayne State University

Exploring microstructures and dynamics of complex systems: Ordering, chirality, defects, and scale coupling

Abstract: One of the long-lasting challenges in the study of advanced materials is how to effectively tackle the vast complexity of the system that is of nonequilibrium nature and involves multiple spatial and temporal scales. Of particular importance is the bridging between material microstructural details and mesoscopic characteristics such as surface patterns or interfacial structures, for which much of recent theoretical effort has been put on the development of novel density-field based approaches across different scales. In this talk, I will discuss some recent advances in this field for modeling material microstructures and dynamics and some of the ongoing challenges. Sample topics include the emergence of ordering phases, the control of 2D structure or pattern chirality and chiral elastic properties, structures and collective dynamics of topological defects in binary 2D materials such as h-BN, and the interface lattice pinning effect during material growth due to the coupling between micro and meso spatial scales.


October 26, 2017

Christopher Kelly, Wayne State University

Nanoscale membrane curvature revealed by polarized localization microscopy

Abstract: Many essential biological processes depend on the interaction of lipids, proteins, and carbohydrates at length scales that are unresolvable by conventional optical microscopes. We have combined super-resolution microscopy methods to create polarized localization microscopy (PLM). With PLM, we have measured membrane curvature as small as 20 nm radii, measured curvature-induced molecular sorting, and a local change in the local membrane viscosity. Further, we have discovered that cholera toxin subunit B self-assembles to form nanoscale membrane buds in quasi-one component bilayers to facilitate its immobilization and internalization into cells. We will discuss the physics of PLM and the mechanisms by which cholera toxin bends membranes.


November 9, 2017

Ken Ritchie, Purdue University

High-speed single molecule tracking of proteins in E. coli

Abstract: All living cells are encapsulated by an outer envelope, which contains a fluid phospholipid-based membrane that structurally delineates the inside of the cell from its environment. Embedded within this membrane is the machinery (proteins) required for the cell to sense and interact with its environment. As such, one expects that there are mechanisms in place to control the location and mobility of the membrane proteins in the fluid membrane in order to perform complex and critical tasks. In this talk, I will present our group's recent single-molecule mobility studies into the (dynamic) organization of the cellular membranes of E. coli bacteria performed at acquisition rates up to 1 kHz. Examples will include the structure of the polar region of the inner membrane as seen by the serine chemoreceptor Tsr and investigations into interactions of the iron transporter FepA in the E. coli outer membrane with the inner membrane protein TonB.

About the speaker: Dr. Ritchie is a professor and the associate head of the Department of Physics and Astronomy at Purdue University. He obtained his Ph.D. at the University of British Columbia in Vancouver in 1998 and was the group leader in the Kusumi Membrane Organizer Project in Nagoya, Japan in 1998-2005 and an assistant professor at Nagoya University in 2000-2005. He joined Purdue University in 2005 as a professor of physics and is the associate head of the department since 2015.


November 30, 2017

Jenny Thomas, University College London

An alternative future for neutrino physics

Abstract: Neutrino Oscillations have provided a new insight into the properties of neutrinos since their discovery almost 20 years ago. There are a number of experiments presently providing new results pointing to a future direction in the field. One fundamental and overarching difficulty associated with any kind of measurements of neutrinos is that they only interact with the weak interaction, making their observation rather rare. This leads to very long wait times for results and the need for larger and larger detectors which eventually break the bank. It is time for a paradigm shift in the way neutrino physics is carried out, without the need for 1000 people for each experiment, sums of money that take your breath away and detectors that are so small they need 20 years to make the next fundamental step. I will give an introduction to the physics, the recent results in the field and then talk about an alternative future where we can make measurements quickly with huge detectors at a fraction of the cost of presently planned experiments.


December 7, 2017

Oleg D. Lavrentovich, Kent State University

Using liquid crystals to command swimming bacteria

Abstract: Self-propelled bacteria are marvels of nature. If we can control their dynamics, we could use it to power dynamic materials and microsystems of the future. Unfortunately, bacterial swimming is mostly random in isotropic liquids such as water and is difficult to control by factors other than transient gradients of nutrients. We propose to command the dynamics of bacteria by replacing water with water-based liquid crystals. The long-range orientational order of the liquid crystal can pre-patterned into various structures by a plasmonic photoalignment technique [1]. The experiments demonstrate that the liquid crystals command the dynamics of bacteria, namely, the trajectories of swimming, polarity of motion, and distribution of bacteria in space [2]. The study of bacteria-liquid crystal system might result in approaches to harness the energy of collective motion for micro-robotic, biomechanical, and sensing devices, as well as micro-mixing and transport of micro-cargo. The work is supported by NSF grants DMR-1507637 and DMS-1729509.

[1] C. Peng, Y. Guo, T. Turiv, M. Jiang, Q.-H. Wei, O.D. Lavrentovich, Patterning of Lyotropic Chromonic Liquid Crystals by Photoalignment with Photonic Metamasks, Advanced Materials 2017, 1606112 (2017).

[2] C. Peng, T. Turiv, Y. Guo, Q.-H. Wei, O.D. Lavrentovich, Command of active matter by topological defects and patterns, Science 354, 882 (2016).

About the speaker: Oleg D. Lavrentovich received his Ph.D. (1984) and Doctor of Science (1990) degrees in Physics and Mathematics from the Ukrainian Academy of Sciences for his research on topological defects in liquid crystals. In 1992 he joined the Liquid Crystal Institute at Kent State University. He served as the director of Institute in 2003-2011. He is currently a Trustees research professor affiliated with the Department of Physics, Chemical Physics Interdisciplinary program and the Liquid Crystal Institute at Kent State. His current research focuses on electro-optics of liquid crystals, topological defects, hybrid colloid-liquid crystal systems, liquid crystals as active matter and liquid crystals as nonlinear electrolytes. He is the editor of Liquid Crystals Reviews (Taylor & Francis), associate editor of Soft Matter (Royal Society of Chemistry), Fellow of APS and SPIE.

Fall 2016

September 8, 2016

Dr. Chris Polly, Fermilab

Muon g-2 and the quest for new physics.

Abstract: One of the most imperative questions in particle physics today is whether or not new physics will emerge at the few TeV scale. Observational hints for new physics have arisen from several sectors with exciting theoretical implications that can potentially be explained by supersymmetry, dark matter, or other exotic models. One of the most persistent hints comes from the Brookhaven muon g-2 experiment, where an ultra-precise measurement of the muon anomalous magnetic moment differs by >3 sigma from the theoretical expectation. The anomalous magnetic moment of the muon provides a unique window into the TeV scale, and a new effort is underway at Fermilab to improve the experimental precision. A review of the physics, the principles behind the experiment, and the incredible journey to bring the experiment to the point it is at today will be discussed.


September 15, 2016

Professor Sambandamurthy Ganapathy, SUNY Buffalo

Nanoscale investigation of strongly correlated oxide materials

Abstract: Strongly correlated materials display a rich variety of phenomena, including superconductivity, giant magnetoresistance, and metal-insulator transitions, as strong interactions lead to competing ground states. Vanadium oxide is a prototypical correlated electron material that exhibits a large metal-insulator transition (MIT) close to room temperature. The scientific interest in this material lies in understanding the fundamental mechanisms that are responsible for driving the transition. The large resistive switching and the convenient MIT temperature make this a potential material in electrical and electro-optic applications as switches and memory elements.

In this talk, I will present results from our studies on the transport properties of single nanobeam devices of vanadium dioxide and epitaxial thin films of nickelates. We seek to control and understand the MIT using several tuning parameters such as temperature, metal doping, and electric field. Probing these materials in the nanoscale and the application of noise spectroscopy allow us to distinguish between possible physical mechanisms that are responsible for the transition and to explore the nonequilibrium physics of correlated materials.


September 22, 2016

Professor Adam Smith, University of Akron

Resolving molecular interfaces in biological membranes

Abstract: The plasma membrane is the boundary between a cell and its surroundings. Protein receptors are embedded in the membrane to create a sensory device that processes environmental cues. The spatial and temporal arrangement of these receptors is critical to function, but the physical and chemical driving forces are not well understood. Membrane protein dimerization, for example, is a key regulator of many receptor pathways, but its role in others is still controversial or completely unknown. Hierarchical assembly of receptor complexes upon ligand stimulation is central to many signaling pathways, but the kinetics and thermodynamics of the assembly process are still poorly understood. Lipids in the membrane play many structural and regulatory roles in receptor activation, but the details of the lipid-protein interface are still largely unexplored because of experimental difficulties. In this seminar, I will describe two ongoing projects in my group. In the first project, we investigate membrane protein interactions in live cells using PIE-FCCS and related methods. These efforts have led to several key insights into the organization and activation mechanism of receptors like plexins, growth factor receptors, and visual photoreceptors. The second project is to resolve the details of lipid-protein coupling in model membranes to build a more complete picture of the chemical landscape that governs cell communication.


September 29, 2016

Professor Peter Lepage, Cornell University

40 Years of Lattice QCD

Abstract: Lattice QCD was invented in 1973-74 by Ken Wilson, who passed away in 2013. This talk will describe the evolution of lattice QCD through the past 40 years with particular emphasis on its first years, and on the past decade, when lattice QCD simulations finally came of age. Thanks to theoretical breakthroughs in the late 1990s and early 2000s, lattice QCD simulations now produce the most accurate theoretical calculations in the history of strong-interaction physics. They play an essential role in high-precision experimental studies of physics within and beyond the Standard Model of Particle Physics. The talk will include a non-technical review of the conceptual ideas behind this revolutionary development in (highly) nonlinear quantum physics, together with a survey of its current impact on theoretical and experimental particle physics, and prospects for the future.


October 6, 2016

Professor Chenggang Tao, Virginia Tech

Interfaces in Atomically Thin 2D Materials.

Abstract: Emerging two-dimensional (2D) materials, such as atomically thin transition metal dichalcogenides and graphene, have been the subject of intense research efforts for their fascinating properties and potential applications in future electronic and optical devices. The interfaces in these 2D materials, including domain boundaries, edges, and heterojunctions, strongly govern the electronic and magnetic behavior and may also potentially host new quantum states. On the other hand, these interfaces are more susceptible to thermal fluctuation and external stimuli. In this talk, I will present our scanning tunneling microscopy (STM) and spectroscopy (STS) explorations of edges of mono- and few-layer molybdenum disulfide (MoS 2 ) nanostructures and will show how step edges on titanium diselenide (TiSe 2 ) surfaces change dynamically due to electrical fields. I will also discuss temperature evolution of novel quasi-1D fullerene nanostructures on graphene.


October 13, 2016

Professor Xiang Qiang (Rosie) Chu, Wayne State University

Protein Dynamics on Multiple Timescales Studied by Neutron Scattering

Abstract: Proteins undergo sophisticated changes in space and time, in order to keep the cells functioning. These motions are believed to ultimately govern the biological function and activities of the protein. Neutron scattering provides exceptional tools for studying the structures and dynamics of protein in real time at the molecular level. In our recent research, we use quasi-elastic neutron scattering (QENS) technique to study the dynamic behavior of a hyperthermophilic protein, IPPase, that is found in the deep-sea, in the time range of 10ps to 1ns. Our results indicate that under a pressure of 100 MPa, close to that of the native environment deep under the sea, IPPase displays much faster relaxation dynamics than a mesophilic model protein, hen egg white lysozyme (HEWL) at all measured temperatures, opposite to what we observed previously under ambient pressure. This contradictory observation provides evidence that the protein energy landscape (EL) is distorted by high pressure, which is significantly different for hyperthermophilic (IPPase) and mesophilic (HEWL) proteins. We further derive from our observations a schematic denaturation phase diagram together with ELs for the two very different proteins, which can be used as a general picture to understand the dynamical properties of thermophilic proteins under pressure. In addition, using a direct time-of-flight Fermi chopper neutron spectrometer (SEQUOIA) at ORNL, we obtained a full map of the milli-eV phonon-like excitations in the fully deuterated protein. The Q range of the observed excitations corresponds to the length scale of about 2.5 to 3 Å, which is close to the length scales of the secondary structures of proteins (4-5 Å) and reflects the collective intra-protein motions. These observations and further investigation using neutron scattering can reveal important macromolecular dynamic behaviors that cannot be otherwise measured by other techniques.


October 27, 2016

Professor Gil Paz, Wayne State University

How Big is the Proton?

Abstract: In 2010 the proton charge radius was extracted for the first time from muonic hydrogen, a bound state of a muon and a proton. The value obtained was five standard deviations away from the regular hydrogen extraction. Taken at face value, this might be an indication of a new force in nature coupling to muons, but not electrons. It also forces to reexamine our understanding of the structure of the proton.

In this talk, I will describe an ongoing research effort that seeks to address and resolve this "proton radius puzzle." In particular, I will discuss: 1) A modern approach to controlling nucleon form factors leading to new model-independent extractions of the proton and neutron magnetic radii. 2) How to separate and control nucleon and nuclear effects in neutrino-nucleus interaction, crucial for the USA and worldwide neutrino program. 3) Reevaluation of proton structure effects in the theory behind the muonic hydrogen result, correcting 40 years of such theoretical calculations. 4) Developing new theoretical tools that would allow to directly connect muonic hydrogen to a new muon-proton scattering experiment.


November 3, 2016

Professor Eva Halkiadakis, Rutgers University

Exploring the Energy Frontier at the Large Hadron Collider

Abstract: The Large Hadron Collider (LHC) at the CERN laboratory is the world's most powerful particle accelerator. The start of the proton collider program at the LHC brought the dawn of the exploration of a new energy frontier. The LHC has had a successful and highly productive Run 1 (2010-2012), colliding protons with a center-of-mass energy up to 8 TeV, and in 2012 the observation of a new Higgs-like boson was announced to the world by the CMS and ATLAS collaborations. The year 2015 marked the beginning of Run 2 of the LHC and we entered a new era of even higher proton collisions at 13 TeV; in 2016 we have broken data-taking records collecting an unprecedented amount of data at these high energies. The LHC experiments have an extensive program of searches for physics beyond the Standard Model, exploring uncharted territory at the energy frontier. I will present the status of the LHC and highlight experimental results using the latest 13 TeV data in Run 2, with a special focus on the CMS experiment.


November 10, 2016

Professor Steffen Bass, Duke University

A data-driven approach to quantifying the shear viscosity of nature's most ideal liquid

Abstract: About a microsecond after the Big Bang, the universe was in a state called the Quark Gluon Plasma (QGP), in which quarks and gluons, the basic constituents of the strong nuclear force, roamed freely. Due to its large expansion, this plasma went through a phase transition to form hadrons - most importantly nucleons - which constitute the building blocks of matter as we know it today. Determining the properties of the QGP would not only teach us about the dynamics of the early universe but also teach us about the properties of its underlying quantum field theory (Quantum Chromo-Dynamics) at high temperatures and densities - domains of the theory that are currently not accessible in first-principles calculations.

Only in the last 10-15 years have accelerators been able to create the conditions of temperature and density in the laboratory that are favorable for the QGP to exist. The Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory was built specifically to observe and study this phase of matter and the Large Hadron Collider (LHC) at CERN has devoted a significant research program to this purpose as well.

One of the most surprising discoveries to come out of QGP research is that it behaves like a liquid with the smallest specific viscosity ever observed in nature. This lecture will elucidate how an interdisciplinary collaboration of experimental and theoretical physicists together with computer scientists and statisticians has been able to tease out the remarkable properties of this extreme liquid and how scientific advances in Bayesian statistics and grid computing have come to bear to advance one of the most dynamic areas of Nuclear Physics.


November 17, 2016

Professor Laura Cadonati, Georgia Tech

The discovery of gravitational waves in Advanced LIGO

Abstract: Gravitational waves, ripples in the fabric of space-time produced by catastrophic astrophysical events, are arguably the most elusive prediction of Einstein's theory of General Relativity, so feeble that Einstein himself thought their detection was impossible. Nevertheless, one hundred years later, the Laser Interferometer Gravitational-wave Observatory (LIGO) has announced the observation of gravitational waves produced by the collision of two black holes. This groundbreaking discovery marks the opening of a new window on the Universe and a new era of gravitational wave astrophysics, where gravitational waves will provide new insights into black holes and neutron stars, and maybe even reveal new objects. In this talk, I will present results from the first observing run of Advanced LIGO, and discuss its implications for a new gravitational wave astronomy.


December 1, 2016

Professor Tobias Baumgart, University of Pennsylvania

Mechanisms of Membrane Curvature Generation

Abstract: Membrane curvature has developed into a forefront of membrane biophysics. Numerous proteins involved in membrane curvature sensing and membrane curvature generation have recently been discovered, including proteins containing the crescent-shaped BAR domain as membrane binding and shaping module. Accordingly, the structure of these proteins and their multimeric complexes is increasingly well-understood. Substantially less understood, however, are the detailed mechanisms of how these proteins interact with membranes in a curvature-dependent manner. New experimental approaches need to be combined with established techniques to be able to fill in these missing details. Here we use model membrane systems in combination with a variety of biophysical techniques to characterize mechanistic aspects of BAR domain protein function. This includes a characterization of membrane curvature sensing and membrane generation. We present a new approach to investigate membrane shape instabilities introduce membrane shape stability diagrams as a powerful tool to enhance the mechanistic understanding of membrane trafficking phenomena, including endocytosis, with molecular detail.


January 19, 2017

Professor Wenjun Zheng, University at Buffalo

Investigating protein dynamics with coarse-grained physics-based modeling

Abstract: Membrane curvature has developed into a forefront of membrane biophysics. Numerous proteins involved in membrane curvature sensing and membrane curvature generation have recently been discovered, including proteins containing the crescent-shaped BAR domain as membrane binding and shaping module. Accordingly, the structure of these proteins and their multimeric complexes are increasingly well-understood. Substantially less understood, however, are the detailed mechanisms of how these proteins interact with membranes in a curvature-dependent manner. New experimental approaches need to be combined with established techniques to be able to fill in these missing details. Here we use model membrane systems in combination with a variety of biophysical techniques to characterize mechanistic aspects of BAR domain protein function. This includes a characterization of membrane curvature sensing and membrane generation. We present a new approach to investigate membrane shape instabilities introduce membrane shape stability diagrams as a powerful tool to enhance the mechanistic understanding of membrane trafficking phenomena, including endocytosis, with molecular detail.


January 26, 2017

Professor Bradford Orr, University of Michigan

Revamping the teaching of Introductory Mechanics

Abstract: Eight years ago the Michigan Physics Department began a process to reinvigorate the teaching of its introductory (freshman) mechanics classes. We had identified a number of issues that were negatively impacting our program and desired a means to address them. This talk will describe the problematic issues and the manner in which they have been addressed. I will discuss specific examples of the introduction of numerical computation in the revamped classes that have excited our faculty and students. One positive outcome is the doubling of majors graduating from our department.


February 2, 2017

Dr. Alex Matos-Abiague, University at Buffalo

Spintronics: Novel Materials and Opportunities

Abstract: Spintronics (or spin electronics), an alternative to conventional electronics recognized by the 2010 Nobel Prize in Physics, is driven by the need for faster, more powerful and yet more efficient devices. Spintronic devices use electron spins, which are ignored in conventional electronics, for nonvolatile information storage, sensing, and logic. While spins are typically manipulated by external magnetic fields, solid-state materials also offer a great potential for spin manipulation using effective, momentum-dependent "magnetic" fields, the so-called spin-orbit fields arising from relativistic effects. Those fields accounting for spin-orbit interactions can be exceptionally large in some materials, leading to exotic topological properties and solid-state realizations of particles predicted in relativistic quantum field theories, such as Weyl, Dirac, and Majorana fermions [1]. This talk will focus on the physical origin of interfacial and synthetic spin-orbit fields [2] as well as their effects on emergent phenomena in hybrid heterostructures, initially studied in high-energy physics. Key implications of spin-orbit-mediated phenomena in topological materials [3], as well as present theoretical challenges and opportunities for novel two-dimensional crystals exhibiting strong spin-orbit coupling, will also be addressed.

1. G. L. Fatin, A. Matos-Abiague, B. Scharf, and I. Žutić, Phys. Rev. Lett. 117, 077002 (2016).
2. T. Hupfauer, A. Matos-Abiague, M. Gmitra, F. Schiller, J. Loher, D. Bougeard, Ch. Back, J. Fabian, and D. Weiss, Nature Comm. 6, 7374 (2015)
3. B. Scharf, A. Matos-Abiague, J. E. Han, E. Hankiewicz, and I. Žutić, Phys. Rev. Lett. 117, 166806 (2016).


February 9, 2017

Professor Sang-Hyun Oh, University of Minnesota

New approaches to nanofabrication for plasmonics and biosensing

Abstract: I will present our recent work based on two unconventional nanofabrication techniques, namely, template stripping for making ultra-smooth patterned metals and atomic layer lithography for mass-producing sub-10 nm gaps. With template stripping, instead of directly patterning noble metal films, which are difficult to plasma-etch, we engineer inverse patterns in crystalline silicon templates using mature IC processing techniques. After metal deposition and peeling, ultra-smooth patterns in the silicon template are faithfully replicated onto a deposited metal film. We have used template stripping to create high-performance plasmonic gratings, waveguides, resonators, nanohole arrays, and ultra-sharp pyramidal tips for various biosensing and spectroscopy applications. I will also present surface modification techniques to combine these metal nanostructures with biomembranes for real-time kinetic biosensing and spectroscopy. Recently our group has demonstrated another technique called atomic layer lithography, which enables wafer-scale production of ultra-long (up to centimeters) and sub-10- nm wide gaps in various metals. The resulting nanogaps have been used for a wide range of optical and electrical experiments, including extraordinary optical transmission through single-digit nanometer gaps, ultralow-power electronic trapping of quantum dots and biomolecules, and surface-enhanced spectroscopies, to name a few. I will present potential applications of this enabling technology in biosensing.


February 16, 2017

Professor Richard Field, University of Florida

Toward an Understanding of Hadron-Hadron Collisions: From Feynman-Field to the LHC

Abstract: In 1973 I received a two-year post-doctoral position in Theoretical Elementary Particle Physics at CALTECH in Pasadena, California. When I arrived at CALTECH I met Richard Feynman and we began a quest to understand the source of the high transverse particles (pions and kaons) that had just been observed at the ISR proton-proton collider at CERN at a center-of-mass energy of W = 53 GeV. Feynman-Field phenomenology resulted in predictions of large transverse momentum particle and "jet" production in hadron-hadron collisions based on the theory of Quantum Chromodynamics (QCD). The goal was to show that QCD was indeed the correct theory of the strong interactions. We constructed the "Field-Feynman" fragmentation model of how the outgoing partons produced hadrons, which for the first time allowed us to simulate, on an event-by-event basis, everything that occurs in a hadron-hadron collision. In 1998 I joined the CDF Experimental Collaboration at Tevatron (W = 1.8 TeV) at Fermilab in Batavia, Illinois. My plan was to produce data that could be used to improve the QCD Monte Carlo models we use to simulate hadron-hadron collisions. Later, as a member of the CMS Experimental Collaboration at the LHC (W = 13 TeV) at CERN in Geneva, Switzerland, I continued this plan. The QCD Monte Carlo models have improved greatly over the years and QCD has become an integral part of the "Standard Model". From 7 GeV pions to 1 TeV jets. It has been a wonderful journey from the "old days" of Feynman-Field collider phenomenology to the Tevatron and the LHC. I would like to share some of this journey with you.


February 21, 2017

Dr. Jian-Huang She, Cornell University

Novel superconductors from quantum paramagnets

Abstract: Superconductivity has been around for more than 100 years. A major challenge still remains as to how to understand strongly correlated superconductors with predictive power. Here we propose a new paradigm for superconductivity building on quantum paramagnets. Such a paradigm enables us to propose a new design pattern, namely a metal/quantum-paramagnet heterostructure, which hosts superconductivity with nontrivial topological properties. Furthermore, we use such a paradigm to provide a unified framework that explains the various puzzling phenomena of a new iron-based superconductor FeSe: its exotic spin dynamics, nematicity without magnetic ordering, and unconventional superconductivity.


February 23, 2017

Professor Carlos Wagner, Argonne National Lab/University of Chicago

Open Questions in Particle Physics

Abstract: Almost a century after the conceptual revolutions brought by the theories of relativity and quantum mechanics, the Standard Model has been established as the correct effective theory describing all physical phenomena in nature, with the exception of gravity. Precision measurements of the recently discovered Higgs boson have provided the first clues on the origin of the mass of all known fundamental particles. As great as these achievements have been, there are several outstanding questions that remain to be answered. In this talk, after reviewing the current status of the field of particle physics, I will describe the efforts directed to answer those questions and to understand the dynamical origin of the ordinary matter as well as the dark matter in the Universe.


March 2, 2017

Dr. Ching-Kit (Chris) Chan, University of California Los Angeles

Driving Dirac and Weyl Materials

Abstract: The discovery of topological materials revolutionized condensed matter physics over the last decade. The topological richness of the electronic band structure brings in many exotic physical properties such as topological robustness, bulk-edge correspondence and quantum anomalies. Collaborative efforts between theorists and experimentalists in this research area have led to remarkable developments from the fundamental understanding of topological phases to material applications. Discovering and manipulating topological matter is one of the most exciting research directions in condensed matter physics nowadays.

These excitements are further elevated by recent progresses in laser-driven topological materials. It is typically difficult to understand physical systems driven far away from equilibrium. However, when a material is driven periodically in time, a well-defined quasi-Hamiltonian exists which permits equilibrium descriptions and fruitful concepts borrowed from solid state physics. The corresponding quasi-energies, known as the Floquet bands, are analogous to Bloch bands in lattice crystals with spatial periodicity. In this Colloquium, I will first review the current experimental situation on the observation of Floquet-Bloch bands by laser-driving 2D Dirac electrons on the surface of a 3D topological insulator. I will then discuss theoretical proposals of driving the 3D generalization---Weyl fermions in semimetal materials. We shall see how the coupling between chiral fermions and chiral photons induces interesting anomalous transport effects and topological phase transitions. I will also present a photogalvanic application of Weyl semimetals for detecting infrared radiations.


March 7, 2017

Dr. Hartwin Peelaers, University of California, Santa Barbara

Fundamental limits on optical transparency of transparent conducting oxides

Abstract: Transparent conducting oxides (TCOs) are a technologically important class of materials with applications ranging from solar cells, displays, smart windows, and touch screens to light-emitting diodes. To enable these applications, TCO materials have to balance two conflicting properties: transparency and conductivity.

The requirement of transparency is typically tied to the band gap of the material being sufficiently large to prevent absorption of visible photons. This is a necessary but not sufficient condition: indeed, the high concentration of free carriers, required for conductivity, can also lead to optical absorption by excitations of electrons to higher conduction-band states. In TCOs these direct transitions to higher conduction band states require an amount of energy larger than that of visible light photons. However, light absorption can still occur due to indirect free-carrier absorption, and a good understanding of these indirect processes is important to improve current materials and applications.

In this talk, I will use insights obtained by accurate, parameter-free calculations based on density functional theory to discuss the physics of the processes limiting the transparency, and will compare quantitative results for two widely used TCO materials.


March 9, 2017

Dr. Ran Cheng, Carnegie Mellon University

Magnetic Nanostructures: A Playground for Fundamental Physics

Abstract: Nature becomes amazingly different from what we perceive with our eyes when zoomed in to the nanometer scale, where atomic spins interact and form diverse magnetic configurations. Besides holding great technological promise, magnetic nanostructures have also enabled a vibrant playground for fundamental physicsa thriving field known as spintronics. In this talk, I will introduce selected recent progress in spintronics that has reshaped our understanding of transport phenomena occurring at the microscopic scale. Special attention will be paid to antiferromagnetic materials, which is remarkably rich in nature, though its significance has been overshadowed by ferromagnets. Taking the interplay between electronic, magnetic, and mechanical degrees of freedom as a common thread, I will guide us into various intriguing phenomena involving domain wall motion, spin-Hall oscillator, spin-wave Faraday rotation, spin Nernst effect, and emergent gravity. In addition, I will demonstrate a conceptual advance that helps us understand many unique features of magnetic systems known as the Berry phase effect, the importance of which has been recognized by the 2016 Nobel prize in physics.


March 23, 2017

Professor Sergei Voloshin, Wayne State University

Most vortical fluid globally polarized Quark-Gluon Plasma

Abstract: Ultrarelativistic nuclear collisions provide a unique possibility to study the matter at extreme conditions not available in any other laboratory settings. These include highest temperature and energy density, strongest electromagnetic fields, lowest viscosity over entropy density (ideal liquid) and, what is the main theme of this presentation, the highest vorticity, originating in the large angular momentum of the system. I will present the recent developments in the understanding of the role of vorticity in high energy nuclear collision dynamics, as well as latest experimental measurements of the global polarizations - the particle spin alignment with the system orbital momentum. The relation of the global polarization effect to Barnett and Einstein-de Haas effects, as well as to chiral anomalous effects, both in nuclear collisions and condensed matter, will be also briefly discussed.


Professor Adam Riess, Johns Hopkins University, Nobel Prize in Physics (2011)

Supernovae and the Discovery of the Accelerating Universe

Abstract: In 1929 Edwin Hubble discovered that our Universe is expanding. Eighty years later, the Space Telescope which bears his name is being used to study an even more surprising phenomenon, that the expansion is speeding up. The origin of this effect is not known but is broadly attributed to a type of "dark energy" first posited to exist by Albert Einstein and now dominating the mass-energy budget of the Universe. I will describe how our team discovered the acceleration of the Universe and why understanding the nature of dark energy presents one of the greatest remaining challenges in astrophysics and cosmology.


April 13, 2017

Professor Stacy McGaugh, Case Western Reserve University

The Radial Acceleration Relation in Rotationally Supported Galaxies

Abstract: 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.

Winter 2016

January 21, 2016

Professor Emily Liu, Rensselaer Polytechnic Institute

Measuring Sustainability in Advanced Energy Systems through Exergy, Exergoeconomic, Life Cycle, and Economic Analyses

Abstract: The Encyclopedia of Life Support Systems defines sustainability or industrial ecology as "the wise use of resources through critical attention to policy, social, economic, technological, and ecological management of natural and human-engineered capital so as to promote innovations that assure a higher degree of human needs fulfilment, or life support, across all regions of the world, while at the same time ensuring intergenerational equity" (Encyclopedia of Life Support Systems 1998). Developing and integrating sustainable energy systems to meet growing energy demands is a daunting task. Although the technology to utilize renewable energies is well understood, there are limited locations which are ideally suited for renewable energy development. Even in areas with significant wind or solar availability, backup or redundant energy supplies are still required during periods of low renewable generation. This is precisely why it would be difficult to make the switch directly from fossil fuel to renewable energy generation. A transition period in which a base-load generation supports renewables is required, and nuclear energy suits this need well with its limited life cycle emissions and fuel price stability.

Sustainability is achieved by balancing environmental, economic, and social considerations, such that energy is produced without detriment to future generations through loss of resources, harm to the environment, etcetera. In essence, the goal is to provide future generations with the same opportunities to produce energy that the current generation has. This research explores sustainability metrics as they apply to a small modular reactor (SMR)-hydrogen production plant coupled with wind energy and storage technologies, so-called nuclear hybrid energy system (NHES), to develop a new quantitative sustainability metric, the Sustainability Efficiency Factor (SEF), for comparison of energy systems.


January 28, 2016

Professor Peter Hoffmann, Wayne State University

Why physicists should care about biology

Abstract: In 1949, Max Delbrück observed that the goal of physics in biology should be "to grasp more clearly how the same matter, which in physics displays orderly and relatively simple properties, arranges itself in the most astounding fashions as soon as it is drawn into the orbit of the living organism. The closer one looks at these performances of matter in living organisms the more impressive the show becomes. The meanest living cell becomes a magic puzzle box full of elaborate and changing molecules." How far has physics evolved in understanding this "magic puzzle box" that is life? For many physicists, biology seems like "stamp-collecting" in the words sometimes attributed to Rutherford. Indeed, for the uninitiated, the complexity of molecular biology and the resulting strange terminology can be overwhelming and seemingly lacking a coherent structure. However, this would be a false conclusion: In reality, since the molecular biophysics revolution, which was originated in large part by physicists such as Delbrück and Crick, we now have a coherent, but still, incomplete framework to understand biological systems. This framework includes crucial perspectives from statistical and molecular physics, but also from evolution, chemistry, engineering, and computer science. Understanding how life works continues to be one of the grandest challenges of science. For the physicist, it is endlessly fascinating trying to understand how in living systems noise creates order, physics interact with information, and complexity emerges at multiple levels. In this colloquium, I will attempt to give a primer of biology for physicists and try to evoke the sense of wonder that keeps biophysicists chasing the mysteries of life.


February 4, 2016

Professor Qiong Yang, University of Michigan - Ann Arbor

From molecules to development: revealing design principles of biological clocks

Abstract: Organisms from cyanobacteria through vertebrates make use of biochemical and genetic oscillators to drive repetitive processes like cell cycle progression and vertebrate somitogenesis. Despite the complexity and diversity of these oscillators, their core design is thought to be shared. Notably, most of them contain a core positive-plus-negative feedback architecture. Here I start with Xenopus early embryonic mitotic cycles as a motivating example and discuss how the positive feedback functions as a bistable switch and the negative feedback as a time-delayed, digital switch (Yang and Ferrell, Nat Cell Biol, 2013; Ferrell, Tsai, and Yang, Cell, 2011). I will also discuss our ongoing projects. We search network topologies to identify potential motifs for essential clock functions, such as robustness and tunability. In addition, we employ mathematical modeling, microfluidic techniques, and optical imaging as an integral approach to understand the design and coupling of multiple clocks in early zebrafish embryos.


February 11, 2016

Professor Xianglin Ke, Michigan State University

Tuning quantum properties in correlated ruthenates

Abstract: Transition-metal oxides display a large variety of exotic electronic and magnetic properties, such as high-Tc superconductivity, colossal magnetoresistance, multiferroicity, metal-insulator transitions, etc. These remarkable phenomena arise from the electron correlation and the strong interplay between spin, charge, lattice and orbital degrees of freedom. The resultant competition of various types of energetic states makes such materials dramatically susceptible to external parameters, leading to rich and complex phase diagrams. In this talk, I shall use a bilayer ruthenate, Ca3Ru2O7, as an example to discuss the emergent phenomena achieved by systematically tuning materials magnetic and electronic properties via chemical doping, magnetic field, and pressure. I shall show that this system provides a rare opportunity to investigate the interplay between correlated metal and Mott insulator.


February 18, 2016

Professor Maikel Rheinstadter, McMaster University

Frontiers in Membrane Biophysics

Abstract: One of the major challenges of modern physics is to contribute to biology and life sciences. Neutron and X-ray beams are prime tools to study molecular structure and dynamics in membranes in-situ, under physiological conditions [1].

The experiments give access to nanoscale diffusion processes within and across the membranes, effects of macromolecules on membrane properties, such as ethanol and cholesterol, the interaction with common drugs, such as aspirin, ibuprofen and cortisone, and their side effects, detection and characterization of membrane raft structures and protein-protein interactions in Alzheimer's disease. The quantitative measurements lend themselves for comparison with computer simulations. I will talk about current topics in membrane biophysics, the associated experimental challenges and present exciting recent results and potential biomedical applications.

View references


February 25, 2016

Professor Alexei Stuchebrukhov, UC Davis

Electron transport and energy generation in biological cells

Abstract: Quantum transport via long-distance electron tunneling is at the basis of biological energy generation machinery in living cells. Electron transport coupled to proton translocation across the membranes gives rise to proton gradient that drives the synthesis of ATP. In this seminar, I will discuss the principles and mechanisms of redox-driven proton pumps - the enzymes that create proton gradient and utilize quantum tunneling for their function.


March 3, 2016

Professor Richard Lebed, Arizona State University

The XYZ Affair: A Tale of the Third (and Fourth) Hadrons

Abstract: In the past 13 years, many new particles have been discovered that are clearly hadrons (interacting via the strong nuclear force), but do not seem to fit into either of the known hadron categories of meson (quark-antiquark) or baryon (3 quarks). Several species of these "exotic" particles, called X, Y, and Z, are now believed to be tetraquarks, and last July the LHC announced the discovery of pentaquark states, P_c. We begin by reviewing the basics of QCD (quarks, color, confinement, etc.), and then turn to the question of how conventional mesons are identified, which allows one to identify exotics. After reviewing their experimental discovery, we consider the question of how exotics are assembled. Several competing physical pictures attempt to describe the structure of exotics: as molecules of known hadrons, as the result of kinematical effects, and others. I propose that they arise due to the formation of compact diquarks, a well-known but under-appreciated phenomenon of QCD. The competing facts of kinematics and diquark confinement create an entirely new kind of bound state: not a molecule with well-defined orbits, but an extended object that lasts only as long as it takes for quantum mechanics to allow the separated quarks and antiquarks to "find" one another, and allow decays to occur. I will discuss several observed effects that support this picture.


March 10, 2016

Professor W.J. Llope, Wayne State University

If you can't stand the hot (stones), get out of the kitchen!

Abstract: Ionizing radiation, the subatomic particles with energies large enough to cause genetic mutations and potentially cancer, surrounds us. It rains on us from above, is in our food, rises into the air from the ground under our homes, and is key to many beneficial medical diagnostic and therapeutic procedures. Physicists, like myself, that smash nuclei together at high speeds are aware of, and comfortable with, an additional exposure beyond this natural background resulting from our research. One day a few years ago, I was asked to appear in a local TV news piece investigating a homeowner's claim that his granite kitchen countertops had killed his dogs and was thus assumed to be greatly endangering his family. This propelled me into few year hobbies to understand the physics of radiation from granite countertops. Along the way, I ran into (unnecessarily) angry granite retailers, a public already overly worried about radiation risks, local and national media coverage, and several forms of subtle industrial subterfuge. At the same time, I collected a wide variety of samples of granite countertops available for sale to homeowners from random granite dealers, and then measured the radiation rates and activity concentrations of the major radioactive sources, 40-K, U-nat, and 232-Th, using a "full spectrum analysis". An anthropomorphic phantom and the "geant4" physics simulation package was used to relate the measured activity concentrations to the potential yearly direct-radiation doses to kitchen occupants. The results were published [1]. In this talk, I will share with you some of the things I learned from this hobby.

[1] W.J. Llope, "Activity concentrations and dose rates from decorative granite countertops", Journal of Environmental Radioactivity, Volume 102, Issue 6, June 2011, Pages 620-629, ISSN 0265-931X,


March 24, 2016

Professor Casey W. Miller, Rochester Institute of Technology

Admissions Criteria and Diversity in STEM Graduate Programs

Abstract: The National Academies have suggested that increasing diversity in Science, Technology, Engineering, and Math will be critical to the future competitiveness of the US in these areas [1], and both the National Science Foundation [2] and the American Physical Society [3] are taking this seriously. In this talk, I will discuss several opportunities that may help move toward meeting this goal, and, importantly, the potential benefits to programs and individual investigators willing to take on these challenges. The most universally applicable and implementable actions regard perturbing graduate admissions policies and practices [4, 5], and employing key features of successful Bridge Programs into graduate programs [6]. Despite the prevalent use of minimum acceptable scores by admissions committees, there is no correlation between GRE scores and research ability. I will remind the community that the use of minimum acceptable GRE scores for admissions is in opposition to ETS's Guide to the Use of GRE Scores, and I will present data showing that this practice will have (has had?) a negative impact on diversity in graduate programs. I will conclude by discussing non-cognitive competencies and their role in student selection processes [7].

  1. National Academy of Sciences, National Academy of Engineering, and Institute of Medicine, "Expanding Underrepresented Minority Participation: America's Science and Technology Talent at the Crossroads," The National Academies Press (2011);
  2. Joan Ferrini-Mundy, "Driven by Diversity," Science 340, 278 (2013).
  4. Casey W. Miller, "Admissions Criteria and Diversity in Graduate School,"APS News, The Back Page, February 2013.
  5. Casey W. Miller and K. G. Stassun, Nature 510, 303-304 (11 June 2014) | doi:10.1038/nj7504-303a
  6. Stassun, K.G., Sturm, S., Holley-Bockelmann, K., Burger, A., Ernst, D., & Webb, D., "The Fisk-Vanderbilt Masters-to-PhD Bridge Program: Broadening Participating of Underrepresented Minorities in the Physical Sciences. Recognizing, enlisting, and cultivating 'unrealized or unrecognized potential' in students", American Journal of Physics 79, 374 (2011).
  7. Casey W. Miller, "Using Non-Cognitive Assessments in Graduate Admissions to Select Better Students and Increase Diversity", STATUS, p1, January (2015)


March 31, 2016

Professor Michael Cushing, University of Toledo

Hunting for Cool Brown Dwarfs with WISE

Abstract: Brown dwarfs are stellar-like objects whose central temperatures are not high enough to fuse hydrogen into helium (the defining property of a star). The study of cool brown dwarfs with surface temperatures less than 500 K can offer important insights into the complex physics of ultracool atmospheres, the shape of the initial mass function, and the low-mass limit of star formation. We have been using the Wide-field Infrared Survey Explorer (WISE) to search for just such a population of brown dwarfs and have identified twenty cool browns dwarfs that populate a new spectral class, dubbed 'Y'. In this talk, I will present the discovery of the Y dwarfs, summarize our current understanding of their physical properties, and discuss the enigmatic spectral energy distribution of the archetype Y dwarf WISE 1828+2650.


April 7, 2016: Vaden Miles Lecture

Professor H. Eugene Stanley, Boston University

Economic fluctuations and statistical physics

Abstract: Recent analysis of truly huge quantities of empirical data suggests that classic economic theories not only fail for a few outliers but that there occur similar outliers of every possible size. In fact, if one analyzes only a small dataset (say one million data points), then outliers appear to occur as "rare events". However, when we analyze orders of magnitude more data (200 million data points!), we find orders of magnitude more outliers---so ignoring them is not a responsible option, and studying their properties becomes a realistic goal. We find that the statistical properties of these "outliers'' are identical to the statistical properties of everyday fluctuations. We report a recent discovery that the same laws govern the formation and bursting of large bubbles as tiny bubbles, over a factor of 1,000,000,000 in timescale.

Financial market fluctuations are characterized by many abrupt switchings on very short timescales from increasing "microtrends" to decreasing "microtrends" -- and vice versa. We show that these switching processes have quantifiable features analogous to those present in phase transitions, and find the striking scale-free behavior of the time intervals between transactions both before and after the switching occurs. We interpret our findings as being consistent with time-dependent collective behavior of financial market participants. We test the possible universality of our result by performing a parallel analysis of volatility and transaction volume fluctuations.

This work was carried out in collaboration with a number of colleagues, chief among whom are T. Preis, J. J. Schneider, X. Gabaix, V. Plerou, and P. Gopikrishnan.


April 14, 2016

Professor Thomas Blum, University of Connecticut

The muon anomalous magnetic moment and the search for new physics

Abstract: The muon's anomalous magnetic moment, or g-2, was measured to fantastic accuracy at BNL's E821 experiment, 0.54 ppm. It has been computed in our most fundamental theory, the Standard Model of particle physics, to slightly better accuracy, and the two differ by a tantalizing three standard deviations. To understand if this signals new physics, experimentalists are set to improve the accuracy of the measurement by a factor of four at FNAL's E989 experiment, beginning in 2017. Meanwhile, theorists are hard at work reducing theory errors, mainly from the difficult hadronic contributions arising from the fundamental theory of the interactions of quarks and gluons, Quantum Chromodynamics (QCD). I will discuss all of this with an eye towards the latter and our first principle calculations using lattice QCD.

Fall 2015

September 10, 2015

Professor Peter F. Green, University of Michigan - Ann Arbor

Nanoscale Phenomena in Macromolecular Materials

Abstract: Molecular design strategies have enabled the synthesis of polymers for diverse applications that include: coatings, lubrication, organic solar cells, light emitting diodes, actuation and drug delivery. A notable scientific challenge is associated with the fact that many of these applications require polymer thin films with thicknesses in the range of nanometers, or tens of nanometers. In this thickness range the physical properties of polymers are known to deviate from the bulk in part due to entropic and enthalpic interactions between these large macromolecules and external interfaces. Subtle deviations of the local structure in relation to the bulk, due to such interactions, are often manifested in film thickness dependent properties in the nanoscale thickness range. Macromolecules of differing architectures (linear chain or branched), but otherwise of identical chemical structure, have recently been shown to exhibit vastly different behaviors. The fundamental origins of the nanoscale thickness dependent phenomena in polymers will be discussed. Most of the presentation will be devoted to a discussion of wetting, aging and glass transition phenomena.


September 17, 2015

Professor Takeshi Egami, University of Tennessee - Knoxville and Oak Ridge National Laboratory

Liquid-State-Physics: From Superfluid 4He to Metallic Glass

Abstract: Liquids are found everywhere. 70% of the earth is covered by ocean. Our body is mostly made of water. And yet we understand so little about the liquid at the atomic level. This is because most of the theoretical and experimental tools in condensed matter physics assume lattice periodicity and translational invariance, whereas in the liquid atoms are constantly moving and are arranged in a seemingly chaotic manner. Fortunately, advances in experimental methods and computational power are making it easier to develop a better understanding of the liquid state. For instance by using a novel method of dynamic pair-density function (DPDF) analysis using inelastic neutron scattering we found that in superfluid 4He the local structure of Bose-Einstein condensate is different from the normal state due to the Pauli exclusion principle [1]. Through computer simulation, we found that in high-temperature metallic liquids the elementary excitations are local topological excitations in the atomic connectivity network, rather than phonons, and they determine viscosity [2]. The glass transition and mechanical behavior of metallic glasses are also governed by local topological changes in the atomic connectivity network [3,4]. These findings hopefully would seed the growth of a new discipline of "liquid-state-physics".

[1] W. Dmowski, S.-O. Diallo, K. Lokshin, G. Ehlers and T. Egami, unpublished.
[2] T. Iwashita, D. M. Nicholson and T. Egami, Phys. Rev. Lett., 110, 205504 (2013).
[3] Y. Fan, T. Iwashita and T. Egami, Nature Communications, 5, 5083 (2014).
[4] T. Egami, Mod. Phys. Lett. B, 28, 1430006 (2014).


September 24, 2015

Professor Li Yang, Washington University - St. Louis

Black Phosphorus and Beyond

Abstract: We present our theoretical studies of the unusual electric, optical, thermal, and piezoelectric properties of a new family of two-dimensional (2D) materials, black phosphorus and its corresponding group IV-VI isoelectronic materials. Using advanced GW-Bethe-Salpeter equation (BSE) calculations, we incorporate electron-electron and electron-hole interactions which are prominent in 2D materials, and predict the enlarged quasiparticle band gap and enhanced excitonic effects. We also predict several unique properties of few-layer black phosphorus. (1) The in-plane anisotropic electrical conductance is rotated by 90 degrees under a moderate strain. (2) The exciton-dominated optical absorption spectra are highly anisotropic with respect to the polarization of the incident light. (3) The lattice thermal conductance is also anisotropic, making black phosphorus very promising for thermoelectric applications. (4) We predict the formation of Dirac cones in compressed black phosphorus, giving rise to novel graphene-like electronics and topological semimetals. Most of these predictions have been confirmed by subsequent experiments.
Beyond black phosphorus, we find that the corresponding group IV-VI isoelectronic materials may exhibit dramatically enhanced piezoelectric effects. Using the modern theory of polarization, we find that the characteristic piezoelectric coefficients of monolayer GeS, GeSe, SnS, and SnSe are about two orders of magnitude larger than those of known transition metal dichalcogenides (TMDCs) and bulk piezoelectric materials. This "giant" piezoelectricity may open the door for energy production and sensors in wearable and transparent devices.


October 1, 2015

Professor Jeremy Bassis, University of Michigan - Ann Arbor

The role of ocean warming in driving ice sheet disintegration

Abstract: Ice is unusual. Not only does it exist naturally in all three phases (vapor, solid and liquid) on the surface of the Earth, it also remains brittle up to the melting point. A consequence of this behavior is that relatively small changes in the Earth's global energy budget leads to large swings in the amount of ice covering the surface of our planet. For example, we have known for nearly a century that ice sheets wax and wane and these glacial cycles are driven by millennial (and longer) changes in atmospheric temperature. However, evidence increasingly also shows that glacial cycles are punctuated by abrupt, rapid disintegration of vast portions of ice sheets. These disintegration events can be extremely rapid with some of the largest events involving near-total disintegration of large sections of an ice sheet in as little as a few centuries. Surprisingly, these disintegration events show little correlation with atmospheric temperature; many events initiating during periods when atmospheric temperatures were extremely cold. Similarly, more recent observations over the past decade show the widespread retreat of glaciers and ice sheets, but only weak and occasionally negative correlations between glacier behavior and atmospheric temperature variations. Here we use models and observations over the past decade to show that many of these anomalous retreat events are in fact triggered by relatively modest amounts of subsurface ocean warming hundreds of meters beneath the surface of the ocean. We show that because glaciers evolve towards a critical point, small perturbations can trigger an unstable brittle failure of ice, leading to rapid retreat.

Moreover, because glaciers in contact with the ocean are always near the pressure melting point, relatively small changes in ocean heat transport can trigger large changes. Despite large uncertainties in ocean forcing, we show that this feedback mechanism can explain many of the most dramatic glacier changes observed over the past several decades and is consistent with millennial-scale ice sheet changes previously inferred. If this theory is confirmed by future observations, it implies that sea level rise in the coming centuries could be much larger than models are currently predicting.


October 8, 2015

Professor Edward Cackett, Wayne State University

X-ray reverberation mapping of supermassive black holes

Abstract: Reverberation mapping is a technique making use of echoes of light in order to determine the size, geometry and kinematics of objects that would be otherwise spatially unresolvable. It has been widely used for 30 years in optical astronomy to probe gas moving at thousands of km/s a few light days from supermassive black holes at the centers of galaxies. However, the recent discovery of X-ray reverberation has opened up a new path to probing the most extreme, innermost regions around supermassive black holes. Time lags due to light travel time between the reflected and direct X-ray emission components are of the order of a few tens of seconds, corresponding to a size scale of the order of just a few gravitational radii. Hence, X-ray reverberation looks at gas on the verge of passing the black hole event horizon. Since the initial discovery in 2009, over a dozen more lags have now been seen, with the size of the lag scaling with black hole mass. While the initial discoveries involved time lags between two continuum bands, an exciting development has been the detections of lags between the direct continuum and the broad Fe Kalpha emission line, which has been seen in a handful of objects. Here, I will present a look at X-ray reverberation lags and the implications and prospects for probing the geometry of the inner emitting region around supermassive black holes.


October 15, 2015

Professor Michael Rubinstein, University of North Carolina at Chapel Hill

Airway Surface Brush Sweeps Lungs Clean: Polymer Physics Helps Us Breathe Easier

Abstract: The classical view of the airway surface liquid (ASL) is that it consists of two layers mucus and periciliary layer (PCL). Mucus layer is propelled by cilia and rides on the top of PCL, which is assumed to be a low viscosity dilute liquid. This model of ASL does not explain what stabilizes the mucus layer and prevents it from penetrating the PCL. I propose a different model of ASL in which PCL consists of a dense brush of mucins attached to cilia. This brush stabilizes mucus layer and prevents it penetration into PCL, while providing lubrication and elastic coupling between beating cilia. Both physical and biological implications of the new model will be discussed.


October 29, 2015

Professor Brian Saam, University of Utah

Hyperfine Physics in Alkali-Metal Vapors

Abstract: Although alkali-metals were all discovered before the end of the 19th century, vapors of these Column I elements have been studied with particular intensity in the last 75 years, first as pseudo-one-electron systems with easily accessed optical or near-infrared Pâ†'S transitions to the ground state having strong oscillator strengths. Currently, they are widely used in precision magnetometry, atomic clocks, and in gyroscopes; they are also of fundamental importance in the study of cold atoms, Bose-Einstein condensates, and atom interferometry even some table-top searches for physics beyond the standard model. All stable alkali-metal isotopes have half-integer nuclear spin, and the ground-state hyperfine coupling to the valence electron generates a rich spin physics that is crucial to all of these areas of study. Our laboratory focuses on optical pumping: the use of circularly polarized resonance light to produce large non-equilibrium ground-state spin polarization in alkali-metal vapors. We also work on the technique of spin-exchange transfer of this polarization to the nuclei of certain noble gases (3He and 129Xe), which finds application to magnetic resonance imaging of the lung. We have worked most recently on characterizing magnetic-resonance frequency shifts in hyperfine transitions that result from interactions between the polarized alkali-metal vapor and the polarized noble-gas nuclei. These are studied optically with much higher sensitivity than inductive techniques; indeed, such shifts can be used as a sensitive probe of the noble-gas magnetization.


November 5, 2015

Professor Joern Putschke, Wayne State University

Probing the Quark-Gluon-Plasma with Jets

Abstract: At extremely high temperatures (trillions of Kelvin), our theory of the nuclear force predicts that quarks and gluons are deconfined in a state of matter called the Quark-Gluon Plasma (QGP). Extensive measurements at the Relativistic Heavy Ion Collider (RHIC) and Large Hadronic Collider (LHC) revealed that the QGP exhibits very remarkable properties, such as behaving as a nearly "perfect liquid". One of the fundamental questions is to understand how a nearly perfect liquid arises from matter which, at short distance scales, is made of weakly interacting quarks and gluons. One approach to answering this question is to utilize jets as "microscopes", since their modification (jet quenching) as they travel through the QGP is influenced by the structure of the medium at many length scales. I will discuss the latest experimental results while emphasizing the Wayne State contributions, in particular on the complementarity of RHIC and LHC measurements, which is critical to relate observed modifications of jets to the inner workings of the QGP. Future directions and experimental opportunities, in particular at RHIC, in this vibrant field of research, will be discussed as well.


November 12, 2015

Professor Pai-Yen Chen, Wayne State University

Nanoantennas, Metasurfaces and Metamaterials: Novel Architecture to Tailor and Enhance Light-Matter Interactions

Abstract: Plasmonic nanostructures and metamaterials offer unprecedented opportunities to tailor and enhance the interaction of waves with materials. In my talk, I will describe our recent progress and research in these research areas, showing how tailored nanostructures and suitable arrangements of them into (1-D) nanoantennas, (2-D) metasurfaces, and (3-D) metamaterials may open exciting venues to manipulate and control light at nanoscale dimensions.

I will discuss our most recent theoretical and experimental findings, including plasmonic devices to control, localize and emit light, giant nonlinearities and quantum optical effects in properly tailored nanoantennas and metasurfaces, and new avenues for harvesting and conversion of emissive energy using metamaterials. Physical insights into these exotic phenomena, new devices based on these concepts, and their impact on technology will be discussed during the talk.


December 3, 2015

Professor Michael Lisa, Ohio State University

The Physics of Sports: A real science course for the non-science major

Abstract: Ohio State University offers a one-semester course on the Physics of Sports, which satisfies a GEC science requirement of all students. Scholarship athletes, business and liberal arts majors make up the majority of the ~80 students enrolled in the class, though interested sports enthusiasts from more technical fields join as well.

The class is far from the "Physics for Poets" type of course that some expected, leading to some initial math- and science-anxiety. It is gratifying when some of this anxiety is replaced by a self-confidence in many students that they can, indeed, handle and appreciate a "real" mathematical science course on material they already enjoy.

While the underlying physics lies of course squarely in the realm of classical mechanics, and familiar topics must be covered, the course aims to be unique not simply a standard classical mechanics class with sports examples.

I will share some specific lessons learned and insights gained while developing and implementing this course over the past five years. This talk does not present formal physics education research.


December 10, 2015

Professor Ka Yee Lee, University of Chicago

Beyond Wrinkling: Stress Relaxation in Lung Surfactant Monolayers and Other Thin Films

Abstract: Surfactants at air/water interfaces are often subjected to mechanical stresses as the interfaces they occupy are reduced in area. For lung surfactants during exhalation, the monolayer collapse manifests itself as protrusions of folds into the subphase. These folds remain attached to the monolayer and reversibly reincorporated upon expansion (inhalation). This folding transition in monolayers is not limited to lung surfactant films, but rather represents a much more general type of stress relaxation mechanism. Collapse modes are found most closely linked to in-plane rigidity. We characterize the rigidity of the monolayer by analyzing in-plane morphology on numerous length scales. More rigid monolayers collapse out-of-plane via a hard elastic mode similar to an elastic membrane, with the folded state being the final collapse state, while softer monolayers relax in-plane by shearing. For the hard elastic mode of collapse, we have further demonstrated experimentally and theoretically that the folded state is preceded by a wrinkled state, and similar wrinkle to fold transitions has been observed in elastic thin films ranging from 2 nm to 10 μm in thickness of completely different chemical nature (lung surfactant lipid monolayers, gold nanoparticle trilayers, and polyester sheets).

Winter 2015

January 22, 2015

Myriam Sarachik, City College of New York

Critical Behavior of Strongly-Interacting 2D Electron System

Abstract: Two-dimensional (2D) electron systems obey Fermi liquid theory at high electron densities and are expected to undergo one or more transitions to spatially and/or spin-ordered phases as the density is decreased, ultimately forming a Wigner crystal in the dilute, strongly interacting limit. Unexpected behavior has been observed as the electron density is decreased and the electron interactions become important relative to their kinetic energy. Most interestingly, a metal-insulator transition has been claimed based on the observation that the resistivity changes abruptly from metallic to insulating behavior with decreasing electron density. This claim is supported by a detailed analysis of the magnetoresistance that suggests that the electrons' effective mass diverges. However, many have questioned whether these observations signal the occurrence of a true phase transition or whether they are due to a crossover. Following a brief review of background material, I will report new measurements [1] that show that with decreasing electron density ns, the thermopower of a low-disorder 2D electron system in silicon exhibits a sharp increase by more than an order of magnitude, tending to a divergence at a finite, disorder-independent density nt. Unlike the resistivity which may not clearly distinguish between a transition and crossover behavior, the thermopower provides clear evidence that an interaction-driven phase transition occurs with decreasing density to a new low-density phase which may be a precursor phase, or a direct transition to the long sought-after Wigner solid.

[1] A. Mokashi, S. Li, B. Wen, S. V. Kravchenko, A. A. Shashkin and V. T. Dolgopolov, and M. P. Sarachik, Phys. Rev. Lett. 109, 096405 (2012)


January 29, 2015

Gordy Kane, University of Michigan - Ann Arbor

String Theory and Our Real World

Abstract: String theory is exciting not only as a quantum theory of gravity, but also because it can address most or all of the questions we hope to understand about the physical world, about the quarks and leptons that make up our world, the forces that act on quarks and electrons to form our world, cosmology, and much more. I'll explain why string theory is testable in basically the same ways as the rest of physics, why many people including string theorists are confused about that, and how string theory is already or soon being tested in several ways, including LHC physics and Higgs boson physics.


February 5, 2015

Eric Bell, University of Michigan - Ann Arbor

The outskirts of Milky-Way mass galaxies - a probe of dark matter driven growth

Abstract: Dark matter is central to our idea of how galaxies grow and develop. Dark matter overdensities trigger the initial collapse, dark matter halos merge and grow continuously to the present day, and dark matter constitutes most of the gravitationally important mass in present-day galaxies. Yet, we know precious little about the actual dark matter merger and assembly history of galaxies, and do not understand well how it correlates with the observable properties of galaxies. I will argue that the outskirts of galaxies (their stellar halos) are ideal environments to learn about the growth history of galaxies' dark matter halos and how that growth affects the visible parts of galaxies. I will show that the outskirts of the Milky Way reflect its cosmological growth history, and I will argue that most of its outskirts are formed from the debris of tidally-shredded dwarf galaxies, with some contribution in the inner parts from kicked-up disk. I will discuss our new measurements of the outskirts of a number of nearby galaxies, focusing on the diversity in their properties, reflecting on what that might tell us about how galaxies grow in a dark matter dominated universe.


February 19, 2015

John Arrington, Argonne National Lab

Clusters, Correlations and Quarks: a High-Energy Perspective on Nuclei

Abstract: Nuclei form the core of matter, but a description in terms of their fundamental constituents - quarks and gluons - remains elusive. Effective models of nuclei exist for use in different applications: a static nucleus defined simply by its mass and charge distribution in atomic physics, a Fermi gas model of quasi-free nucleons for moderate-energy lepton-nucleus scattering, or a simple bag of quarks for high energy collisions. Recent results suggest that dense structures in nuclei impact measurements across all of these energy scales, from neV atomic transitions to TeV probes sensitive to the parton distributions. I will present data from Jefferson Lab experiments which use multi-GeV electrons to isolate and study extremely dense and energetic components of nuclear structure. A connection between these dense two-nucleon correlations and the EMC effect in nuclei suggests that two-body effects may drive a significant part of the modification of nucleon structure in dense nuclei. I will summarize planned measurements aimed at understanding this link and future possibilities which would require a future Electron-Ion Collider.


February 26, 2015

Jenny Greene, Princeton University

MASSIVE Galaxies and Small Supermassive Black Holes


I will discuss MASSIVE, an ambitious new integral-field survey of the ~100 most massive galaxies within 100 Mpc. Using integral-field spectroscopy covering 200 pc to 20 kpc scales, we are studying the assembly history of massive galaxies from the supermassive black holes at the center to the dark matter halos on large scales. I will then discuss black hole scaling relations over a large range in galaxy mass, using MASSIVE observations at the high end and megamaser disk galaxies at low mass.


March 12, 2015

Michael Shvartsman, University of St. Thomas

Tornado: Fractal Powers in Swirling Vortex Solutions

Abstract: We will discuss some aspects of tornado mechanics including the touchdown stage that is often associated with
rotating fluid in contact with the ground. In many cases such flow can be regarded as axisymmetric although it came under some criticism in recent years. We consider a modification of the fluid flow model for a tornado-like swirling vortex developed by J. Serrin in 1972, where velocity decreases as the reciprocal of the distance from the vortex axis. Recent studies, based on radar data, indicate that the angular momentum in a tornado may not be constant with the radius, and thus suggest a different scaling of the velocity field with respect to vortex radial distance. Motivated by this suggestion, we consider a family of scalings for the velocity as a distance function from the vortex axis to the general power b > 0. This leads to a boundary-value problem for a system of nonlinear differential equations. We analyze this problem for particular cases, both with nonzero and zero viscosity, discuss the question of existence of solutions, and use numerical techniques to describe those solutions that we cannot obtain analytically.


March 26, 2015

Alexei Stuchebrukhov, University of California - Davis


April 2, 2015

Michael Ramsey-Musolf, University of Massachusetts - Amherst

Fundamental Symmetries of the Early Universe and the Origin of Matter

Abstract: Explaining why the universe contains more matter than antimatter remains an open problem at the interface of particle and nuclear physics with cosmology. While the Standard Model of particle physics cannot provide an explanation, various candidates for physics beyond the Standard Model may do so by breaking fundamental symmetries. Among the most interesting and testable scenarios are those that would have generated the matter-antimatter asymmetry roughly 10 picoseconds after the Big Bang. I discuss recent theoretical ideas for such scenarios, developments in computing their dynamics, and prospects for testing their viability with measurements at the high energy and high-intensity frontiers.


April 9, 2015

Hitoshi Murayama, Kavli IPMU and University of California - Berkeley

Vaden Miles Lecture: The Quantum Universe

Abstract: Where do we come from? Science is making progress on this age-old question of humankind. The Universe was once much smaller than the size of an atom. Small things mattered in the small Universe, where quantum physics dominated the scene.

To understand the way the Universe is today, we have to solve remaining major puzzles. The Higgs boson that was discovered recently is holding our body together from evaporating in a nanosecond. But we still do not know what exactly it is. The mysterious dark matter is holding the galaxy together, and we would not have been born without it. But nobody has seen it directly. And what is the very beginning of the Universe?


April 14, 2015

Isaak Balberg, The Hebrew University of Jerusalem

Staircase Percolation

Abstract: Percolation is about the global properties of systems where the constituents of the system are connected by some given locally defined criterion. The common feature of the behavior of all those properties is that they depend on the density of the constituents, Ï, as do physical properties in well-known phase transitions. Correspondingly, percolation theory was found useful to describe and understand various phenomena from quark systems scales to the galactic scales [1]. The recent theory of staircase percolation is concerned with percolation systems where the local connectivity criterion changes, qualitatively and/or quantitatively, with the increase of Ï. In this talk, the staircase behavior will be described in particular in terms of electrical networks where the local criterion is changing, through discrete or continuous values, with Ï. Theoretical [2], computational [3] and experimental [4] results that demonstrate this behavior will be presented.

[1] Continuum Percolation, I. Balberg, volume 2, of the Springer Encyclopedia of Complexity and systems science (Springer, New York, 2009), pp. 1443-1475.

[2] The percolation staircase model and its manifestation in composite materials, I. Balberg, D. Azulay, Y. Goldstein, J. Jedrzejewski, G. Ravid and E. Savir, Euro. Phys. J. B, 86, 428, 1-17 (2013). See also Europhysics News, Highlights 45 (1) 08 (2014).

[3] Percolation-to-tunneling crossover in conductor-insulator composites, G. Ambrosetti, I. Balberg, and C. Grimaldi, Phys. Rev. B, 82, 134201; 1-7 (2010).

[4] Vladation of the tunneling percolation staircase model in granular metals, I. Balberg, D. Azulay, J. Jedrzejewski and E. Savir, Appl. Phys. Lett. 104, 253109; 1-4 (2014).

Fall 2014

September 4, 2014

Paul Martini, Ohio State University

The Mystery of Dust in Early-Type Galaxies

Abstract: Approximately half of all early-type galaxies are observed to have dust, yet the origin of this dust remains a mystery. Two origins have been proposed to explain the dust: creation in the stellar winds of their evolved stellar populations and the accretion of dusty satellites, yet neither appears to be completely successful. In order to resolve this issue, I have fit dust models and estimated dust masses (or established upper limits) for a representative sample of early-type galaxies with mid- to far-IR photometry. I will present a demographic analysis of the dust mass distribution in these galaxies and combine estimates of the expected rate of internal production, the rate of dusty satellite accretion, and the dust destruction timescale to explain the origin of the dust.


September 11, 2014

Christopher Li, Drexel University

Functional Polymer Single Crystals

Abstract: Seventy-five years after Storks reported gutta-percha single crystals obtained by casting thin films from dilute chloroform solution, and suggested a possible chain folding mechanism in polymer crystallization, a library of beautiful polymer single crystals (PSCs) has been grown in the lab. Unfortunately, compared with the fast-growing metallic or semiconducting nanoparticles, PSCs lack functions and they are often used as the "model" system to determine polymer crystal structures. In this presentation, I will discuss our recent efforts on designing and growing functional PSCs by using tailor-made polymers, and by controlling chain folding upon crystallization. The functional groups of the polymer can be precisely located on lamellar surface. The resultant "sticky" surface can then be used to selectively immobilized nanoparticles to form nanoparticle-PSC nanosandwiches. This unique nano ensemble is highly functional; possible applications range from surface-enhanced Raman, artificial nanomotor, to drug/gene delivery. It also enables facile synthesis of asymmetrically functionalized nanoparticles. Biomimetic mineralization can also be achieved when combining block copolymer single crystals and 1D nucleation.


September 16, 2014

Carl Wieman, Stanford University

Taking a Scientific Approach to Science Education

Abstract: Guided by experimental tests of theory and practice, science has advanced rapidly in the past 500 years. Guided primarily by tradition and dogma, science education meanwhile has remained largely medieval. Research on how people learn is now revealing much more effective ways to teach and evaluate learning than what is in use in the traditional science class. The combination of this research with information technology is setting the stage for a new approach to teaching and learning that can provide the relevant and effective science education for all students that is needed for the 21st century.


September 25, 2014

Jian Huang, WSU

Quantum Wigner Solids in Two-dimensional Flatlands

Abstract: Transport studies of two-dimensional electron systems compose two fundamental effects: disorder scattering and electron-electron interaction. Fifty years after Anderson's theory of localization for non-interacting electrons, the question of whether and how electron-electron interaction qualitatively alters the many-body states is still unsettled. The most prominent interaction-driven phenomenon is the Wigner crystallization (WC) of charges. Such a fascinating quantum state of matter (with spin ordering) can be utilized for futuristic applications including quantum electronics and spintronics. The classical version of the WC, with the Coulomb energy less than the Debye temperature, has been demonstrated in electrons on a helium surface. On the other hand, the more desired quantum version, with a Coulomb energy much less than the Debye temperature, has not been previously observed in a zero magnetic field. This colloquia reviews important progress made over the past four decades as understandings of the interplay of disorder and interaction are developed. Recent experimental results we obtained from measuring a novel type of ultra-high purity semiconductor systems will be presented as evidence for interaction-driven nature of the many-body states, including a threshold transport characteristic as a probable evidence of a quantum Wigner Crystal.


October 2, 2014

Will Clarkson, University of Michigan - Dearborn

New adventures of an Old Bulge; the Milky Way Bulge in the 21st century

Abstract: The last decade has seen a revolution in our understanding of galaxy bulges, including the bulge of our own Milky Way galaxy. Containing a significant fraction of the stellar mass in most disk galaxies, these roughly spheroidal structures are important players in the formation and evolution of galaxies through cosmic time. Since the Milky Way bulge is so much closer than those of even the nearest galaxies, models can be tested to a level of detail simply not observationally feasible for any exterior galaxy, and thus our own bulge is a vital object to understand if we wish to make progress in understanding structure formation in the Universe.

Despite careful observation, however, several basic parameters of the Milky Way bulge have been controversial for decades, since measurement of a major galactic component from within the same galaxy presents special challenges of its own. Some of the questions to be settled include: (i) exactly which way is our own Milky Way bulge oriented? (ii) Are bulge stars indeed entirely "old," or have there been recent waves of star formation within the bulge over the last few billion years? For that matter, (iii) how many structures are present (e.g. single "bulge" vs "bar" vs "bar plus bulge")?

A number of highly complementary observing campaigns are starting to shed light on these questions, with some startling recent results. I will present current indications from a number of these campaigns, both from the ground and space and highlight some of the exciting opportunities we can expect as the next generation of large ground-based surveys come online in the next decade.


October 9, 2014

Daniel McKinsey, Yale University

Direct Dark Matter Searches using Liquid Xenon: Latest Results from LUX and Prospects for LZ

Abstract: The LUX (Large Underground Xenon) experiment is designed for the direct detection of dark matter particles via their collisions with xenon nuclei. This two-phase xenon time-projection chamber, operating at the Sanford Underground Research Facility (Lead, South Dakota), was cooled and filled in February 2013. Results will be presented from the first dark matter search data set, taken during the period April to August 2013 and corresponding to 85.3 live-days of data with a fiducial mass of 118 kg. The experiment exhibited a sensitivity to spin-independent WIMP-nucleon elastic scattering with a minimum upper limit on the cross section of 7.6 x 10^-46 cm^2 at a WIMP mass of 33 GeV/c^2. The LUX results are inconsistent with the low-mass WIMP signal interpretations of data from several recent direct detection experiments. This talk will provide an overview of the LUX experiment, focusing on the recent science results. I will also describe the next-generation LZ detector, planned to have an active liquid xenon mass of 7000 kg.


October 16, 2014

Takeshi Sakamoto, WSU

Two molecules are enough to move processively

Abstract: Transportation of cargo such as vesicles, mRNA and protein complexes is an essential cellular process indispensable for life. Class V myosin proteins are molecular motors that transport such cargo along actin filaments in cells. In vertebrates, there are three isoforms of myosin V (myoV) myosin Va, Vb and Vc. MyoVa and MyoVb are processive motors, meaning that they take multiple "steps" along an actin filament each time they bind which is a trait that is clearly helpful when serving as a cargo transporting motor. It has been shown that a single molecule of MyoVa can move artificial cargo (polymer beads) along actin filaments in vitro experiments. However, MyoVc is not processive as a single molecule and cannot move a bead along an actin filament when only one MyoVc is bound. Thus, the question of whether multiple molecules of MyoVc bind to a cargo could effectively move the cargo remains largely unaddressed. Using single-molecule and protein-engineering techniques, the projects will reveal a novel possibility that non-processive molecular motors demonstrate processive activities by forming multimers multiple molecules on a scaffold working together. This, in turn, will enhance our understanding of the physical principal of cargo transport in living systems.


October 23, 2014

Giovanni Bonvicini, WSU

Beam-beam monitoring at high-intensity accelerators

Abstract: After a summary of the mathematical framework of modern accelerators, the techniques used to monitor and optimize high intensity colliding beams are reviewed. A brief history of the Stanford Linear Collider and KEKB accelerators shows where and how better beam diagnostics improved or changed drastically the delivered luminosity and physics reach of an accelerator.

A technique completely developed at WSU is at the forefront of future research in the field. It consists in the detection of large angle (much greater than 1/gamma) radiation from the beam-beam interaction and its polarization. The technique overcomes an electrodynamics theorem by observing radiation only in restricted azimuthal regions. Current activities are presented.


October 30, 2014

Abhijit Majumder, WSU

Stoking the little bang: Using jets to study the Quark Gluon Plasma

Abstract: After the discovery of the de-confined Quark-Gluon Plasma at the Relativistic Heavy Ion Collider (RHIC), the focus of the high-energy nuclear physics community (both at RHIC and LHC) has moved towards a detailed study of the structure of this exotic form of inviscid liquid matter. To date, there is no realistic microscopic theory that can describe the vanishingly small value of viscosity to entropy density or the rapid thermalization that must occur in the collision of ions at high energy. Efforts are currently underway to elucidate the structure of this substance using high-resolution probes, offered by very high energy jets. Jets are near-collinear cascades of quarks and gluons with energies that are orders of magnitude above those in the plasma. These interact with the medium and escape with a modified profile, eventually turning into a collimated spray of hadrons. I will discuss the latest results in this study, highlighting what has been learnt so far, in particular, the Wayne State led study of the temperature dependence of jet transport coefficients. I will conclude with a discussion of future directions and opportunities in this rapidly changing field of research.


November 13, 2014

André de Gouvêa, Northwestern University

The Brave Nu World

Abstract: Nonzero neutrino masses are the most concrete evidence of physics beyond the standard model to date. I will provide an overview of the current status of neutrino physics, concentrating on recent experimental and theoretical developments. I will also discuss outstanding experimental and theoretical issues and the program that is required in order to fully explore the neutrino mass puzzle, which ranges from precision neutrino oscillation searches to searches for charged-lepton flavor violation to the pursuit of a finite proton lifetime.


December 4, 2014

Alexandre V. Morozov, Rutgers University

Statistical Mechanics of Random Walks and Molecular Evolution

Abstract: Understanding the properties of transport on complex networks is crucial for quantitative analysis of numerous biological, social, and technological systems, from protein interaction networks in biology to the World Wide Web. While transport on networks with unweighted edges can be described using renormalization techniques, few analytical results are available for weighted networks, such as those describing evolutionary dynamics on fitness landscapes, chemical reactions, or protein folding. In this talk, I will describe an efficient computational approach that can be used to study random walks on weighted networks and landscapes of arbitrary complexity. After demonstrating our approach on simple examples, I will apply it to the problem of protein adaptation caused by a change in the cell's chemical or physical environment. Specifically, I will investigate how structural coupling between protein folding and binding (the fact that most proteins can only function when folded) gives rise to evolutionary coupling between the traits of folding stability and binding strength, facilitating the emergence of evolutionary "spandrels" (features that appear through adaptation even though the feature itself does not contribute to the organism's fitness).

Winter 2014

January 16, 2014

Oliver Busch, University of Heidelberg

Jet Results in pp and Pb-Pb collisions at ALICE

Abstract: Jets are defined in QCD as cascades of consecutive emission of partons from an initial hard scattering. The process of parton showering and subsequent hadronisation is broadly known as fragmentation. High energy nucleus-nucleus collisions allow us to probe parton fragmentation within a QCD medium and the properties of this medium via the modification of the
jet spectrum and jet structure. Jet reconstruction in pp collisions provides an elementary baseline and allows to investigate
perturbative and non-perturbative aspects of particle production.

The Large Hadron Collider (LHC) at CERN delivered in 2010 and 2011 heavy-ion collisions (Pb-Pb) with collision energy per nucleon pair of $sqrt{s_{NN}}$ = 2.76 TeV and pp collisions at $sqrt{s}$ = 7 TeV. ALICE at the LHC is a general-purpose heavy ion experiment designed to study the physics of strongly interacting matter and the Quark-Gluon-Plasma, combining excellent charged particle reconstruction over a wide momentum range with electromagnetic calorimetry. We present measurements of jet production cross sections, jet structure and jet fragmentation for charged particle jets and full jets in Pb-Pb and pp collisions. The results are confronted with theory predictions. We discuss perspectives for particle identification in jets with ALICE.


January 23, 2014

Professor Charles Lyndeman, Oakland University

The Geometric Clutch: A Physical Model that can explain sperm motility

Abstract: Cilia and flagella are hair-like structures of living cells that can beat back and forth and like a propeller to generate fluid propulsion. Inside of every cilium or flagellum are nine double microtubules that have dynein motor proteins arranged along their length. The Geometric Clutch hypothesis proposes that the stress that develops between the doublet microtubules regulates the action of the motors. Transverse stress perpendicular to the long axis of the cilium or flagellum can push the doublet microtubules together to engage the motors. When the cilium or flagellum bends, the stress within the structure can also pry the doublets apart to disengage the motors. A computer program utilizing this simple physical principle can successfully simulate most of the observed behaviors of living cilia and flagella, including the swimming of sperm cells.


January 30, 2014

Marguerite Tonjes, Univ. of Maryland

Probing the Quark-Gluon Plasma with High Energy Jets at the LHC

Abstract: In ultra-relativistic heavy ion collisions, a new phase of matter is produced, the strongly interacting Quark-Gluon Plasma (QGP). Jets are defined as collimated bunches of hadrons which result from quarks and gluons produced in a high-energy process such as a hard scattering. The quenching, or reduction in energy, of jets in the most energetic PbPb collisions is due to their interaction with the QGP. The high collision energy at the Large Hadron Collider (LHC) in Geneva, Switzerland provides copious production of jets with energies that can be cleanly identified above the lower energy heavy ion collision background. The multipurpose Compact Muon Solenoid (CMS) detector is well designed to measure these hard scattering processes with its high resolution calorimeters and high precision silicon tracker. The study of events with jets measured in CMS at the LHC will be presented for PbPb and pPb collision data. The analyses presented add to the understanding of this new phase of matter produced in ultra-relativistic heavy ion collisions.


February 4, 2014

Bill Llope, Rice Univ.

The Phase Diagram of Nuclear Matter

Abstract: By colliding atomic nuclei at specific beam energies, one can form systems of equilibrated nuclear matter at elevated densities and temperatures. These systems expand and cool and result in numerous sub-atomic particles that can be measured by detectors surrounding the collision. Using this information, one can infer features of the hot and dense nuclear matter that depend strongly on the beam energy. Somewhat amazingly, many of these features can be understood in the context of a phase diagram, despite the fact that the number of constituent particles in these systems is some twenty orders of magnitude smaller than Avagadro's number. A phase diagram indicates the conditions at which thermodynamically distinct phases of a substance can occur at equilibrium, and is inarguably the most fundamental information that one can have on that substance. This talk will explore the phase diagram of nuclear matter, which is relevant not only to the physics of nucleus-nucleus collisions but also the cores of neutron stars and universe a few microseconds after the big bang. The basic landscape of this diagram is presently understood, but only rather coarsely. Important details, such as the precise
locations, if not the existence, of different phase boundaries remain largely speculative. There is also the possibility that a critical point might exist. The status will be described, drawing heavily on the data from the Relativistic Heavy-Ion Collider (RHIC) as measured by the Solenoidal Tracker at RHIC (STAR).


February 6, 2014

Professor Philip Nelson, Department of Physics and Astronomy, University of Pennsylvania

Physics of human and superhuman vision

Abstract: Scientists often seem to be asking obscure theoretical questions. But sometimes, asking such questions and doggedly following the answers leads to unexpected practical payoffs, as well as deep insights into how the world works. I'll explore how the question, "What is light?" led to an understanding of how we see, and also to some powerful new ways to see things. These advances have recently given us breathtaking results in biomedical imaging, and new ways to break through a resolution barrier that had been thought sacred for over a hundred years.


February 13, 2014

Rosi Reed, WSU

Jet quenching in relativistic heavy-ion collisions: shedding light on the Quark Gluon Plasma

Abstract: In relativistic heavy-ion collisions a hot, dense medium of strongly interacting matter called the Quark Gluon Plasma (QGP) is formed. These collisions have been studied with great success at the Relativistic Heavy Ion Collider (RHIC) for over a decade. One important observation of the QGP that has come from this data is that jets of hadrons, created from the fragmentation of hard-scattered partons (quarks or gluons), are suppressed relative to scaled proton-proton collisions. This suppression, due to medium induced radiation by the parton, is called jet quenching. At the Large Hadron Collider (LHC), the collision energy was increased over an order of magnitude compared to RHIC, which increases the parton cross-section, allowing jets to be reconstructed over a wider kinematic range. Results from heavy-ion measurements from the ALICE detector will be shown and compared to both RHIC and other LHC experiments. A discussion of the models used to extract key parameters, such as the jet quenching parameter qhat, will be motivated from the results. In order to fully understand how partons lose energy in the medium, we can look at the modification of the jet structure in addition to measuring the nuclear modification factor. Jet quenching indicates that the QGP created in these heavy-ion collisions is both dense and opaque, and with the greater statistics and kinematic reach of the LHC, the QGP properties can be better quantified.


February 20, 2014

Sean Sun, Johns Hopkins University


February 27, 2014

Alexander Schmah, LBNL

From Flow to Jets, Recent Results from STAR

Abstract: A Beam Energy Scan (BES) program was carried out at RHIC to find signatures for a QCD phase transition and for a critical point. I will give an overview of various observables studied by STAR to identify those structures in the QCD phase diagram. The focus is on recent results from the energy and centrality dependence of identified particle elliptic flow. In will furthermore give an outlook on the BES phase II program which is anticipated for the years 2018-2019.

New developments in jet reconstruction in combination with high statistics data collected in 2011 changed significantly the ability of STAR to do full jet reconstruction at top RHIC energies. First results, using a new mixed event technique to characterize the combinatorial jet background, will be discussed in the second part of the presentation.


March 20, 2014

Dr. R. Perna, University of Stony Brook

Gamma-Ray Bursts as Tools for Extragalactic Astrophysics and Cosmology

Abstract: Gamma-Ray Bursts (GRBs) are the brightest light sources in the Universe, as well as the most distant sources known. These characteristics, combined with their power law spectra, make them ideal cosmological probes. In this talk I will discuss how GRBs are impacting several areas of cosmology. In particular, I will show how they can be used to trace the evolution of the mean density and clumpiness of the interstellar medium with redshift, and the properties of dust in high-z galaxies. Detection of GRBs at very high redshifts can help set constraints on the small-scale power spectrum of density fluctuations. High-resolution observations of long GRBs allow to shed light on the properties of their massive star progenitors. Statistical studies of short GRBs can improve our understanding of evolutionary binary scenarios.


March 27, 2014

Monica Brockmeyer (Assoc. Provost for Student Success), WSU

Student Success and Learning Communities

Abstract: Learning communities and other high impact practices have had a transformative effect on student learning in many universities and in many areas of study. These highly engaged forms of student learning create conditions where students can truly thrive and have positive effects on student learning that persist beyond the single class or semester. High impact practices, including learning communities, may be particularly useful in physics and other science domains, since nationally, far too many students who enter college with science aspirations leave the sciences and graduate in other disciplines. There has been much discussion of the urgent need nationally for a more scientifically prepared domestic workforce and citizenry. In this talk, we will have a conversation about how learning communities, high impact practices, and other components of the WSU Student Success initiative can be leveraged within the the Physics program.


April 8, 2014

Jamie Nagle, Univ. of Colorado (Boulder)

Discovery to Precision to Discovery: Quark-Gluon Plasma Physics

Abstract: At temperatures in the trillions of Kelvin, our theory of the nuclear force predicts that quarks and gluons are deconfined in a state of matter called the quark-gluon plasma (QGP). The Relativistic Heavy Ion Collider (RHIC) was constructed over 10 years ago to create this matter in the laboratory for experimental investigation. QGP is created and turns out to have some very remarkable properties - such as flowing as a nearly inviscid fluid. Utilizing heavy ion collisions at the Large Hadron Collider (LHC) has added substantially to this picture of the QGP. However, recent measurements indicate that the conditions required to thermalize QGP matter may be less stringent than previously thought. In the talk, we detail the discoveries of the last decade and the path forward at RHIC and the LHC that involve both precision measurements and opening doors for new discovery.


April 10, 2014

Vaden Miles Lecture: Mario Livio, Space Telescope Science Institute, Baltimore


April 17, 2014

Professor Paul Selvin, Department of Physics, University of Illinois Urbana-champaign

Fall 2013

September 5, 2013

Nilton Renno, UofM

Exploring Mars with the Curiosity Rover

Abstract: The Mars Science Laboratory Curiosity Rover was developed to assess if Mars could sustain microbial life. Since liquid water is a basic ingredient for life as we know it, in order to understand the potential for life to exist in other planets, we must first understand the behavior of water on them. In this presentation, the Curiosity Rover, its instruments, and its landing site on Mars will be described briefly. Then, the current evidence for water on Mars will be discussed. The presentation will conclude with a discussion of Curiosity's initial results.


September 19, 2013

Gavin Lawes, WSU

Spin-Charge Coupling in Vanadates

Abstract: The recent interest in materials exhibiting strong coupling between charge and spin degrees of freedom is motivated in part by the new applications that can be developed using these systems. This magnetoelectric coupling means that the magnetic properties are changed in an electric field or, conversely, the electric properties by a magnetic field. One particularly interesting class of such materials include certain transition metal vanadates, oxides incorporating non-magnetic vanadium ions with magnetic transition metals. These include multiferroic systems such as Ni3V2O8 and FeVO4, which have simultaneous magnetic and ferroelectric order, together with related materials such as Co3V2O8 and Mn3V2O8. This coupling between spin and charge can be qualitatively understood using a Ginzburg Landau mean-field approach, which incorporates higher order magnetoelectric terms coupling the magnetic and ferroelectric order parameters. More generally, I will discuss the development of magnetoelectric coupling in these transition metal vanadates. I will conclude with some brief comments about what we can learn about the microscopic coupling between charge, spin, and lattice degrees of freedom in these fascinating materials.


September 26, 2013

Michael Sokoloff, Univ. of Cincinnati

Studies of Charm Mixing and CP Violation Using D0 -> K pi Decays

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October 3, 2013

Rosi Reed, Yale Univ.

Jet quenching in relativistic heavy-ion collisions: shedding light on the Quark Gluon Plasma

Abstract: In relativistic heavy-ion collisions a hot, dense medium of strongly interacting matter called the Quark Gluon Plasma (QGP) is formed. These collisions have been studied with great success at the Relativistic Heavy Ion Collider (RHIC) for over a decade. One important observation of the QGP that has come from this data is that jets of hadrons, created from the fragmentation of hard-scattered partons (quarks or gluons), are suppressed relative to scaled proton-proton collisions. This suppression, due to medium induced radiation by the parton, is called jet quenching. At the Large Hadron Collider (LHC), the collision energy was increased over an order of magnitude compared to RHIC, which increases the parton cross-section, allowing jets to be reconstructed over a wider kinematic range. Results from heavy-ion measurements from the ALICE detector will be shown and compared to both RHIC and other LHC experiments. Jet quenching indicates that the QGP created in these heavy-ion collisions is both dense and opaque, and with the greater statistics and kinematic reach of the LHC, the QGP properties can be better quantified.


October 10, 2013

Thomas Ullrich, BNL

The Glue That Binds Us All - Probing Gluonic Matter With the World's First Electron-Ion Collider

Abstract: Gluons determine all the unique features of the strong interactions. Their self-interactions lead to their dominant abundance inside matter. Despite their dominant role, the properties of gluons in matter remain largely unexplored. We have been able to address certain aspects through experiments in electron-proton collisions and have found tantalizing hints of saturated gluon densities in proton-nucleus collisions at the highest energies. But getting to the heart of the matter, unveiling the collective behavior of dense assemblies of gluons under conditions where their self-interactions dominate will require an Electron-Ion Collider: a new facility with capabilities well beyond those of any existing accelerator, a machine that can radically transform our understanding of key features of the strong interactions. In this talk, I will outline the compelling physics case for an EIC and discuss briefly the progress towards the realization of such a machine.


October 17, 2013

Richard Hill, Univ. of Chicago

Standard Model anatomy of dark matter detection

Abstract: Despite compelling evidence for its existence, the particle nature of cosmological dark matter remains unknown. The recent discovery of a Standard Model-like Higgs boson and the hitherto absence of evidence for other new states provides important guidance for this search. I survey the theoretical landscape of dark matter candidates and discuss new advances in Standard Model calculations, some borrowed from heavy quark physics, that constrain how dark matter can interact with ordinary matter, irrespective of its detailed composition. I describe the status and future prospects for dark matter searches, focusing on direct detection in underground laboratories.


October 24, 2013

Kristen Verhey, Professor, University of Michigan

Kinesin-3 motors, the marathon runners of the cellular world

Abstract: Long-distance intracellular transport is carried out by the microtubule-based motor proteins kinesin and dynein. The kinesin-3 family is one of the largest among the kinesin superfamily and consists of five subfamilies in mammals (KIF1, KIF13, KIF14, KIF16, and KIF28) associated with diverse cellular and physiological functions including vesicle transport, signaling, mitosis, nuclear migration, viral trafficking, and development. Defects in kinesin-3 transport have been implicated in a wide variety of neurodegenerative, developmental and cancer diseases. A mechanistic understanding of this important class of cellular transporters is limited to studies of truncated versions of mammalian KIF1A and its homolog C. elegans UNC-104, and these studies have yielded contradictory results. Analysis of other kinesin-3 family members has not been carried out. Thus, in spite of their widespread functions and clinical importance, the mechanisms of kinesin-3 motor regulation and motility remain largely unknown.

We performed a comprehensive analysis of mammalian kinesin-3 motors from three different subfamilies (KIF1, KIF13, and KIF16). We find that kinesin-3 motors employ a unique mechanism of regulation in which non-cargo-bound motors are monomeric and inactive whereas cargo-bound motors are dimeric and processive. The molecular mechanisms that regulate the monomer-to-dimer transition center around the neck-coil (NC) segment and its ability to undergo intramolecular interactions in the monomer state versus intermolecular interactions in the dimer state. In the case of KIF13A and KIF13B, we suggest a novel mechanism that dimerization requires the release of a proline-induced U-turn between the NC and subsequent CC1 segments. We show that dimerization of kinesin-3 motors results in highly processive motion, with average run-lengths of ~ 10 micrometer, and that this property is intrinsic to the kinesin-3 motor domain. Such high processivity has not been observed for any other motor proteins and suggests that kinesin-3 motors are evolutionarily adapted to serve as the marathon runners of the cellular world.


October 31, 2013

Claude Pruneau, WSU

Perils from Space

Abstract: The recent impact of a large meteor in Russia on February 15, 2013, reminds us that the Universe is a very dangerous place. Large impacts are relatively infrequent but they do happen! I will present a survey of large meteoritic impacts on Earth and discuss the origins of these large objects. I will also present a summary of efforts conducted nationally and internationally to detect potentially hazardous asteroids (PHAs), i.e. asteroids with orbits that bring them periodically near Earth. I will conclude with a brief discussion of techniques envisioned to avert or mitigate the effects of potential impacts.


November 7, 2013

Christopher Yengo, Pennsylvania state university

Structural Mechanism of Actomyosin-Based Force Generation

Abstract: Myosins utilize a conserved structural mechanism to convert the energy from ATP hydrolysis to a large swing in the force generating lever-arm. However, there remains an ongoing controversy about the kinetics of lever-arm swing in relation to the steps in the ATPase cycle. To address this question we have developed a novel FRET system in myosin V (MV) that utilizes several donor-acceptor pairs to examine the dynamics of lever arm motion. MV containing a single IQ motif and an N-terminal (NT) tetracysteine site was labeled with the bisarsenical dye FlAsH (MV.NT.FlAsH). The first IQ motif of MV.NT.FlAsH was exchanged either with IAANS labeled CaM, a donor, or QSY-9 labeled CaM, a non-fluorescent acceptor. Steady-state and transient kinetic experiments reveal a decrease in FRET upon ATP binding (recovery stroke) in both donor-acceptor pairs. We utilized transient kinetic experiments to demonstrate that upon mixing the MV.ADP.Pi complex with actin there was a FRET increase that occurred in two phases, and the fast and slow phases correlated well with the release rates of Pi and ADP, respectively. We also labeled the upper-50kDa tetracysteine site with FlAsH (MV.U50.FlAsH) and exchanged the QSY labeled CaM on to the first IQ motif. We observed structural changes during ATP binding that were very similar to the MV.NT.FlAsH results. During actin-activated product release we observed two-phases, a rapid increase in FRET followed by a slower decrease in FRET, which correlated well with ADP release. We find that the force generating motion of the lever arm occurs in two steps which are closely coupled to the product release steps. Our results also indicate that the conformational changes in the lever arm associated with the power stroke may follow a unique pathway that is not simply the reversal of the recovery stroke.


November 14, 2013

Larry McLerran, BNL

New Form of High Energy Density Matter

Abstract: I describe possible forms of high energy density strongly interacting matter. The Color Glass Condensate (CGC) is a highly coherent high density state of gluons. The CGC forms an important part of the wave function for a strongly interacting particle, and is responsible for producing matter in typical high energy scattering events. The Plasma is the matter produced from collisions. It too is highly coherent, and very probably behaves as a nearly non-viscous fluid. At early times it is thought of as strongly interacting color electric and color magnetic fields. It may form a Bose condensate, and support phenomena such as solitons or parity violating fluctuations. The Plasma eventually forms a thermalized strongly interacting Quark-Gluon Plasma, which is also a nearly viscous fluid. The description I give will be related to experimental results arising from experiments at Brookhaven Lab. and CERN.


November 21, 2013

Andy Rundquist, Hamline Univ.

Physics education engineering

Abstract: I decide what to do in my next class by looking at what makes me crabby in my current class. This has led me to pedagogical experiments ranging from flipping my teaching to standards-based grading with voice. The former has helped me use my precious class time, and the latter has turned upside-down my notions of assessment and evaluation. My students now make videos of their work, and I find I'm spending as much time on accuracy as on attitude and enthusiasm. I feel my experiments have helped me grapple with cheating, student ownership, student agency, and my sanity. Join me for a conversation about physics teaching and, more to the point, physics learning.


December 5, 2013

Saw Hla, Ohio University

Frontiers of STM Manipulations: Imaging Atomic Spin to Operating Nanomachines

Abstract: We combine a variety of scanning tunneling microscope (STM) manipulation schemes with tunneling spectroscopy techniques to image and manipulate atoms and molecules on surfaces. This talk will highlight recent advances achieved by manipulation at atomic and molecular scale. In spintronic area, we will present imaging and manipulation of atomic spin using a spin-polarized STM tip. In nanoscale superconductivity area, donor-acceptor type charge transfer based molecular superconducting system will be discussed. Here, the finding of superconductivity in just four pairs of (BETS)2-GaCl4 molecules opens the possibility of investigating superconducting phenomena locally. In molecular machine area, we will present controlled rotation of a stand-alone multi-component molecular motor operated by injecting tunneling electrons from an STM tip. By selectively exciting different rotator arms of these molecular motors, controlled rotations into both, clockwise and counterclockwise directions have been achieved. These innovative experiments are tailored to address several critical issues covering fundamental understanding as well as demonstration of novel atom/molecule-based devices on materials surfaces.

Winter 2013

January 17, 2013

G.B. Martins, Oakland University, Rochester, MI

Electrostatic control over polarized currents through spin-orbital Kondo effect


January 24, 2013

Vladimir Shiltsev, Fermilab

Accelerators and Beams: Science, Technology and Art of Operation

Abstract: Beams of charged particles, especially high energy particles, offer unique research opportunities for many branches of physics - from particle physics and nuclear physics, to condensed matter physics or materials physics. Over more than 80 years, scientists have come a long way building accelerators of many types, which vary by characteristics of the generated particle beams such as average energy, particle type, intensity, and dimensions. We have learned that the physic of beams itself (or accelerator physics) is a very rich branch of physics. In my talk I'll briefly go over basics of accelerators, demonstrate what an interesting mix of science and technology modern accelerators are, discuss current challenges faced by accelerator builders and take a look into the prospects of future accelerators.


January 31, 2013

Chong-Yu Ruan, Michigan State University, East Lansing, MI

Probing nonequilibrium electron-phonon dynamics in Mott insulator and charge-density waves using ultrafast electron crystallography

Abstract: The coexistence of various electronic and structural phases that are close in free-energy is a hallmark in strongly correlated electron systems, where fascinating properties, such as metal-insulator transition, colossal magnetoresistance, and high-temperature superconductivity, can be induced often interchangeably by applying heat, stress, electric field, or charge carrier doping. The collective phase behavior under these tuning parameters can involve strongly cooperative electronic and structural modifications in the ordered state, hence deciphering the fundamental driving mechanism in such systems remains very active in condensed matter physics. I will outline the recent results of metal-insulator transition in vanadium dioxide and charge melting transition in 2D charge-density waves by various experiments and theories, including the nonequilibrium electron dynamics unveiled by ultrafast photoemission studies exclusively sensitive to the electronic order parameter. I will also describe the most recent findings from ultrafast electron crystallography, which provide crucial structural aspects to correlate lattice dynamics with electronic evolutions to address the two sides of a coin in the ultrafast switching of a cooperative state. These new results shed light on several controversial issues and bring forth new perspectives in understanding light-matter interactions in strongly correlated systems with many potential applications.


February 7, 2013

Jim Napolitano, Rensselaer Polytechnic Institute

Puzzles and Promise: A History of Neutrino Physics

Abstract: Neutrinos were first postulated by Pauli in a desperate attempt to save the laws of nature. Fermi built a theory out of them and, decades later, Reines and Cowan discovered them. Multiple types of neutrinos were later found, and Pontecorvo suggested they might "oscillate" between each other. After definitive observation of neutrino oscillations in the past 10-12 years, we have learned to piece together the "neutrino matrix" using several different experimental techniques. One more parameter remains, and it may hold the key to the origin of matter in the universe.

I will review the theoretical and experimental history of neutrino physics, contrasting accelerator and reactor experiments with measurements using astrophysical sources. We will focus on the findings of the last several years, and then discuss the experiments on the horizon, and their possible implications for the matter/antimatter asymmetry of the universe.


February 14, 2013

Boris Spivak, Department of Physics and Astronomy, University of Washington

A typology for quantum Hall liquids

Abstract: There is a close analogy between the response of a quantum Hall liquid to a small change in the electron density and the response of a superconductor to an externally applied magnetic flux-an analogy which is made concrete in the Cherns-Simons Landau-Ginzburg formulation of the problem. As the types of superconductors are distinguished by this response, so too quantum Hall liquids: a typology can be introduced. The Pfaffian phase of electrons in the proximity of a half-filled Landau level is understood to be a p+ip superconductor of composite fermions. We find that, as in a type one superconductors, the vortexes attract so that, upon varying in the magnetic field from its magic value at γ=5/2, the system exhibits Coulomb frustrated phase separation.


February 21, 2013

Dmitri Kharzeev, Stony Brook University

The mirror symmetry in super-dense matter and chiral hydrodynamics

Abstract: I will discuss the fate of parity invariance (mirror symmetry) in hot and dense quark-gluon matter. While parity is globally conserved in Quantum ChromoDynamics, the interplay of quantum anomalies, topology, and external magnetic field can induce local parity-odd effects. The anomaly also leads to a variety of novel effects in relativistic hydrodynamics. In particular, the local imbalance between left- and right-handed fermions in the presence of magnetic field induces the spatial separation of positive and negative electric charges ("the Chiral Magnetic Effect").

In heavy ion collisions, this effect can be detected through the separation of positive and negative hadrons with respect to the reaction plane. There is a recent evidence for charge separation from the experiments at Relativistic Heavy Ion Collider and the
Large Hadron Collider. The effect has intriguing implications for the cosmology of the early universe and has analogs in condensed matter physics (quantum wires, graphene, and topological insulators), and in astrophysics (particle acceleration in cosmic strings).


February 28, 2013

James Allen, University of Michigan, Ann Arbor

Topologically protected surface conduction in SmB6 new solution to a thirty year old mystery

Abstract: Topological insulators are arguably the most exciting new development in condensed matter physics since initial theoretical work in 2005. These materials constitute a new state of matter in which the (three-dimensional) bulk is insulating but the surface is metallic due to topologically protected surface states that disperse across the Fermi energy EF inside the bulk insulator gap. The initial theory was done for insulators which are weakly correlated and hence well described by the usual band theory so that Coulomb interactions need not be specifically included. The theory has recently been extended to predict that the so-called Kondo insulators, which are strongly correlated heavy fermion or mixed valent rare earth compounds, can also have such topologically protected surface states. Pursuing this possibility [1, 2] for the mixed valent insulator SmB6 has led to a new solution of a more than thirty year old mystery [3] concerning the electrical transport of this material.

In mixed valent materials hybridization between the f-shell and conduction band states enables quantum fluctuations of the f-shell occupation in spite of the very large f-shell Coulomb interaction that normally forces integer valence and binds the f-electrons into atomic multiplet states. SmB6 is one of the earliest known such materials. More than thirty years ago it came as a surprise to find that in spite of these quantum fluctuations a small insulating gap is indicated by an exponential increase of its resistivity with decreasing temperature (T), and it was then even more perplexing that at the lowest T the resistivity rise saturates as for a metal but at a value so high that within the framework of bulk conduction it has never been rationalized as arising either from intrinsic or impurity band states in the gap. [3] Numerous efforts over the years to eliminate this anomalously large residual resistivity have failed. Through novel electrical measurements we have now shown that this low T conductivity resides on the surface. [2] Our finding is consistent with a theoretical prediction [1] that SmB6 is a topological insulator and also resolves the old mystery in a surprising way the residual conductivity is intrinsic but not in the bulk. We argue that the robustness of the conductivity is a signature of the topological protection of the surface states.


March 7, 2013

Jerry Dunifer, Wayne State University

A Personal Tour of some Major and Historic Telescopes Around the world

Abstract: During the past three years, I have spent part of my time in retirement visiting a number of major and historic telescopes at different locations around the World. Visits to optical, radio, and gamma-ray telescopes have ranged from the US mainland to Hawaii, Chile, Puerto Rico,and the Canary Islands. In my talk I will describe some of the features of these telescopes, the characteristics of the observing sites, and the science carried out at the observatories.

March 26, 2013

M. Prakash, Ohio University

Toward a model-independent equation of state of neutron-star matter

Abstract: The largest measured mass of a neutron star establishes the ultimate energy density of observable cold baryonic matter. Implications of accurately known masses, particularly near and above 2 solar masses, for theoretical models of extreme states of matter will be highlighted. Although inherently difficult, estimates of radii in some cases are emerging. Concomitantly, techniques to determine masses and radii of individual neutron stars are being devised.

My talk will address the extent to which several measured masses and radii of individual neutron stars (with inherent
observational errors) can establish a model-independent EOS through an inversion of the stellar structure equations.
Observational advances required to make significant progress will be highlighted.


March 28, 2013

Josh Folk, University of British Columbia

Thermal measurements in interacting quantum devices

Abstract: The last twenty years have seen enormous advances in our ability to design and fabricate nanoscale electronic devices, whose properties at low temperature are dominated by quantum behaviors of the constituent electrons. Electrical (conductance) measurements of these devices have yielded valuable insights on quantum effects in low-dimensional systems, from Coulomb blockade to decoherence to Kondo effect. For all that can be learned from conductance, however, many puzzles remain unresolved, especially where many-particle interactions are strong. This talk will describe how thermal measurements can provide a resolution to some of these puzzles, and offer enhanced sensitivity to electronic states away from the Fermi level. We have studied the thermopower of a particularly simple quantum device: a narrow constriction known as a quantum point contact. Thermopower signatures offer unmistakable signs of a quasi-localized state beneath the Fermi energy, and provide some of the clearest evidence to date of strong interactions in this system.


April 4, 2013

Vaden W. Miles Memorial Lecture to be held in the Spencer M. Partrich Law School Auditorium

Charles M. Falco, College of Optical Sciences and Department of Physics, University of Arizona

The Science of Optics; The History of Art


April 9, 2013

Qian Niu, University of Texas, Austin

Berry Phase effect on Bloch electrons in electromagnetic fields

Abstract: In this talk, I will review the semiclassical theory of Bloch electrons, showing how the Berry curvatures modify the equations of motion and the phase space density of states. I will also report our recent progress on extending the theory to second order in the fields. To our surprise, the basic structure of the first order theory is preserved, and we only need to add field corrections to the Berry curvature and the band energy. As applications, I will discuss the calculation of susceptibilities of the usual electric and magnetic kinds as well as their cross type.


April 11, 2013

Peter Arnold, University of Virginia

The Landau-Pomeranchuk Migdal effect, 1953 to Today: Cosmic Rays to Quark-Gluon Plasmas to String Theory

Abstract:High-energy cosmic rays lose energy and so eventually stop in the atmosphere/earth by showering: through bremsstrahlung and pair production during scattering from the electric fields of nuclei, one initial particle splits its energy into a increasing number of lower energy particles. In the 1950's, Landau, Pomeranchuk and Migdal (LPM) worked out that the theory of showering has a complicated twist: at very high energy, successive scatterings in even a very dilute system, like the atmosphere, cannot be treated as quantum mechanically independent. I will explain what the LPM effect is and how it arises. Then I will discuss its more recent application to the theory of jet quenching in quark-gluon plasmas created in relativistic heavy ion collisions at the RHIC and the LHC colliders. Finally, I will explain how some unresolved theory issues concerning the LPM effect in strongly-interacting systems are being fruitfully explored by one of string theory's greatest feats of prestidigitation: gauge-gravity duality, which in this case manifests as a mapping of problems in certain types of strongly-coupled finite-temperature quantum field theories in 3+1 space+time dimensions into solvable *classical* field theory problems of general relativity and black holes in 4+1 space+time dimensions.

Fall 2012

September 6, 2012

Robert Harr, Wayne State University

Trapping the Higgs Boson, a Practical Guide

Abstract: On July 4, 2012, the ATLAS and CMS experiments at CERN announced the discovery of a new boson, a candidate for the long-sought Higgs boson. A few days earlier, the CDF and D0 experiments at Fermilab announced their latest results on the search for the Higgs boson, complementary to, but not as statistically significant as the CERN results. This is heralded as the biggest discovery in particle physics of the last 30 years. We'll discuss the role of the Higgs boson in the theoretical framework of particle physics, the methods that can be used to observe a Higgs boson, what signals were seen, and what additional information is needed to confirm the new boson as a Higgs boson. Some of the possible implications, if the new boson is or is not a Higgs boson, will be examined.


September 13, 2012

David Tomanek, Michigan State University

Unusual properties of designer carbon nanostructures

Abstract: Significant advances in Materials Science have been achieved by harnessing specific functionalities of nanostructures, such as improved mechanical, electrical and thermal properties, for particular applications. Predictive ab initio calculations suggest that designer nanostructures, such as schwarzites and related foam structures of carbon, may combine low gravimetric density with high stiffness and favorable electrical as well as thermal conductivity. Bundled nanotubes may spontaneously twist to ropes. Reversible nanomechanical energy storage in nanotube ropes twisted to their elastic limit exceeds significantly that of any other energy storage device. Unusual charge and thermal transport properties can be expected in peapods consisting of doped fullerenes or diamondoids enclosed in a carbon nanotube. Successful synthesis of such nanostructures precludes detailed understanding of their microscopic formation mechanism. Combination of molecular dynamics simulations and total energy calculations provide guidelines to achieving chirality selective synthesis of carbon nanotubes without metal catalyst or the formation of unusual nanostructures on carbon saturated metals. Since direct observation of such atomic-scale processes is very hard by experimental means, computer simulations are a welcome alternative to gain microscopic insight into the underlying processes.


September 20, 2012

Hendrik Schatz, Michigan State University

Understanding exploding stars with the Facility for Rare Isotope Beams

Abstract: The Facility for Rare Isotope Beams (FRIB) is under construction at Michigan State University. It will be able to produce most of the radioactive isotopes that are produced in supernova explosions and X-ray bursts, and are the progenitors of the elements found on earth today. This will enable experiments that promise to address long-standing open questions related to the origin of the elements and the nature of neutron stars. I will review recent progress in astronomy and astrophysics that makes the lack of nuclear data on radioactive isotopes a major roadblock for progress in nuclear astrophysics. I will also discuss a few recent experiments carried out at existing rare isotope facilities such as the NSCL at Michigan State University, that provide already some information on radioactive isotopes of interest for astrophysics. I will also present plans for new experimental approaches for nuclear astrophysics experiments at FRIB.


September 27, 2012

Xuan Gao, Case Western Reserve

Gate-Controlled Spin-Orbit Interaction and 1D Thermoelectric Transport in InAs Nanowires Abstract

Abstract: 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 the fundamental quantum transport and applied nanotechnology research. First, we will discuss our recent results of gate induced generation and control of the Rashba SOI 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' Fermi level through quantized one-dimensional (1D) subbands. At temperatures below c.a. 100K, large oscillations in the thermopower and power factor concomitant with the stepwise conductance increases are observed due to the formation of 1D electron sub-bands. This work experimentally demonstrates the possibility to tailor nanowire's thermoelectric properties through 1D quantum confinement effect, a long-sought goal in nanostructured thermoelectrics research.


October 4, 2012

Joe Kapusta, University of Minnesota

Accelerator Disaster Scenarios, the Unabomber, and Scientific Risks

Abstract: The possibility that experiments at high-energy accelerators could create new forms of matter that would ultimately destroy the Earth has been considered several times in the past 35 years. One consequence of the earliest of these disaster scenarios was that the authors of a 1993 article in Physics Today who reviewed the experiments that had been carried out at the Bevalac at Lawrence Berkeley Laboratory were placed on the FBI's Unabomber watch list. Later, concerns that experiments at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory might create mini black holes or nuggets of stable strange quark matter resulted in a flurry of articles in the popular press. These concerns were repeated a decade later before the Large Hadron Collider at CERN began operation. I discuss this history, as well as Richard A. Posner's provocative analysis and recommendations on how to deal with such scientific risks. I conclude that better communication between scientists and nonscientists would serve to assuage unreasonable fears and focus attention on truly serious potential threats to humankind.


October 11, 2012

Zhixian Zhou, Wayne State University

Electronics with layered systems:graphene and beyond

Abstract: Graphene is a single atomic layer of graphite that, among other unique properties, exhibits exceptionally high carrier-mobility, offering the tantalizing possibility of graphene-based electronics. A band gap, which is needed for most device applications, can be engineered by slicing graphene into nanometer-scale ribbons. However, the complication arising from the interplay between the edge effects and the disorder induced by the surface impurities and the SiO2 substrate is a major problem in the development of GNR-FET based electronics. To isolate these effects, we have performed Electrical transport measurements on suspended ultraclean GNRs with nearly atomically smooth edges revealing a high mobility exceeding 3000 cm2 V-1 s-1 and a simple activated behavior in the temperature dependence of both the minimum conductance and residual carrier density at the charge neutrality point. In addition to graphene, I will also present our recent work on the electrical transport properties of atomically thin MoS2 and MoSe2, which belong to a family of "graphene-like" 2D materials that already have a bandgap. I will show that the low mobility previously observed in back-gated MoS2 FET devices is primarily caused by the presence of a Schottky barrier at the contacts, and the intrinsic channel properties limited by phonon scattering can be observed in MoS2 and MoSe2 devices with ohmic contacts.


October 18, 2012

Csaba Csaki, Cornell University

Particle physics after the discovery of the Higgs boson

Abstract: The discovery of the Higgs boson at the LHC last summer is a major milestone for particle physics. I will explain the significance of this discovery for our understanding of particle physics, and discuss the implications of this discovery (together with the other LHC results) for what might lie beyond the standard model.


November 1, 2012

Leonid Rokhinson, Purdue University

Observation of Fractional AC Josephson Effect: The Signature of Majorana Particles

Abstract: In 1928, Dirac reconciled quantum mechanics and special relativity in a set of coupled equations which became the cornerstone of quantum mechanics. Its main prediction that every elementary particle has a complex conjugate counterpart - an antiparticle - has been confirmed by numerous experiments. A decade later Majorana showed that Dirac's equation for spin-1/2 particles can be modified to permit real wavefunctions. The complex conjugate of a real number is the number itself, which means that such particles are their own antiparticles. The most intriguing feature of Majorana particles is that in low dimensions they obey non-Abelian statistics and can be used to realize quantum gates that are topologically protected from local sources of decoherence. While the search for Majorana fermions among elementary particles is still ongoing, excitations sharing their properties may emerge in electronic systems. It has been predicted that Majorana excitations may be formed in some unconventional states of matter. I will report the observation of the fractional ac Josephson effect in a hybrid semiconductor/superconductor InSb/Nb nanowire junction, a hallmark of topological matter. When the junction is irradiated with rf frequency f at zero external magnetic field, quantized voltage steps (Shapiro steps) with a height hf/2e are observed, as is expected for conventional superconductor junctions where the supercurrent is carried by charge-2e Cooper pairs. At high fields the height of the first Shapiro step is doubled to hf/e, suggesting that the supercurrent is carried by charge-e quasiparticles. This is a unique signature of Majorana fermions, elusive particles predicted ca. 80 years ago.


November 8, 2012

Gunther Roland, MIT

Trillion degree matter

Abstract: In this talk, I will discuss a very simple question: What are the properties of matter at extremely high temperature, in excess of several trillion Kelvin? Experiments at large particle colliders like RHIC at Brookhaven Lab and LHC at CERN have shown that such temperatures can be achieved in collisions of heavy nuclei, creating a soup of quarks and gluons resembling the universe shortly after the Big Bang. We have found that this unique state of matter exhibits fascinating and somewhat surprising properties: Although its density exceeds that of water by 16 orders of magnitude, the quark-gluon soup behaves like a near-perfect liquid. I will review the most striking observations made in recent LHC data and discuss unexpected connections to strongly coupled systems in many areas of physics, ranging from string theory to ultra-cold atoms.


November 15, 2012

Mahi Singh, University of Western Ontario

Light-matter interaction in hybrid nanomaterials

Abstract: The light-matter interactions in nano-scale hybrid materials will be discussed. Hybrid nanomaterials are fabricated by combining two or more semiconductor, metallic, or biological nanostructures. By using various combinations of these nanostructures one can create enormous numbers of nanocomposite materials. These materials have important applications in chemical and biological sensing and optical communications and information processing. When one or more external electromagnetic fields are applied to a nanocomposite system, the constituent nanostructures become optically excited. The optical excitations in semiconductor and biological nanostructures are electron-hole pairs (excitons), while excitations in metallic nanostructures are collective oscillations of electrons (plasmons). The interaction of light with a nanocomposite system can be controlled by the shape, size and relative positions of the constituent nanostructures. Therefore, these materials are an ideal platform for fundamental research on light-matter interactions and physics at the interface of classical electrodynamics and quantum mechanics. It is expected that this research will provide a basic physical understanding and development of new types of nano-devices including optical sensors and optical switches. Research on nanocomposites also has many applications in nanoscale energy transport and solar energy trapping and harvesting.


November 29, 2012

Gus Evrard, University of Michigan

Synthesizing the Sky: The Past and Future of Computational Cosmology

Abstract: In 1970, Jim Peebles modeled the Coma Cluster of galaxies with 300 point masses on a gigantic CDC "supercomputer". Since then, simulations of cosmic structure have grown dramatically in scope and scale. In this talk, I will briefly review historical development of and emerging trends in simulation methodology, highlighting specific examples of how simulations help improve cosmological studies using clusters of galaxies. I will close by commenting on challenges, including rationalizing costs associated with the largest simulations, coordinating data management of global simulation assets, and assessing the role of simulation support for large cosmic surveys aimed at studying the nature of dark energy/cosmic acceleration.


December 6, 2012

David Jiles, Iowa State University

Nonlinear magnetic modeling: breaking through the materials barrierAbstract

Abstract: When magnetic materials are exposed to external magnetic field the change in magnetization extends beyond the simple linear regime. Under these conditions it is found that the response of the materials is no longer reversible. This phenomenon, hysteresis, is well documented in the experimental literature and properties such as magnetic coercivity can range from less than 1 A/m in soft materials to 1,000,000 A/m in hard materials. Description of the non-linear response of hysteresis is a topic at the leading edge of research with important technological applications. The complexity of the problem arises because many different factors compete to determine the overall response. Therefore the description of hysteresis is poorly developed compared with the understanding of low amplitude, linear/reversible effects. In this lecture discussion will focus on the underlying concepts used to explain, and practical models used to describe, hysteresis in different materials. In general all of these descriptions are simplified approximations to complicated systems with many different and competing interactions on length scales ranging from the atomistic (10-9 m) to the macroscopic continuum (10-2 m). Therefore depending on the relative importance of the interactions, and the length scale of interest, different models are appropriate to different situations.

Winter 2012

January 31, 2012

Dr. Timothy Stasevich, Osaka University

Towards a Single Cell, Single Molecule View of Eukaryotic Gene Activation


February 2, 2012

Dr. Elena E. Dormidontova, Case Western Reserve University

Nanoparticle-Cell Surface Interactions from the Physicist's Point of View


February 9, 2012

Dr. Christopher V. Kelly, Cornell University

Observing nanoscale structure and dynamics of biological membranes


February 16, 2012

Dr. XiangQiang Chu, Oak Ridge National Lab

Neutron Scattering for Biological Sciences: Protein Dynamics and More


February 23, 2012 at 4:00pm, Room 245 of Physics Research Building

Dr. Mazin Magzoub, Yale University

Concentration-dependent transitions govern the subcellular localization of Islet Amyloid Polypeptide


March 1, 2012

J. Harton, Colorado State, AUGER


March 8, 2012

Charles Gale, McGill University

Hotter than the sun and smaller than a mosquito! Relativistic nuclear collisions: studying matter under *extreme* conditions.

Abstract: I survey recent developments in the theoretical understanding of relativistic collisions performed at RHIC, and at the LHC. Theoretical advances in the modeling of soft degrees of freedom are reviewed, and the prospect of doing tomographic studies of hot strongly interacting matter will be addressed. I will argue that the global heavy ion program is entering an era of characterization and of precision physics.


March 22, 2012

Dr. Carl A. Ventrice, Jr., University at Albany-SUNY

Graphene: a True 2-Dimensional Materials for Advanced Nanoscale Devices

Abstract: Graphene is a single atomic layer of sp2-hybridized carbon that crystallizes in the honeycomb crystal structure.One of the primary reasons for the current interest in graphene is because of its unique electrical properties. The electronic structure of graphene depends on the number of graphene layers and the stacking sequence between the layers. Single-layer graphene is a semi-metal with a linear energy dispersion near the Dirac point, which results in a very small effective mass for the carriers. On the other hand, a small energy gap can be present in bi-layer graphene, and few-layer graphene films have electrical properties that differ from single- and bi-layer graphene films and bulk graphite. In order to exploit the unique properties of graphene for device applications, it is important to develop techniques for growing graphene films over wafer-sized dimensions with uniform thickness. An overview of my research on understanding the kinetics of large-area graphene growth will be given.


March 29, 2012

Colonel Terry Virts, NASA Astronaut

Vaden Miles Memorial Lecture: Space Shuttle Mission STS-130 & Scientific Exploration on the International Space Station


April 12, 2012

Dr. Yoke Khin Yap , Michigan Tech. Physics Department

Nano, Molecular, and Quantum Electronics with Nanotubes and Nanowires

Abstract: I will discuss the following topics recently achieved in my group-Ambipolar behaviors of ZnO nanowires (NWs) were obtained for the first time by systematically incorporate hydrogen into as-grown ZnO NWs as guided by an ab initio model. Results suggest that complexes between Zn vacancies (VZn) and hydrogen can become n- or p-type carriers to initiate ambipolar behaviors in field effect transistors (FETs).Molecular electronics were investigated by using carbon nanotube (CNT) as the nanoelectrodes. This was conducted by a simple fabrication scheme with commonly available techniques including photolithography, self-assembled monolayer (SAM) of molecules, and dielectrophoretic deposition of CNTs. The characters of octadecanethiol (ODT) molecules retained in these devices as verified by scanning tunnelling microscopy (STM).Tunneling FETs were created by novel functionalized boron nitride nanotubes (f-BNNTs). Results indicate that these FETs are operational at room temperatures by tunneling with an on-off ratio of 104.


April 19, 2012

Peide (Peter) Ye, Purdue University

MoS2: 2D Crystal Beyond Graphene

Abstract: Although graphene, a single layer of carbon atoms, has superior carrier mobilities of up to 200,000 cm2/V·s, its gapless nature limits its further application in logic devices. Nevertheless, the discovery of graphene has spurred research of other two-dimensional (2D) layered structures, including boron nitride, topological insulators (Bi2Te3,Bi2Se3, etc.), and transitional metal dichalcoginides (TMDs). TMDs, e.g. MoS2, have enjoyed several advantages in device applications because they have large bandgaps (usually >1 eV), satisfactory electron mobilities of up to several hundred, good thermal stability, and can be used to form ultrathin body transistors with atomic layers, which make them a desirable channel material with superior immunity to short channel effects. In this talk, I will report on some of our new device work on MoS2and other 2D crystals focusing on high-k dielectric integration [1-2],contacts and scaling effects.

Fall 2011

September 15, 2011

Professor V. Paolone, University of Pittsburgh

Neutrino oscillations and First Results from T2K


September 22, 2011

Professor Wolfgang Bauer, Physics Dept., Michigan State University,

Solutions for the Biggest Problem in the World: Energy, Global Warming, and Advanced Biofuel Reactors

Abstract: The world economy relies on burning fossil fuels to supply the 15 TW power we currently need. But the supply of fossil fuels is finite, and oil will peak around the middle of this century. Burning fossil fuels also adds billions of tons of CO2 to the atmosphere each year and will significantly alter our climate. I will show how one can use biofuel reactors to help significantly mitigate both problems. In particular I will show that our approach is not just approximately carbon-neutral, but actually reduced the total greenhouse gas load. Our reactor also yields a factor of almost 4 more transportation fuels than conventional bioethanol production.


September 29, 2011

Dr. L. Burggraf, Air Force Institute of Technology, Dayton OH

Can we motivate a muon?


October 6, 2011

Dr. Stuart Tessmer, Michigan State University


October 13, 2011

Dr. S. Menary, York University

Trapped Antihydrogen: the Present Status and Future Plans of the ALPHA Experiment at CERN


October 20, 2011

Dr. Kenneth S. Burch, University of Toronto

Scotch Tape Method: Moving Beyond Graphene


October 27, 2011

Professor Boris Nadgorny, Wayne State University

The twisted world of Spintronics: spin transport in metals and semiconductors


November 3, 2011

Dr. Matt Johnson, Perimeter Institute,

Will the entropy of our universe always increase?


November 10, 2011

Dr. Elizabeth Simmons, Michigan State University