Physics and Astronomy Colloquium Series

• Winter 2024

  April 11, 2024

  Dr. Angela Chen, Rigetti Computing

  Scaling up quantum processors with superconducting qubits

  Abstract

  Superconducting qubit systems have become a promising platform for quantum computing due to significant material and design advances over the past two decades. To move the field closer towards practical quantum computing applications, there has been a strong focus on increasing the qubit count of quantum processors while maintaining high-fidelity gate operations.  In this talk, I will give examples of current challenges with developing superconducting qubit devices before presenting on the elements involved in making a high-performing and scalable superconducting qubit device. In particular, I will focus on one of the techniques used to achieve high-fidelity gates on smaller-scale multi-qubit devices, which entails adjusting the coupling strength between qubits. I will then show how we can scale up these devices by presenting some of our recent prototypes of modular superconducting qubit processors.

   

  April 4, 2024

  Dr. Richard Furnstahl, Ohio State University

  Fast & accurate emulation using reduced-basis methods

  Abstract

  The challenges of nuclear many-body physics have been addressed theoretically with a wide range of accurate but often computationally expensive methods. However, when we need to change the parameters characterizing the problem, such as Hamiltonian coupling constants, it can become computationally prohibitive to repeat calculations many times and challenging to reliably extrapolate. An alternative is to replace the expensive model with an *emulator*, which is an approximate computer model. In this colloquium we describe the recent development of emulators that exploit a technique called eigenvector continuation (EC); this is an adaptation of so-called reduced-basis methods used widely in engineering applications. There has been an explosion of EC applications in the last few years to nuclear structure and reactions, but the methods are broadly applicable to physics problems and can be illustrated with basic quantum mechanics.

   

  April 28, 2024

  Dr. John C. Mather, NASA

  Vaden Miles Memorial Lecture

  Opening the Infrared Treasure Chest with JWST

  Abstract

  The James Webb Space Telescope was launched on Dec. 25, 2021, and commissioning was completed in early July 2022. With its 6.5 m golden eye, and cameras and spectrometers covering 0.6 to 28 µm, Webb is already producing magnificent images and surprises about galaxies, active galactic nuclei, star-forming regions, and planets. It extends the scientific discoveries of the great Hubble, and ties the most distant galaxies to their origin story from the fluctuations of the cosmic microwave background radiation. Scientists are hunting for some of the first objects that formed after the Big Bang, the first black holes (primordial or formed in galaxies), and beginning to observe the growth of galaxies, the formation of stars and planetary systems, individual exoplanets through coronography and transit spectroscopy, and all objects in the Solar System from Mars on out. It could observe a 1 cm² bumblebee at the Earth-Moon distance, in reflected sunlight and thermal emission. I will show how we built the Webb, why we study infrared, and the most exciting current discoveries. Webb is a joint project of NASA with the European and Canadian space agencies.

  Bio

  Dr. John C. Mather is a Senior Astrophysicist and was the Senior Project Scientist for the James Webb Space Telescope (JWST) at NASA’s Goddard Space Flight Center. Since the project start in 1995 until 2023, he led the JWST science teams. As a postdoctoral fellow at NASA’s Goddard Institute for Space Studies he led the proposal efforts for the Cosmic Background Explorer (74-76), and came to GSFC to be the Study Scientist (76-88), Project Scientist (88-98), and the Principal Investigator for the Far IR Absolute Spectrophotometer (FIRAS) on COBE.  With the COBE team, he showed that the cosmic microwave background radiation has a blackbody spectrum within 50 parts per million, confirming the expanding universe model to extraordinary accuracy. The COBE team also made the first map of the hot and cold spots in the background radiation (anisotropy), the spots which nucleated the formation of galaxies. Dr. Mather received the Nobel Prize in Physics (2006) with George Smoot, for the COBE work.

   

  March 21, 2024

  Dr. Abhay Deshpande, Stony Brook University

  The EIC Science, Prospects and Possibilities

  Abstract

  In July 2018 the National Academy of Sciences, Engineering and Medicine, through their Consensus Report declared that the science of the proposed Electron Ion Collider (EIC) was compelling, fundamental and timely. The DOE office of Science followed up on the realization of the EIC and as a result the collider is almost ready to be constructed at BNL - jointly by BNL-Jefferson Lab working as partners. An international  detector collaboration (ePIC) has been formed to get detector constructed and ready for collisions by early 2030’s. In this talk, I will review  the principle pillars of the EIC science: understanding the origin of spin and mass of the proton and also, imaging the quark gluon structure and their dynamics in the protons and in nuclei at all energies available at the EIC. Part of the physics program also includes searching for a novel state of gluonic matter which QCD predicts but has not been unambiguously demonstrated to exist.  I will review the essential physics of the EIC and then conclude with the prospects of science at the EIC beyond those basic science drivers, and comment on possibility of a second detector to be built in a few years into the EIC operation.

   

  March 7, 2024

  Dr. Phiala Shanahan, MIT

  From quarks to nuclei: Computing the structure of matter

  Abstract

  Our understanding of the structure of matter, encapsulated in the Standard Model of particle physics, is that protons, neutrons, and nuclei emerge dynamically from the interactions of underlying quark and gluon degrees of freedom. In this colloquium, I will give a broad introduction and overview of the numerical lattice field theory approach to studying this structure from first principles, before focusing on some specific examples of recent progress in this field. In particular, I will describe how lattice calculations have given us new insights into the structure of the proton, including recent predictions of the contributions of gluons to its pressure and shear distributions, some of which have since been measured experimentally and others which will be measurable for the first time at the planned Electron-Ion Collider. I will also discuss how studies of light nuclei are beginning to reveal how the complexities of nuclear structure and reactions arise from the Standard Model, and how this work can provide important theory insights for searches for new physics, such as through dark matter direct detection experiments. Finally, I will explain how provably exact machine learning algorithms are providing new possibilities in this field.

   

  February 22, 2024

  Dr. Peter Onyisi, UT Austin

  The Roadmap for US Particle Physics in the Next Decade and Beyond

  Abstract

  Particle physics is a discipline that seeks to explore the fundamental nature of matter and forces in the universe, from the Big Bang until today. To do so it requires experimental efforts ranging from table-top devices to the largest machines built by humans, and extensive theoretical work ranging from precision predictions of known phenomena to invention of new paradigms and organizing principles. A large array of technologies - instrumentation, accelerators, data acquisition and computing, artificial intelligence, and microelectronics - and facilities - underground laboratories, accelerator complexes, even the South Pole and the Moon - are necessary to carry out research in the field.

   The cost and human commitment needed to engage in particle physics projects means that they need to be prioritized, keeping in mind the scientific return on investment, the overall cost envelope and the timing of various projects, and the overall balance and health of the field. They also need to be understood in the global context in which there is both collaboration and competition. The Particle Physics Project Prioritization Panel (P5), constituted roughly once a decade, is charged with reviewing project proposals for the US particle physics program over a ten year period, with a long-term vision given that the lifetime of many projects will extend far beyond that. I will discuss the report of the 2023 P5, which was released in December: the science we intend to address, the experiments that will get us there, and potential long-term futures.

   

  February 15, 2024

  Prof. Zhi-Feng Huang, Wayne State University

  Pattern Formation and Elastodynamics in Active Matter

  Abstract

  Active matter, referred to complex systems with self-sustaining energy sources or self-propulsive forces, has been of tremendous research interest in recent years. These active systems (e.g., humans, birds, bacteria, protein or colloidal motors, granular rotors, …) are intrinsically out of equilibrium, involving multiple spatial and temporal scales and exhibiting a vast variety of intriguing properties that are absent in conventional passive systems. In this talk I will introduce two of these aspects examined in our recent theoretical and computational studies, i.e., the competition between chiral particle self-propulsion and self-spinning, and effects of nonreciprocity when Newton’s 3rd law is not obeyed (the latter can be connected to non-Hermitian systems and phase transitions involving exceptional points and PT symmetry breaking). Some of the resulting novel phenomena during the formation and dynamics of active patterns will be discussed, such as the emergence of elastic wave in 2D overdamped active crystals, persistent dynamics of topological defects in active smectics, and some exotic patterns induced by vision-cone nonreciprocal interactions of single species.

   

  February 8, 2024

  Peter Jacobs, Lawrence Berkeley National Laboratory

  Condensed matter physics at the nuclear scale: probing the Quark-Gluon Plasma with jets

  Abstract

  A common theme in many-body physics is that of “emergence:” systems comprising many elementary quanta exhibit collective phenomena that cannot be predicted from the elementary interactions themselves. The Quark-Gluon Plasma (QGP), a hot fireball of quarks and gluons which is generated in collisions of heavy nuclei at the world’s most energetic accelerators, exhibits such complex emergent phenomena at the nuclear scale. How can we probe the QGP and study its structure, to understand how it works? A scattering experiment using a controlled external beam would be ideal, but is unachievable. Instead we utilize “jets,” which are the hadronic remnants of rare, hard-scattered quarks and gluons generated in the same collision as the QGP, as an internally-generated probe beam. I will describe recent measurements by the STAR experiment at RHIC and the ALICE experiment at the LHC which seek to observe Rutherford-like scattering of such jets off of quasi-particles in the QGP, and what these measurements tell us about QGP dynamics and structure. I will briefly touch on the larger program for comprehensive understanding of the QGP by the JETSCAPE Collaboration, and some of the key open questions in the field that will be addressed in the coming years.

   

  February 1, 2024

  Dr. Huey-Wen Lin, Michigan State University

  Probing the heart of the matter with supercomputers

  Abstract

  Nucleons (that is, protons and neutrons) are the building blocks of all ordinary matter, and the study of nucleon structure is a critical part of frontier research to unveil the mysteries of the universe and our existence. Gluons and quarks are the underlying degrees of freedom that explain the properties of nucleons, and fully understanding how they contribute to the properties of nucleons (such as mass or spin structure) helps to decode the last part of the Standard Model that rules our physical world. After more than half a century of large-scale experimental efforts, there are still many unknowns concerning the theory quantum chromodynamics (QCD), the branch of the Standard Model describing how gluons strongly interact with themselves and with quarks, binding both nucleons and nuclei. Using supercomputers and a theoretical tool called "lattice QCD", we can simulate the theory that dominates the universe at the femtoscale and unveil its diverse phenomenology, including some properties that are hard to determine in experiments. Few selected recent Lattice-QCD examples and their impacts will be briefly discussed.

   

  January 25, 2024

  Dr. John Heron, University of Michigan

  Electric field control of magnetism in multiferroic heterostructures

  Abstract

  Due to this collection of rich electronic phases, the complex oxides offer unparalleled opportunities for investigating correlated electron phenomena and demonstrating new proof-of-concept devices.  Modern magnetic memory technology is faced with issues of scalability and energy consumption as the required electrical current causes significant heating and stray magnetic fields. An ideal solution to this problem would be a magnetic device that can be controlled with an electric field in a capacitor structure as the electric field is well confined and minimal energy is dissipated. One issue is that the switching a magnetic device requires breaking time reversal symmetry, a symmetry that is broken by an applied current or magnetic field but not by an applied electric field. Combined ferroelectrics and magnetic materials, so called multiferroics, open pathways towards the electric field control of magnetism and energy efficient spin-based technologies. While researched for some time, critical challenges in developing new materials with large magnetoelectric coupling that can both scale to device dimension and be fast. Here I will present our results of stabilized Fe1-xGax alloys to boost (by 200-300% relative to bulk) the magnetostriction of Fe1-xGax thin film alloys by extending the phase stability of the A2 phase to higher Ga compositions. Transport-based magnetoelectric characterization of a Fe1-xGax - [Pb(Mg1/3Nb2/3)O3]0.7-[PbTiO3]0.3 (PMN-PT) composite multiferroic heterostructure shows are reversible 90° electrical switch of magnetic anisotropy and a room temperature converse magnetoelectric coefficient of 5.5×10-6 s m-1. The scaling behavior in ferroelectric and multiferroic systems are also unexplored but give rise to key questions on fundamental speed limits to the phase evolution and inherent coupling between order parameters. I will conclude the talk with our recent advancements in studying dynamic behavior in ferroic materials scaled below the domain length.

• Fall 2023

  December 7, 2023

  Dr. Cliff Burgess, McMaster University

  Thinking Effectively About Gravity

  Abstract

  We live at a time of contradictory messages about how successfully we understand gravity. General Relativity seems to work well in the Earth’s immediate neighbourhood, but arguments abound that it needs modification at very small and/or very large distances. This talk tries to put this discussion into the broader context of similar situations in other areas of physics, and summarizes some of the lessons which our good understanding of gravity in the solar system has for proponents for its modification over very long and very short distances. The main message is mixed: Some features of gravity are easier to modify than others. Also evidence from cosmology seems to prefer features (like light scalars and small vacuum energies) that are not generic to the long-wavelength limit of fundamental theories, and this is a crucial clue that would be silly to ignore. On the other hand, this clue seems difficult to use (so far) because no theories are known that everyone agrees describe all observations even in principle.

   

  November 30, 2023

  Dr. Kayhan Gultekin, University of Michigan

  Using the NANOGrav Measurements of the Gravitational Wave Background to Constrain the Supermassive Black Hole Binary Population

  Abstract

  NANOGrav has found evidence for the gravitational wave background from our pulsar timing array data. This Earth-moving new science is the result of fifteen years of work with contributions from over a hundred scientists and is consistent with other pulsar timing arrays. I will present our recent results and why we are confident in our results. I will discuss the interpretation of the background as due to a cosmic population of supermassive black hole binaries as well as other, more exotic ideas. I will present how our pulsar timing array data put constraints on the population of massive black holes and how we can improve these constraints with optical, infrared, and X-ray observations of galaxies and binary AGN.

   

  November 16, 2023

  Dr. Jesse Berezovsky, Case Western Reserve University

  Coupling and control of defect spin qubits via an engineered magnetic environment

  Abstract

  Defect spin qubits, such as the nitrogen-vacancy (NV) defect in diamond, perform splendidly as single qubits. With a coherence time that can exceed 1 s at room temperature, defect spins provide an excellent basis for single qubit devices, such as nanoscale magnetometers. But to go beyond single qubits, we require an efficient scalable platform for controlling defect spin qubit registers, and controllably coupling qubits to engineer entanglement. In this talk, I will describe recent advances in our understanding of how magnetic materials and structures couple to defect spin qubits, and how this opens an avenue towards engineering the magnetic environment of the spins for control and coupling. Topological magnetization states such as magnetic vortices provide strong, local magnetic field gradients that can be controlled dynamically for addressable control of qubits. Coupling between qubits may be enabled by a magnon-mediated process. On the other hand, spin-magnon interactions can lead to enhanced spin relaxation or decoherence. I will review recent work exploring the interactions of defect spins with magnons in adjacent magnetic structures and discuss the implications for proposed technologies incorporating coherent spins with proximal magnetic elements.

   

  November 2, 2023

  Dr. Eilat Glikman, Middlebury College

  Understanding the Role of Quasar Feedback with Red Quasars

  Abstract

  Quasars are actively growing supermassive black holes at the centers of distant galaxies. Their brightness outshines all the stars in their hosts, allowing us to study them and the universe to is earliest times. Quasar activity also regulates how galaxies and their nuclear supermassive black holes grow and co-evolve. In this talk, I will present a population of highly luminous dust-reddened quasars that may be the key to understanding this co-evolution. Red quasars are among the most intrinsically-luminous quasars in the Universe representing a short-lived phase in the lifetime of a quasar, during which their energy output (feedback) irrevocably impacts their host galaxy. Recent evidence has also shown that red quasars have enhanced radio emission, possibly linking the formation of jets to the merger phenomenon or exposing a different form of feedback in these systems, such as dusty radiation-driven winds. Red quasars are thus ideal laboratories for addressing fundamental questions on the co-evolution of black holes and their host galaxies as well as the physics of feedback. I will present findings from several surveys that are uncovering this elusive population of quasars using various selection methods across the electromagnetic spectrum to probe a broad range of redshift and luminosity regimes.

   

  October 26, 2023

  Prof. Sergei Voloshin, Wayne State University

  Swirling QGP

  Abstract

  The strongly interacting system created in ultrarelativistic nuclear collisions behaves almost as an ideal fluid with rich patterns of the velocity field exhibiting strong vortical structure. Vorticity of the fluid leads to particle polarization.  The experimental discovery of the global polarization in heavy-ion collisions, particle spin polarization along the system orbital momentum, followed by the measurements of the polarization along the beam direction, are among the most significant discoveries made in the heavy-ion collision program along with observations of strong elliptic flow and jet quenching. This discovery opened completely new perspectives for study of the nuclear collision dynamics, properties of the quark-gluon plasma (QGP), the spin and its transport in QGP medium. It generated intense theoretical discussions as well as experimental activities. In my talk I discuss several important measurements made in this field in recent years, including the most recent results from the RHIC isobar run data analysis.

   

  October 19, 2023

  Prof. Sharon Glotzer, University of Michigan

  Richard Barber and Ratna & Vaman Naik Endowed Lecture in Interdisciplinary Physics

  On the Nature of the Entropic Bond

  Abstract

  Chemical bonds are among the most fundamental concepts in science. They describe the way in which atoms associate to form molecules and compounds, and they have been a central paradigm of science for a century. Today, powerful software packages that solve quantum mechanical theories of chemical bonding are in routine use to predict molecular and crystal structures. Are analogous capabilities possible for predicting colloidal crystals, where nanoparticles play the role of atoms?  In this talk, we discuss a remarkable finding that has emerged from twenty years of global nanoscience research: Aside from differences in length, time and energy scales, atoms and nanoparticles can self-assemble into identical crystal structures, including those with large, complex unit cells. These colloidal crystal structures are possible even in the absence of explicit nanoparticle interactions, further demonstrating that statistical thermodynamics is agnostic to the forces driving self-assembly. What sort of “bonding” describes these structures, which emerge as the particles become crowded and are stabilized solely by entropy maximization? We discuss these questions and present a new theory of entropic bonding that has important analogies with chemical bonding theory. With entropic bonding theory, we can predict colloidal crystal structures from nanoparticle shape in the same way that chemical bonding theory predicts atomic crystal structures from electronic valence.

   

  September 28, 2023

  Dr. Kevin Mcfarland, University of Rochester

  Measuring the Structure of Protons with Accelerator Neutrinos

  Abstract

  High energy electron elastic scattering measurements, in which the target remains intact after the collisions, have been used to study the time-averaged structure of protons, neutrons, and atomic nuclei since the 1950s.  So it might seem surprising that such measurements using artificial beams of neutrinos had never before been performed until recently, especially given that the structure measured in such an experiment is both interesting and difficult to calculate.  I’ll discuss the technical challenges of making such a measurement, what we have found in making it, and future prospects.

   

  September 21, 2023

  Prof. Veronica Dexheimer, Kent State University

  Neutron Stars in the QCD Phase Diagram

  Abstract

  Neutron stars populate a very important part of the high-energy or QCD phase diagram, where fundamental information is currently provided by theory, laboratory experiments, and astrophysics. How to translate between results obtained from different environments that produce different conditions is one of the most important open questions in nuclear and high-energy physics today. I review the current knowledge of the QCD phase diagram and address how differences in isospin, strangeness, and magnetic field strength can modify the structure and position of deconfinement to quark matter, emphasizing on neutron star observables.

   

  September 14, 2023

  Dr. Rachael Merritt, University of Colorado Boulder

  Assessing and CURE-ing Physics Labs

  Abstract

  Physics laboratory courses offer a unique environment for education research - encompassing the evaluation of vital physics skills, the cultivation of scientific identities, and strategies for improving student retention. In this presentation, we will discuss how research-based assessment instruments (RBAIs) are useful tools for discipline-based education research and they can be used to help inform course development and improvement. We specifically look at two example RBAIs, one focused on measurement uncertainty and the other on modeling. We will also discuss the advantages of integrating course-based undergraduate research experiences (CUREs) and our ongoing initiative aimed at developing a scalable and sustainable framework for implementing CUREs within physics departments nationwide.

• Winter 2023

  April 13, 2023

  Dr. Giordon Stark, University of California Santa Cruz

  PARTY CALL PHYSICS: Likelihoods and Classifiers

  Abstract

  Communicating results between experimentalists and theorists in particle physics has been long and varied. From efficiency maps to selection cut flows - the collaboration between the two communities has continued to grow and evolve. Now, particularly more than ever, a stronger effort has been led within the ATLAS Collaboration taking advantage of the existing technologies used, such as containerization and plain-text data formats, to make analyses fully reproducible. One such data product from an experimental analysis relies on the statistical model used to derive the results published in papers, and these statistical models are essential information for analysis preservation and reuse. The ATLAS Collaboration is starting to publicly provide likelihoods associated with statistical fits used in searches for new physics. These likelihoods adhere to a specification first defined by the HistFactory p.d.f template [CERN-OPEN-2012-016]. 
  
  This talk is future-focused and will describe my efforts in improving the communication of the field along different avenues. For communicating results of experimental particle physics, I will describe how these statistical models came about, the technical developments to make this possible, and illustrate how detailed information on the statistical modeling can enhance the short- and long-term impact of experimental results. For communicating physics with for Deaf and Hard-of-Hearing members, I will show how I have worked with American Sign Language interpreters and linguistic experts developing words and concepts to ensure accurate, complete communication. These developed signs can also benefit non-signers by changing how particle physicists communicate and collaborate in a large international experiment among colleagues of diverse backgrounds, cultures, and languages. And finally, for the Early Career members of the community, I will describe where we will and can go next with the ATLAS detector.

  Bio

  Dr. Giordon Stark is a Deaf post-doctoral, experimental particle physicist involved with the ATLAS collaboration at the Santa Cruz Institute for Particle Physics, at UC Santa Cruz. He earned his PhD in Physics from University of Chicago in 2018, and a B.S in Physics from Caltech in 2012. Giordon's research focuses on looking for signs of physics Beyond the Standard Model with a particular interest in Electroweak Supersymmetry and hadronic final states. He is also passionate about boosted object reconstruction, jet substructure, pile-up mitigation techniques, designing robust hardware triggers, the intersection of particle physics & machine learning, and more! Through these efforts, Giordon has also made core contributions to improving the communication of physics results between the ATLAS Collaboration and particle physics theorists and phenomenologists. He is also leading a group of physicists within the experiment to combine and summarize the results of many BSM searches, providing key insights for the future of the successful ATLAS SUSY search program. When Giordon is not busy trying to prove the existence of SUSY, he can be found in the kitchen proving sourdoughs, baking pavlovas, and anything else he can get his hands on.

   

  April 6, 2023

  Dr. Carolyn Raithel, Princeton University

  Probing Neutron Stars with Gravitational Waves

  Abstract

  Neutron stars contain the densest stable matter in the universe. Since the first detection of gravitational waves from a binary neutron star merger in 2017, we have entered an era of multi-messenger observations of these extreme objects and their transients. However, the interpretation of these new types of data also poses new challenges for theorists working to develop to understand the dense-matter physics that govern neutron stars across a wide range of settings -- from the cold, equilibrium conditions of an isolated neutron star, to the hot and dynamical environment following a merger. In this talk, I will discuss a framework for connecting astrophysical observations of neutron stars to the microphysics of their interior structure. I will discuss what we have learned about the dense-matter equation of state from the first observations of neutron stars mergers, and what we hope to learn from current and upcoming experiments over the next decade. Along the way, I will present results from numerical simulations of neutron star mergers to highlight some of the key open questions and challenges that lie ahead.

  Bio

  Dr. Raithel is a joint postdoctoral fellow at the Institute for Advanced Study, the Princeton Center for Theoretical Science, and the Princeton Gravity Initiative. She received her PhD in Astronomy & Astrophysics from the University of Arizona in 2020. Dr.  Raithel is interested in using the astrophysical properties of neutron stars to study the dense-matter equation of state. She uses a variety of analytical techniques as well as numerical simulations to understand the mapping between neutron star observables and the underlying physics of the stellar interior. Recently, she has been particularly interested in studying the gravitational wave signatures of neutron star mergers which are now being observed by the LIGO/VIRGO collaboration. By simulating neutron star mergers in numerical relativity and with realistic finite-temperature microphysics, she hopes to uncover new insights into the properties and interactions of ultra-dense matter.

   

  February 9, 2023

  Prof. Stephen M. Wu, University of Rochester

  Strain engineering 2D quantum materials

  Abstract

  Strain engineering in electronics has been widely utilized over the last 20 years to enhance carrier mobility in most standard Si-based CMOS fabrication processes. These process-induced strain engineering techniques, engineered from the nanofabrication process itself, are simple, reliable, applied device-to-device, and highly scalable down to the nanometer scale. In this talk, I will introduce our groups work in exploring how process-induced strain engineering translates to the world of 2D materials, and how this may be applied to engineer quantum materials properties. Control over the strain degree-of-freedom in 2D materials opens new pathways for exploration in engineered quantum materials, since strain in weakly-bonded 2D systems can go far beyond strain-engineering in conventional 3D-bonded materials. This will be discussed in the context of three different ongoing projects in our group: 2D straintronic phase-change transistors/memristors, moiré superlattice engineering with strain in twisted bilayer 2D heterostructures, and strain-controllable edge state superconductivity in 2D topological Weyl semimetals.

   

  January 12, 2023

  Prof. John Lajoie, Iowa State University

  The ELectron Ion Collider: A Unique New Microscope for Matter

  Abstract

  The visible world around us is made up of atoms, with protons and neutrons forming the nuclei at their core. Together, protons and neutrons make up most of the mass of everything we see in the universe today, from massive galaxies to individual people. Protons and neutrons themselves are complicated many-body quantum states whose properties are determined by the quarks and gluons that they are comprised of. The quest to understand in detail the structure of protons, neutrons, and nuclei is nothing less that an attempt to answer the questions "What are we made of? What is matter?" The Electron Ion Collider (EIC), to be built by JLab and BNL, will be a unique new machine to collide polarized electrons off polarized protons and light nuclei, providing the capability to study multi-dimensional tomographic images of protons and nuclei, and collective effects of gluons in nuclei. In this colloquium I will motivate the physics program at the EIC and the unique new machine and detectors that will be required to answer these fundamental questions.

  Bio

  John Lajoie is the Harmon-Ye Professor of Physics at Iowa State University. His research interests include fundamental QCD, understanding the detailed properties of the Quark-Gluon Plasma, and the structure of hadrons and nuclei. He was the Level-2 manager for construction of the sPHENIX hadronic calorimeters, and currently serves on the Steering Committee for ePIC, the first detector to be built at the future Electron Ion Collider (EIC).

• Fall 2022

  December 15, 2022

  Prof. Anthony Timmins, University of Houston, Texas

  10+ years of Heavy-Ion Physics at the Large Hadron Collider

  Abstract

  The ALICE experiment was proposed in 1993, to study strongly interacting matter at extreme energy densities via a comprehensive investigation of nuclear collisions at the LHC. Its physics program initially focused on the determination of the properties of the Quark-Gluon Plasma (QGP), a deconfined state of quarks and gluons. It is speculated that the early Universe existed in such a state micro seconds after the Big Bang. The physics program was extended along the years to cover a diverse ensemble of observables related to Quantum Chromodynamics (QCD), the theory of strong interactions. The experiment has studied Pb-Pb, Xe-Xe, p-Pb and pp collisions in the multi-TeV energy range, during the Run 1 and Run 2 data taking periods at the LHC (2009-2018). The ALICE collaboration has just released a review article, that documents its major findings during this period. I will present a summary of this article.

  Bio

  Dr. Anthony Timmins is a proud Wayne State Alumni. He attained his PhD in 2008 from the University of Birmingham, (UK). His thesis topic centered around studies of strangeness enhancement in Cu+Cu collisions at the STAR experiment, located at the BNL RHIC. He was a postdoc at Wayne State between 2008-2010, where he worked in the Relativistic Heavy-Ion Group. He then moved to the University of Houston in 2010, where he is now an Associate Professor. His present day research mainly focuses on the ALICE experiment at the CERN LHC. He is currently the coordinator of the ALICE-USA collaboration, of which both Wayne State and the University of Houston are members.

   

  December 8, 2022

  Prof. Joey Rodriguez, Michigan State University

  Understanding Planetary Evolution with TESS

  Abstract

  The success of transit and RV surveys have shifted the exoplanet field from pure discovery to a combination of discovery, demographic analysis, and detailed characterization, especially for exoplanet atmospheres. However, even with nearly 5000 exoplanets known, we are still working to understand their origins and evolutionary mechanisms. Using data from NASA’s TESS and Kepler/K2 missions, we are working to find keystone planetary systems around bright stars (those well suited for atmospheric observations) that can help address specific questions about planet formation and evolution. Additionally, many of the known transiting planets to date have ephemerides that have degraded to uncertainties of many hours, making them inaccessible in the era of JWST. I will review our efforts to discover and characterize new exoplanet systems from TESS and provide the community with updated ephemerides and system parameters for future atmospheric characterization and population studies.

  Bio

  Joey Rodriguez is an assistant professor in the Department of Physics and Astronomy at Michigan State University. He received his Ph.D. from Vanderbilt University for using transiting exoplanets and eclipsing disks to understand planet formation and evolution. Prior to his appointment at MSU, he was a Future Faculty Leaders Postdoctoral fellow and a Smithsonian Astrophysical Observatory Astronomer working at the Center for Astrophysics | Harvard & Smithsonian. Currently, his focus is discovering new keystone exoplanetary systems that provide insight into key questions about planet formation/evolution using observations from NASA’s Kepler, K2, and TESS missions.

   

  December 1, 2022

  Prof. Christopher V Kelly, Wayne State University

  Nanoscale membrane curvature, lipid phases, molecular sorting, and single-molecule diffusion

  Abstract

  Cellular homeostasis requires the precise spatial and temporal control of membrane shape and composition. However, the nanoscopic interdependence of membrane properties is difficult to observe and poorly understood. We developed and employed model samples, fluorescence microscopy methods, and computational simulations to observe single-molecule behavior with varying membrane composition, phase, temperature, and shape. For example, engineered, hemispherical membrane buds induced lateral compositional heterogeneity in otherwise homogeneous membranes. The curvature-induced sorting of lipid phases was quantified by the sorting of disorder-preferring fluorescent lipids, single-lipid diffusion measurements, and simulations that couple the lipid phase separation to the membrane shape. Unlike single-component membranes, lipids in phase-separated membranes demonstrated faster diffusion on curved membranes than the surrounding, flat membrane. These results support the hypothesis that the coupling of lipid phases and membrane shape couple to yield lateral membrane composition heterogeneities with functional consequences.

  Bio

  Dr. Christopher V. Kelly joined the Department of Physics and Astronomy at Wayne State University in 2013. Prior to moving to Detroit, Michigan, Dr. Kelly was a postdoctoral fellow at Cornell University with a Kirschstein-NRSA NIH postdoctoral fellowship. Dr. Kelly earned his B.A. from Oberlin College in Physics, his M.S.E. in Electrical Engineering from the University of Michigan, and his Ph.D. in Applied Physics from the University of Michigan. Dr. Kelly is finishing his NSF CAREER Award focused on curvature in membrane bilayers and beginning his R01 grant from the NIDDK focused on the biophysics of membrane monolayers surrounding lipid droplets. He is the director of the Richard Barber Interdisciplinary Research Program, which provides research opportunities to undergraduate students across WSU in interdepartmental research projects. His expertise includes nanoscopic optics, nanoengineering, and computational techniques to resolve the underlying biophysical principles that govern biological membranes.

   

  October 27, 2022

  Dr. Meenakshi Narain, Brown University

  The CMS Experiment

   

  October 25, 2022

  Prof. Gil Paz, Wayne State University

   

  October 20, 2022

  Prof. Wolfgang Schleich,  Institut für Quantenphysik and Center for Integrated Quantum Science and Technology, Universität Ulm, Germany

  Capitalizing on Schrödinger

  Abstract

  The superposition principle is a cornerstone of quantum mechanics and results from the linearity of the Schrödinger equation. In this talk we motivate the non-linear wave equation of classical statistical mechanics as well as the linear Schrödinger equation of quantum mechanics from a mathematical identity. Moreover, the linearity is crucial for the use of matter wave interferometers as sensors for rotation and acceleration. We show that the phase in a Kasevich-Chu atom interferometer measures the commutator of two unitary time evolutions and thus the acceleration. In addition, we report the observation of the Kennard phase using water waves and the realization of a Kennard interferometer with a scaling superior to the Kasevich-Chu interferometer.

   

  October 13, 2022

  Prof. Nestor Espinoza, Johns Hopkins University

  From first galaxies to the atmospheres of Earth-sized worlds: a New Era of Astronomy with the James Webb Space Telescope

  Abstract

  The recently commissioned James Webb Space Telescope (JWST) is set to become humanity's sharpest eye to look at the infrared Universe. From being able to detect the faint light of the first galaxies to being able to characterize the atmospheres of Earth-sized worlds, the observatory's unique capabilities will allow it to perform a wide range of exciting science, that will undoubtedly revolutionize our understanding of the Universe. In this talk, I will introduce the JWST from both a technological and a scientific perspective, sharing a few of the most exciting science cases the observatory will perform during its first year of scientific observations, along with its very first results. Special emphasis will be given to the exoplanet science the observatory will perform, which will dramatically change our understanding of planetary systems in the cosmos, allowing us to put our own Solar System in this exoplanetary context.

   

  October 6, 2022

  Prof. Chun Shen, Wayne State University

  Flowing through the nuclear phase diagram at the highest temperatures and densities

  Abstract

  Nuclear matter has a complex phase structure, ​including a deconfined Quark-Gluon Plasma (QGP) phase ​at extreme pressures and temperatures. The hot QGP behaves like an inviscid fluid and filled the universe during its first few microseconds after the Big Bang. High energy collisions of heavy atomic nuclei recreate this hot nuclear matter in the laboratory. In this talk, I will review recent theoretical progress in studying the QGP transport properties. The Relativistic Heavy-Ion Collider (RHIC) has conducted a beam energy scan whose results offer a unique opportunity to study the nuclear phase diagram in a baryon-rich environment. I will highlight the development of a comprehensive framework that can connect the fundamental theory of strong interactions with the RHIC experimental observables. This dynamical framework paves the way for quantitative QGP characterization and locating the critical point in the nuclear phase diagram. These studies will advance our understanding of strongly interacting many-body systems, building interconnections with other areas of physics, including neutron star mergers, string theory, cosmology, and cold atomic gases.

  Bio

  Prof. Shen got his Ph. D degree from the Ohio State University in 2014. After graduation, he was a postdoc fellow at McGill University and a Goldhaber Fellow at the Brookhaven National Laboratory. He accepted a RIKEN-BNL bridged position as an assistant professor at Wayne State University in 2018. Over the years, he received the 2016 APS dissertation award in nuclear physics and the IUPAP young scientist prize in nuclear physics in 2019. In 2021, he was awarded the DoE Early Career Award.

   

  September 29, 2022

  Prof. Alex Matos Abiague, Wayne State University

  Topological Superconductivity in Planar Josephson Junctions

  Abstract

  Topological superconductivity (TS) is a phase of matter supporting the formation of quasiparticles called Majorana bound states, which can store information nonlocally and are therefore ideal candidates for building robust qubits with potential applications in fault-tolerant quantum computing. Planar Josephson junctions (JJs) have recently emerged as promising platforms for realizing and manipulating the TS state. However, despite the recent progress, important questions regarding the properties, signatures, and detection of TS remain open. In this talk, I will discuss the relevance and limitations of recent experimental results and propose new effects (e.g., magneto and crystalline anisotropies) that can provide complementary signatures of the transition into the TS state and be used as control knobs for optimizing the topological protection of Majorana bound states. Our theoretical predictions indicate that quantities like critical current, spin susceptibility, and/or magneto current-phase relation, can be used to map the topological phase diagram, providing a more complete picture of the TS state. I will also discuss recently proposed platforms for realizing, manipulating, and detecting topological qubits in planar JJs.

   

  September 22, 2022

  Prof. Igor Mazin, George Mason University

  Conventional high temperature superconductivity: from A15 to MgB2 to superhydrates

  Abstract

  I will review in a rather popular-science way, mostly for the benefits of the younger generation, the history of the half-century long quest for room-temperature superconductivity, concentrating on the

  conventional electron-phonon mechanism. I will outline several stages, characterized by different paradigms, which can be tagged in a Potterianway thus:
  (1) A-15 and the concept of an upper bound on Tc

  (2) V.L. Ginzburg and the concept of a negative dielectric function

  (3) MgB2 and the concept of doped covalent bonds

  (4) H3S and the concept of MgB2 on steroids

  (5) Superhydrates and the concept of artificially stabilized metal hydrogen

   

  September 20, 2022

  Prof. Jian Huang, Wayne State University

  Topological protection probed by real-time bulk and edge measurement.

  Abstract

  Quantum properties associated with topology are unchanged in response to a specific range of variations in the system. This range marks topological robustness that, in real systems (such as quantum Hall and quantum spin Hall effects), varies substantially and may even break down in the presence of small disturbances. Investigations of effects influencing topological protection have revealed complicated electron behaviors centered around the notion of topological robustness against disorders (i.e. in graphene). However, the question of what makes a topological order more or less robust is not sufficiently addressed by separate studies of the edge states and the bulk states alone. In this study, with an integer quantum Hall effect (IQHE) hosted in a Corbino two-dimensional system brought to the verge of a topological breakdown, simultaneous measurements of the bulk and edge responses are carried out independently to accurately measure both insulating and conducting behaviors. The source of the topological breakdown is identified as back-scatterings between dissipationless current paths of opposite chirality facilitated by local resonant tunneling. It is captured in real-time correspondence with the emergence of edge dissipation and deviation from Hall quantization. The unique “staircase” features characterizing the breakdown prompt a specific global reconstruction. The enhancement of the bulk localization marks an important contribution from electron-electron interaction that enhances topological robustness through impurity screening. The variations in topological robustness are thus understood as a disorder-interaction interplay. The technique is useful for studying bulk-boundary correspondence (BBC) in various topological quantum matters.

   

  September 15, 2022

  Dr. Simon Michaux, Geological Survey of Finland (GTK)

  Quantity of metals required to manufacture one generation of renewable technology to completely phase out fossil fuels.

  Abstract

  A study was conducted to examine what is going to be required to fully phase out fossil fuels as an energy source and replace the entire existing system with renewable energy sources and transportation. This is done by estimating what it would be required to replace the entire fossil fuel system in 2018, for the US, Europe, China, and global economies. This report examines the size and scope of the existing transport fleet, and complete scope of fossil fuel industrial actions (electricity generation, heating, steel manufacture, EV battery charging, and hydrogen production for H-Cells). To replace fossil fueled ICE vehicles, Electric Vehicles, H2 cell vehicles for cars, trucks, rail, and maritime shipping was examined. Fossil fuels consumption for electricity generation, building heating and production of steel were all examined for replacement. Calculations reported here suggest that the total additional non-fossil fuel electrical power annual capacity to be added to the global grid will need to be around 37 006.9 TWh. To phase out fossil fuel power generation, solar, wind, hydro, biomass, geothermal and nuclear were all examined, and were part of the calculations.An estimated of the possible 2050 non-fossil fuel energy mix was developed from IRENA 2022 and Michaux 2021. Given this, then an extra 586 032 new average sized power plants will be needed to be constructed and commissioned.

  The quantity of metals to manufacture one generation of renewable technology (EV’s, batteries, H-cells, wind turbines, solar panels, etc.) was estimated using the numbers assembled. This quantity of metal was compared to 2019 global mining production and 2022 global mineral reserves. Conclusions were drawn. It was proposed that the phasing out of fossil fuels will not go to plan.

   

• Winter 2022

  April 21, 2022

  Prof. Ian Low, Northwestern University

  The Future Frontier of Higgs Physics

  Abstract

  The Higgs boson was discovered in 2012 at the Large Hadron Collider in Switzerland and hailed as the origin of mass. I will summarize our current understanding, as well as ignorance, of the Higgs boson. In particular, I will explain why the Higgs boson represents the most exotic state of matter to have been observed in Nature. Then I will conclude with directions for future explorations.

   

  April 7, 2022

  Prof. Xiangdong Ji, University of Maryland

  Exposing the hidden glue of the mundane world

  Abstract

  Gluons in the low-energy strong-interaction world dominate everything, but there is no hard evidence. The potentially-detectable glues are confined to a small region of space of order one fermi, and are completely blind to electromagnetism and weak interactions. However, they contribute significantly to the momentum, mass, spin, and other properties of the protons and neutrons---the dominant matter component in our visible universe. In this talk, I will discuss how to expose them through special processes in electron scattering on nucleons and nuclei at JLab and future EIC. I will also describe theoretical efforts to compute their effects through large-scale lattice QCD simulations.

   

  March 24, 2022

  Prof. Ahmet Yildiz, University of California Berkeley

  The Mechanism and Regulation of Microtubule Motors

  Abstract

  Kinesin and dynein motors hydrolyze the energy of ATP hydrolysis to walk on microtubule filaments and carry a wide variety of cargos to many destinations inside cells. To understand the mechanism of their action, we developed methods to track the movement of a single motor at nanometer resolution in real-time.  Using these methods, we presented a robust mechanistic model of how dynein takes steps, moves towards the minus-end of microtubules, and generates force. I will also discuss how kinesin and dynein are recruited to mitochondria and their motility is regulated by accessory proteins to control bidirectional transport.

  Bio

  Ahmet Yildiz received his Ph.D. in biophysics at the University of Illinois at urbana champaign (UIUC), where he developed a single fluorescent particle tracking method with one-nanometer accuracy with Prof. Paul Selvin and showed how molecular motors of cytoskeleton walk along linear tracks inside cells. He completed his postdoctoral work with Prof. Ron Vale at the University of California San Francisco as a Jane Coffin Childs, and Burroughs Welcome Fellow. His work in single molecule fluorescence has been awarded Gregory Weber International Prize in Biological Fluorescence in 2005 and the Young Scientist Award by Science Magazine in 2006. In 2008, he joined Physics and MCB departments at UC Berkeley. His research group develops biophysical approaches to study fundamental biological processes, such as intracellular cargo transport, and the replication of telomeres at a single molecule level. His research has been recognized with the NSF CAREER Award, Presidential Early Career Award, Sloan Fellowship, EMF Young Investigator Award, ASCB Emerging Leader Prize, Michael and Kate Barany Award by BPS, and the Vilcek Prize.

   

  March 17, 2022

  Prof. Chanda Prescod-Weinstein, University of New Hampshire

   

  February 10, 2022

  Prof. Alexey Kovalev, University of Nebraska-Lincoln

  Towards control of spin currents in magnetic insulators

  Abstract

  An ability to control spin currents is important for probing many spin related phenomena in the field of spintronics and for designing logic and memory devices with low dissipation. Spin-orbit torque is an important example in which spin current flows across magnetic interface and helps to control magnetization dynamics. As spin can be carried by electrons, spin-triplet pairs, Bogoliubov quasiparticles, magnons, spin superfluids, spinons, etc., studies of spin currents can have implications across many disciplines. In this talk, I will first discuss transport, Hall-like responses of magnons in antiferromagnetic insulators, ranging from collinear antiferromagnets to breathing pyrochlore noncollinear antiferromagnets. The theory also applies to noncollinear antiferromagnets, such as kagome, where we predict both the spin Nernst response and the generation of nonequilibrium spin polarization by temperature gradients, the latter effect constitutes the magnonic analogue of the Edelstein effect of electrons. I will further discuss the spin superfluid transport associated with collective modes in magnetic insulators. We observe that in two dimensional systems at finite temperatures spin superfluidity is affected by the presence of topological defects. We further propose to use the Hall response of topological defects, such as merons and antimerons, to spin currents in 2D magnetic insulator with in-plane anisotropy for identification of the Berezinskii-Kosterlitz-Thouless (BKT) transition in a transistor-like geometry. Our numerical results relying on a combination of Monte Carlo and spin dynamics simulations show transition from spin superfluidity to conventional spin transport, accompanied by the universal jump of the spin stiffness and exponential growth of the transverse vorticity current. We propose a superfluid spin transistor in which the spin and vorticity currents are modulated by tuning the in-plane magnet across BKT transition, e.g., by changing the exchange interaction, magnetic anisotropy, or temperature.

  Bio

  Prof. Kovalev is a theoretical condensed matter physicist working on theoretical spintronics that comprises various classical and quantum phenomena related to the spin degree of freedom. Prof. Kovalev was appointed as an Assistant Professor at Department of Physics and Astronomy, the University of Nebraska-Lincoln in 2013, and promoted to an Associate Professor in 2019. He received his Master of Science in Physics from Moscow Institute of Physics & Technology, Russia. He has received his Ph.D. degree in Physics from Delft University of Technology in 2006. Prof. Kovalev worked as a research associate (Post-Doc) in between 2006 and 2008 at Texas A&M University, and in between 2008 and 2010 at UCLA. He has received Nebraska EPSCoR First Award at 2014 and DOE Early Career Award at 2015.

   

  January 20, 2022

  Prof. Ajay Gopinathan, University of California, Merced

  Frustration Drives Flocks of Cancer Cells

  Abstract

  Flocks of birds and schools of fish are delightful and awe-inspiring examples of collective motion that we see in nature, where groups of individuals, each possessing only limited, local information, nevertheless come together and display coordinated motion. This phenomenon also extends to much smaller scales, as in migrating clusters of cells that mediate physiological processes such as embryonic development, wound healing, and cancer metastasis. The collective, co-ordinated motion of cells allows for emergent behaviors unavailable to single cells that are critical for proper function. In this talk, I shall describe our work on modeling such phenomena in cancer cell clusters, highlighting how frustration can arise at the group level because of heterogeneity in behavior among individual cells in the cluster. I shall show how this frustration can be resolved leading to new collective phases of motion that are experimentally observed in malignant lymphocyte clusters and functionally important – enabling robust chemotaxis and “load sharing” among cells.

  Bio

  Professor Gopinathan is a Professor and currently Chair of the Department of Physics at the University of California, Merced (UCM). He is also a Director of the NIH-funded G-RISE (T32) graduate training program and of the NSF-funded CREST Center for Cellular and Biomolecular Machines (CCBM) at UCM. His educational background includes an integrated Masters in Physics from the Indian Institute of Technology, Kanpur. He obtained his Ph.D. in Physics from the University of Chicago, working on various soft condensed matter systems including sheets, colloids, and polymers, followed by a postdoctoral stint at UCLA and UCSB working on protein biopolymer dynamics. He then joined UCM, a brand new research university that had just opened, as one of the first physicists on campus. His group uses theoretical and computational methods to explore the basic physics underlying a variety of biological transport processes ranging in scale from molecular motor transport to the collective motility of cells and organisms. He is a recipient of the 21st Century Science Initiative Award from the James S. McDonnell Foundation, a Scialog Fellowship from the Moore Foundation and Research Corporation, and the George E. Brown Award from UC MEXUS. He was recently elected a Fellow of the American Physical Society (APS) and to the Chair line of the Division of Biological Physics (DBIO) of the APS.

   

  January 13, 2022

  Prof. Elke-Caroline Aschenauer, Brookhaven National Laboratory

  The electron-ion collider: A world-wide unique collider to unravel the mysteries of visible matter

  Abstract

  Understanding the properties of nuclear matter and its emergence through the underlying partonic structure and dynamics of quarks and gluons requires a new experimental facility in hadronic physics known as the Electron-Ion Collider (EIC). The EIC will address some of the most profound questions concerning the emergence of nuclear properties by precisely imaging gluons and quarks inside protons and nuclei such as their distributions in space and momentum, their role in building the nucleon spin and the properties of gluons in nuclei at high energies. In January 2020 the EIC received CD-0 and Brookhaven National Laboratory was selected as site, and June 2021 CD-1 was granted to the EIC Project. This presentation will highlight the science capabilities of the EIC, discuss its accelerator design and the concepts for the detectors and give the status of the EIC project.

   

   

   

• Fall 2021

  December 9, 2021

  Prof. Tudor Stanescu, Department of Physics and Astronomy, West Virginia University

  The quest for the topological qubit: navigating the sea of disorder

  Abstract

  Topological quantum computing is the most elegant way of achieving robust quantum computation. A promising proposal for realizing topological qubits involves Majorana zero modes – quasiparticles with non-Abelian fractional statistics that emerge in certain types of superconductors. In the past ten years, significant progress toward the realization of Majorana zero modes has been made using different types of solid-state systems, particularly proximity-coupled semiconductor-superconductor hybrid structures. Yet, serious challenges still remain. The most significant problem stems from the presence of disorder generated by the fabrication process and by materials that are not clean enough. In this talk, I will sketch the main ideas behind topological quantum computing and Majorana-based topological qubits and emphasize the importance of understanding the role of disorder and minimizing its effects.

  Bio

  Prof. Stanescu is a theoretical Condensed matter physicist working on topological insulators and superconductors, topological quantum computation, ultra-cold atom systems in optical lattices, and strongly correlated materials. Prof. Stanescu was appointed as an Assistant Professor at the Department of Physics, West Virginia University in 2009, and promoted to an Associate Professor in 2015 and to a Full Professor in 2020. He received his Master of Science in Physics (1991) at the University of Bucharest (Romania) and also in 1997 at the University of Illinois at Urbana-Champaign. He has received his Ph.D. degree in Physics, the University of Illinois at Urbana-Champaign. Prof. Stanescu worked at several different places as a research associate between 2002 and 2009. He wrote his book in 2017 as a title of Introduction to Topological Quantum Matter & Quantum Computation, CRC Press, Taylor & Francis Group.

   

  December 2, 2021

  Prof. Thomas Schaefer, Department of Physics, North Carolina State University

  From cold atoms to nuclei and neutron stars

  Abstract

  Progress in atomic physics has enabled the experimental realization of a "Unitary Fermi Gas". This is a system of non-relativistic spin 1/2 fermions interacting via a potential tuned to zero range but infinite scattering length. The emergent quantum many body system is a scale invariant, strongly correlated quantum fluid. It is linked, by universality, to other systems in nature, in particular the neutron liquid that forms the outer layer of a neutron star. We will explain how studies of the unitary gas inform our understanding of  the equation of state of neutron matter, short range correlations in nuclei, and the transport properties of nuclear matter.

  Bio

  Thomas Schaefer is the Wesley O. Doggett Distinguished Professor of Physics at North Carolina State University, a member of the Nuclear Theory Group at North Carolina State, and a former fellow at the RIKEN-BNL Research Center. He received his bachelor’s in physics at the University of Giessen in 1989 and his Ph.D. from the University of Regensburg in 1992. His work is focused on QCD, many body effects in atomic, nuclear, and particle physics, as well as transport theory. From 1998-1999 he was a member of the Institute for Advanced Study in Princeton before joining the faculty at Stony Brook University as an assistant professor in 2000. He was promoted to the rank of associate professor in 2003 and joined the faculty of North Carolina State University the same year. He was promoted to full professor in 2006. From 2000-2004, he was also a fellow at the Riken-BNL research center at BNL. Dr. Schaefer received a Fedor Lynen Fellowship from the Alexander von Humboldt Foundation in 1992, an Outstanding Junior Investigator Award from DOE in 2002, and was elected a fellow of the APS in 2006. He served as an Associate Editor of Physical Review Letter, as a member of the National Academies Study of US-based Electron-Ion Collider Science, and as a member of NSAC, the Nuclear Science Advisory Committee. He is currently the Nuclear Physics Editor for Reviews of Modern Physics.

   

  November 4, 2021

  Prof. Pavel Kovtun, Department of Physics and Astronomy, University of Victoria, Canada

  Hydrodynamics beyond hydrodynamics

  Abstract

  Hydrodynamics is a well-established field with a venerable history. In this talk, I will focus on foundational aspects of hydrodynamics which came to light in recent years. Do the equations of hydrodynamics even make sense? To what degree can the crudeness of hydrodynamics be improved? What about the phenomena that hydrodynamics should describe but fails to? And what about the phenomena that hydrodynamics shouldn't describe, but does?

  Bio

  Pavel Kovtun is a theoretical physicist working at the University of Victoria, Canada. Pavel did his undergraduate degree in Kharkiv, Ukraine, and received his PhD from the University of Washington (Seattle) in 2004. He was a postdoctoral fellow at the Kavli Institute for Theoretical Physics (Santa Barbara) before joining the University of Victoria in 2007 where he is now professor. Pavel has worked on quantum and statistical field theory, and applied string theory. His most well-known work relates to the universal properties of viscosity in strongly interacting quantum fluids, through the connections between fluid mechanics and black hole physics. More recently, he has been interested in foundational questions in the hydrodynamics of relativistic fluids.

   

  October 28, 2021

  Prof. Ashis Mukhopadhyey, Department of Physics and Astronomy, Wayne State University

  Slippery when Wet: How tiny particles move through complex environment

  Abstract

  During the 'miracle year' of 1905, Einstein also completed his thesis and wrote two papers on the topic of Brownian motion. Combined with Stoke's law, his theory can explain very well the random erratic movements of suspended particles within the water or any fluids. The Stokes-Einstein (SE) theory, however, has important limitations, which are often forgotten. With carefully selected systems, I will demonstrate that there is a ‘goldilocks’ zone, where the common wisdom break down and tiny particles can slip through fluids a thousand times faster compared to the prediction of SE theory. The results have ramification in understanding of intracellular transport, navigation of viruses through mucus, and development of self-healing plastics.s

  Bio

  Dr. Mukhopadhyay is an experimental soft matter physicist working in the areas of colloids and polymers. He earned his Ph.D. from Kansas State University in 2000 on the topic of surface critical phenomena. He did postdoctoral research on confined fluids from the University of Illinois, Urbana Champaign from 2000 through 2003. He joined Wayne State University as an Assistant Professor in 2003 and was promoted to Associate professor with tenure in 2008. He has a guest appointment at Max Planck Institutes and the University of Michigan.

   

  October 21, 2021

  Prof. Joern Putschke, Department of Physics and Astronomy, Wayne State University

  Exploring Hot-QCD Matter Properties with Jets

  Abstract

  I will discuss recent progress of jet sub-structure measurements in proton-proton and in heavy-ion collisions which can provide crucial information about the mechanism of jet quenching in the hot and dense QCD medium created in these collisions and about its properties over a wide range of distance scales. The emphasis in this talk will be on measurements at RHIC energies with the STAR detector and how these measurements will inform the jet program at the future dedicated jet experiment sPHENIX, currently under construction and expected to take data in 2023.  

  Bio

  Ph.D. Max-Planck-Institute (Munich) in 2004, elliptic flow and particle multiplicities at forwarding rapidities in d+Au and Au+Au with the Forward-TPC’s in STAR. Postdoc LBL and Yale (2005-2011), the discovery of what is now commonly referred to as the (high-pT) “ridge” in Au+Au collisions, first jet measurements in STAR (STAR jet working group convener) and ALICE-USA EMCal jet working group coordinator (CDR, TDR, and PPR). Since 2011 faculty (Assoc. Prof.) at Wayne State University (ALICE jet working group convener, 2015-2017). My group performed jet and di-jet measurements in pPb and the first jet mass measurement in pPb and PbPb in ALICE, as well as the first Au+Au Di-Jet imbalance and jet splitting function measurement at RHIC in STAR. Member of the sPhenix collaboration and Co-PI of the JETSCAPE/XSCAPE (Theory and Experiment) collaboration (lead software designer of the JetScape framework). Member of the community White Paper writing committee(s) (“Hot and Dense QCD Matter” and “The Hot QCD White Paper: Exploring the Phases of QCD at RHIC and the LHC”). The organizer of the jet and heavy-flavor INT program in 2017, QM 2017, and various (jet) workshops at Wayne State, AGS Users Meeting(s), and RBRC.

   

  October 14, 2021

  Prof. Nausheen Shah, Department of Physics and Astronomy, Wayne State University

  The Naturally Unnatural Standard Model of Particle Physics

  Abstract

  The Standard Model (SM) of Particle Physics provides an excellent description of nature. However, it is very much an empirical model: Why are there 3 generations of matter with such large mass hierarchies? What is the origin of their mixings? What is dark matter (DM)? What dynamics govern the Higgs mechanism? If Ultraviolet symmetry breaking governs the structure we observe at the weak scale, apparent fine-tunings may be a hint of the global structure dictating beyond the SM physics. In this talk, I will discuss some fine-tunings that may be responsible for the structure we observe in Higgs couplings, fermion masses, and mixings, and possible connections of the Higgs sector with DM.

  Bio

  Prof. Nausheen Shah is a theoretical physicist working on understanding the basic principles underlying the observed structure of the universe. In particular, she is currently studying how the Higgs boson and Dark Matter can shed light on the presence of new physics beyond the Standard Model of physics, using the interplay between high energy physics theory, experiment, and cosmology. Shah received her Ph.D. in theoretical particle physics from the University of Chicago. She was a postdoctoral fellow at Fermilab and the University of Michigan before joining the faculty at Wayne State University in 2015.

  Presentation video

   

  September 30, 2021

  Prof. Edward Cackett, Department of Physics and Astronomy, Wayne State University

  Mapping the accretion disk around supermassive black holes

  Abstract

  Every major galaxy seems to contain a supermassive black hole at its center. About 1% of these supermassive black holes are actively accreting gas from surrounding material and are referred to as Active Galactic Nuclei (or AGNs).  The gravitational potential energy liberated as this gas sinks towards the black hole (‘accretes’) make AGNs some of the most luminous objects in the Universe. Accretion is an important process since the energy that feeds back into the host galaxy has an important influence on its evolution. Accretion is thought to take place via an optically thick, geometrically thin ‘accretion disk’. However, the angular size of these disks is too small to be resolved with current technology. I will describe how we use a technique called reverberation mapping, which swaps spatial resolution for time resolution, to infer the size of these accretion disks and better understand what happens in the region closest to the supermassive black hole in AGNs. 

  Bio

  Prof. Cackett was appointed as an Assistant Professor here in the Department of Physics and Astronomy at Wayne State University in January 2012 and promoted to Associate Professor in August 2016.  Prof. Cackett’s research interests are broadly observational studies of the astrophysics of black holes and neutron stars.  He received his Master of Science in Physics (2003) from the University of Durham in the U.K., and his Ph.D. degree (2007) in Physics from the University of St. Andrews, UK. Before joining WSU, he was a postdoctoral research fellow at the University of Michigan (2006-2010), where he was a prestigious NASA Chandra Fellow, and at the University of Cambridge (2010-2011). Prof. Cackett was the recipient of a National Science Foundation (NSF) CAREER award in 2014.  He has received several awards at WSU including the WSU Career Development Chair (2017), WSU Department of Physics and Astronomy Richard J. Barber Faculty Recognition Award (2017), Wayne State Academy of Scholars, Junior Faculty Award (2015), & Sultana N. Nahar Prize for Distinction in Research in Physic and Astronomy (2019).

• Winter 2021

  April 8, 2021

  Prof. Eric Weeks, Department of Physics, Emory University

  Flowing and clogging of soft particles and droplets

  Abstract

  We study the flow and clogging of soft particles: micron-sized oil droplets, centimeter-sized hydrogel particles, and simulated soft particles.  We find that softness is a key factor controlling clogging:  with stiffer particles or a weaker driving force, clogging is easier.  Softer particles form less stable arches and thus reduce the probability of clogging.  Our results suggest that prior studies using hard particles were in a limit where the role of softness is negligible, which causes clogging to occur with significantly larger openings.  In addition to softness, we also have some understanding of the roles of friction, vibrations, hydrostatic pressure, viscosity, and geometry… there’s a lot of physics behind clogging!

  Bio

  Eric Weeks earned his undergraduate degree in engineering physics at the University of Illinois at Urbana-Champaign. In 1997 he graduated with a Ph.D. in physics from the University of Texas at Austin, working in the Center for Nonlinear Dynamics with Prof. Harry Swinney.  His dissertation was on experiments studying anomalous diffusion and atmospheric phenomena.  He started a postdoctoral fellowship at the University of Pennsylvania with Prof. David Weitz and Prof. Arjun Yodh, and finished his postdoctoral work at Harvard University when the Weitz lab moved there.  In January 2001 he joined the faculty of Emory University, where he is currently a Dobbs Professor of Physics.  Since July 2018 he has also been the Director of Emory's Center for Faculty Development and Excellence.

   

  March 25, 2021

  Prof. Mary B. James, Dean for Institutional Diversity & A.A. Knowlton Professor of Physics, Reed College

  TEAM_UP Report: The Time is Now Charting a Course to 2030 

  Abstract

  The AIP National Task Force to Elevate African American Representation in Undergraduate Physics & Astronomy (TEAM-UP) spent two years investigating the reasons for the persistent underrepresentation of African Americans in physics and astronomy and produced a report with its findings: “The Time Is Now: Systemic Changes to Increase African Americans with Bachelor’s Degrees in Physics and Astronomy.”  In this groundbreaking report, TEAM-UP uncovers long-term systemic issues within the physics and astronomy communities that contribute to the underrepresentation of African Americans in these fields and makes important, actionable recommendations for community wide efforts to reverse this trend. 

  Slides

  References

   

  March 11, 2021

  Dr. Saptarshi Das, Department of Engineering Science and Mechanics, Materials Science and Engineering, Materials Research Institute, Pennsylvania State University

  Smart Sensors and Computing Devices for Hardware Artificial Intelligence

  Abstract

  Many animals outsmart humans in sensory skills. In fact, animals can do much more than just see, smell, touch, taste, and hear. For example, octopuses possess polarized vision, bats use ultrasound to echolocate, hyper touch sensitive spiders can trace the origin of micro-vibrations and sharks can detect electric fields as weak as nanovolts per centimeter. The extraordinary sensing ability of these animals are mostly attributed to the evolutionary success of their respective and specialized sensory organs. However, less emphasis is laid on the connectivity, association, and organization of neurons inside the brainstem of these animals. What is even more humbling is the fact that the tiny brains of these animals allocate very limited neural resources in terms of area and energy for executing these high-level computations.  

  Drawing inspiration from natural intelligent sensor design, we have developed a number of solid-state biomimetic devices that provide unprecedented energy and area benefits for sensory computations. In particular, we have mimicked auditory information processing in barn owl (Nature Communications, 10, 3450, 2019), collision avoidance by locust (Nature Electronics, 2020), and subthreshold signal detection by paddlefish and cricket using stochastic resonance (Nature Communications, 2020). We have also mimicked probabilistic computing in animal brains using low-power Gaussian synapses (Nature Communications, 10, 4199, 2019) and realized a biomimetic device that can emulate neurotransmitter release in chemical synapses (ACS Nano, 11, 3, 2017). We use novel two-dimensional (2D) nano materials, nano devices, and in-memory computing architectures to demonstrate this new paradigm of sensing and computing. Our goal is to deploy theses low-power and smart biomimetic devices at remote, inaccessible, and resource constrained locations. 

  Bio

  Dr. Das was appointed as an Assistant Professor of Engineering Science and Mechanics (ESM) and member of the Materials Research Institute (MRI) and the Intercollege Graduate Degree Program in Materials Science and Engineering at Penn State University in January 2016.  He received his B.Eng. degree (2007) in Electronics and Telecommunication Engineering from Jadavpur University, India, and Ph.D. degree (2013) in Electrical and Computer Engineering from Purdue University. Before joining Penn State, he was a Postdoctoral Research Scholar (2013-2015) and Assistant Research Scientist (2015-2016) at Argonne National Laboratory (ANL). Dr. Das was the recipient of Young Investigator Award from United States Air Force Office of Scientific Research in 2017 and National Science Foundation (NSF) CAREER award in 2021. Das Research Group at Penn State leads a new multidisciplinary area of science, namely biomimetic sensing and neuromorphic computing inspired by the neurobiological architecture and neural computational algorithms found inside various animal brains allowing evolutionary success of the species.

   

  February 18, 2021

  Dr. Mark Moldwin, University of Michigan

  The STEM Academic System: Feedbacks Limiting Diversity and Driving Inequality

  Abstract

  Despite deliberate and concerted efforts over the years, the science community has not made significant progress in increasing the representation of the discipline with respect to marginalized communities (or what will be called the “new majority” community in this talk). Using a systems approach, this presentation will discuss how academic culture promotes inequality and will describe some leading practices that can be implemented at the individual, academic department, and professional community level to help create a diverse and inclusive science community.

  Slides

   

  February 11, 2021

  Prof. Lilia M. Woods, University of South Florida

  From 2D graphene to its “cousin” 3D Weyl semimetal: Casimir effects

  Abstract

  The Casimir force is a universal interaction originating from electromagnetic fluctuations between objects, however, its magnitude, sign, scaling laws, and other dependencies are strongly affected by the interacting systems and their boundaries. The expansion of the graphene family of materials by adding silicene, germanene, and stanene has created new opportunities for probing Dirac-like physics and nontrivial band topology. Due to the finite buckling and significant spin-orbit interaction in these newly added to the materials library systems, various quantum Hall phase states can be realized by applying external fields. These in turn cause Casimir force phase transitions with many unusual features, including repulsion and quantization. Weyl semimetals, considered to be 3D graphene analogs, display very different Casimir behavior despite the common Dirac-like energy spectra. While nontrivial topology may play a dominant role in graphene interactions, such effects are secondary in the Weyl semimetal Casimir forces. These materials present an excellent platform for light-matter interactions, and, in particular, to show that the universal Casimir force has non-universal dependence upon distance, sign, magnitude, and various fundamental constants.

  Bio

  Lilia M. Woods has obtained her Ph.D. in condensed matter physics from the University of Tennessee, Knoxville with Prof. Gerald D. Mahan as a Ph.D. advisor. After graduation, she was a postdoc at Oak Ridge National Lab, followed by a second postdoc at the Naval Research Lab, where she held the prestigious Director’s funded NRC Fellowship. In 2003 she became an Assistant Professor at the University of South Florida and in 2012 she was promoted to Full Professor. Lilia M. Woods has established a vigorous research program in theoretical and computational condensed matter physics, which has been continuously funded by the National Science Foundation and the Department of Energy since 2006. She has been recognized by the USF Outstanding Research Achievement Award (three times) and by the Jewell Faculty Excellence Award. She is a member of the National Academy of Inventors. She has received the International Association of Advanced Materials Medal for 2018. Lilia Woods was also elected as an APS Fellow in 2017 and an AAAS Fellow in 2019.

• Fall 2020

  December 3, 2020

  Dr. Laura Grego, Union of Concerned Scientists

  The Growing Danger of Nuclear Weapons (and how physicists can help reduce it)

  Abstract

  While nuclear weapons might sound like Cold War relics, in truth the immense risks they pose to all humanity are still very much with us. In fact, trends indicate the risks may be growing with the abandonment of arms control agreements and the development of new types of strategic weapons. Physicists have historically constructively engaged policymakers and their communities to help reduce nuclear dangers. This talk will explain the current nuclear crisis, provide feasible remedies, and introduce a new project sponsored by the American Physical Society to help physicists once again get involved.

  Bio

  Laura Grego is a senior scientist in the Global Security Program at the Union of Concerned Scientists. She focuses her analysis and advocacy on missile defense, outer space security, and nuclear weapons. She has authored or co-authored numerous papers on a range of topics, including cosmology, space security, and missile defense, and has testified before Congress and addressed the UN General Assembly and the UN Conference on Disarmament on security issues. Before joining UCS, Dr. Grego was a postdoctoral researcher at the Harvard-Smithsonian Center for Astrophysics. She earned a Ph.D. in experimental physics at the California Institute of Technology, and a BS in physics and astronomy at the University of Michigan.

   

  November 19, 2020

  Dr. Rachel Henderson, Michigan State University

  Advancing Assessment in Physics Education: Bringing Psychometrics to Physics Education Research with an Eye to Equity and Inclusion

  Abstract

  The field of Physics Education Research (PER) has made major contributions to various educational practices and materials to reform instruction in order to recruit and retain more students. However, while many research-based instructional strategies in physics have continued to advance, reform in undergraduate physics assessment has had limited space in these conversations and needs more attention. As educators, we would like to prepare our physics students for 21st-century careers. In addition to providing the robust set of skills that students are expected to have after receiving a degree in physics, the physics community seeks to increase diversity within our classrooms. Overall, to ensure all students will become successful scientists, physics departments need to be able to provide evidence to make sure that we are reaching these goals. The importance of fairness and equity in assessment for undergraduate Science, Technology, Engineering and Mathematics (STEM) education is greater than ever. In this talk, I will motivate, through my prior research experiences, the need for the next generation of physics assessments. Advancing the practices and tools of assessment in physics, so that they are valid, fair, and effective, can better provide equal educational access and better ensure success for our students.

  Bio

  Rachel earned her Bachelor of Science degree in physics from Slippery Rock University in Pennsylvania. She then went on to do her graduate work at West Virginia University where she completed her Master’s and Ph.D. in physics. A little over two years ago, she moved here to Michigan where she did her postdoc work in collaboration with Danny Caballero in the Physics Education Research Lab at Michigan State University. Rachel is currently the newest Assistant Professor in the Department of Physics and Astronomy and the CREATE for STEM Institute at MSU. She also serves as a member-at-large for the APS Topical Group on Data Science and the APS Topical Group on Physics Education Research. She was most recently nominated to serve on the American Association of Physics Teacher Physics Education Research Leadership and Organizing Council (PERLOC). In general, Rachel’s research focuses on developing and implementing inclusive and equitable assessment tools that can be used to improve learning for all students within the physics classroom.

  Zoom Recording & Audio Transcript

   

  November 12, 2020

  Dr. Valerica Raicu, University of Wisconsin-Milwaukee

  Distance- and diffusion-based methods for probing macromolecular association in living cells

  Abstract

  Fluorescence-based methods for probing the association of proteins or other biological macromolecules within living cells fall roughly within two groups. One family of methods, based on Förster Resonance Energy Transfer (FRET), probes molecular association by measuring relative distances between molecules within a complex (or oligomer) via transfer of energy from an optically excited to un-excited fluorescent tags attached to the molecules of interest. A second class of methods, generically known as Fluorescence Fluctuation Spectroscopy (FFS), probes fluctuations in fluorescence intensities from pixel to pixel in an image (i.e., in space) or from measurement to measurement (in time series) to determine whether the molecules that produced the fluctuations diffuse around as monomers, dimers, or higher-order oligomers. In this talk, I will overview contributions of my research group to the development of such methods and their application to the study of oligomerization of membrane receptors in the presence and absence of their natural or artificial ligands. Our studies aim to provide (i) biophysicists and life scientists with tools for understanding life processes, such as cellular signaling, and (ii) pharmacologists with in-cell drug screening assays for the discovery and characterization of new drugs. 

  Bio

  Valerică Raicu is a Professor in the Physics Department and affiliated faculty in the Biological Sciences Department at the University of Wisconsin-Milwaukee (UWM). Professor Raicu’s main research interests span the development of spectroscopic and micro-spectroscopic technology and applications to the study of protein-protein and cell-cell interactions. His focus over the past decade has been the investigation of G-Protein coupled receptor oligomerization in living cells and the biological role it may play. He has authored or co-authored numerous peer-reviewed articles, book chapters, and books on various topics in physics, biophysics, and bioengineering, as well as several patents in the area of optical micro-spectroscopy. He also currently serves as the Director of the UWM Small Businesses Collaboratory and Biophysical Spectroscopy Laboratory.

   

  November 5, 2020

  Dr. Kevin Pedro, Fermilab

  Coprocessors as a service to accelerate machine learning inference for particle physics

  Abstract

  New heterogeneous computing paradigms on dedicated hardware with increased parallelization offer exciting solutions with large potential gains. The growing applications of machine learning algorithms in particle physics for simulation, reconstruction, and analysis are naturally deployed on such platforms. The acceleration of machine learning inference as a web service represents a heterogeneous computing solution for particle physics experiments that requires minimal modification to the current computing model. Coprocessors deployed as an edge or cloud service for the particle physics computing model can have a higher duty cycle and are potentially much more cost-effective. Initial results with Microsoft Brainwave FPGAs and Nvidia GPUs show more than an order of magnitude reduction in inference latency and high throughput. The demonstrated performance is suitable to address the computing challenges faced by both energy frontier and intensity frontier experiments, including the HL-LHC detectors and DUNE.

  Bio

  • B.S. Physics from Rensselaer Polytechnic Institute (Daya Bay, CLIC, CMS, ATLAS)
  • Ph.D. Physics from University of Maryland (CMS)
  • Postdoc at Fermilab (CMS)
  • (now) Associate Scientist in Scientific Computing Division at Fermilab
  • Member of CMS collaboration; informally doing some computing work for DUNE
  • Interests: dark matter from hidden sectors (semi-visible jets, emerging jets, soft unclustered energy patterns), software and computing, detector simulation, machine learning

  Zoom Recording

  Slides

   

  November 4, 2020

  Dr. Abhijit Majumdar, Wayne State University

  A Framework for Precision Exploration of the Quark-Gluon Plasma

  Abstract

  Over the last several years there has been a sea change in the study of the Quark-Gluon-Plasma (QGP) produced in high-energy heavy-ion collisions. There is now a considerable amount of high statistics data in both the high and low momentum sector. Theoretical descriptions have attained a much higher level of sophistication. This has necessitated the incorporation of Bayesian inferencing methods in the comparison between theory and data. In this presentation, I will focus on the high momentum sector and outline how the theory has evolved over the last several years, into a multi-stage, multi-faceted formalism that describes the modification of QCD jets in the QGP. Particular focus will be placed on the work of the JETSCAPE Collaboration and the need for extensive event generator frameworks. I will highlight several upcoming studies and demonstrate how these provide a much more detailed picture of the QGP.

  Bio

  • BSc Physics Indian Institute of Technology at Kharagpur 1995
  • MSc Physics Indian Institute of Technology at Kharagpur 1997
  • Ph.D. in Theoretical Nuclear Physics, McGill University, 2002
  • Post doc 1: Lawrence Berkeley National Lab. 2002 - 2005
  • Post doc 2: Duke University, 2005 - 2008 
  • Visiting assistant prof: Ohio State University 2008 - 2011
  • Associate professor: Wayne State University 2011-Present, Tenured 2015

  Research

  Study of the Quark-Gluon Plasma in Relativistic Heavy-Ion Collisions, with a focus on jets and jet quenching. Recent work has been more computational and interdisciplinary (with statistics and computer science as part of the JETSCAPE Collaboration). Have been involved with the design of extensive computer simulations of heavy-ion collisions. Carried out theoretical calculations of jet quenching both using analytic techniques as well as static simulations of the QGP using Lattice QCD. 

   

  October 29, 2020

  Dr. Omer Blaes, University of California at Santa Barbara

  Magnetohydrodynamics and Convection in Accretion Disks: From Dwarf Novae to Luminous Quasars

  Abstract

  One of the most powerful sources of energy in the universe is the liberation of gravitational binding energy as plasma falls into a central object, such as a black hole.  Such accretion flows are dynamically complex, involving significant rotational support against gravity, transport of angular momentum by magnetic turbulence, and turbulent dissipation.  Unfortunately, simulations of these processes have had a checkered history of explaining observed accretion-powered sources in the universe.  In this talk, I will show how an additional complicating factor, opacity-driven convection, exerts a powerful backreaction on the dynamics of these flows and might provide an explanation for a variety of observed phenomenology in luminous accretion flows around white dwarfs and supermassive black holes.

  Bio

  After spending his formative years growing up in the UK, Omer Blaes earned his doctorate at the International School for Advanced Studies (SISSA) in Trieste, Italy.  He then did postdoctoral work at the California Institute of Technology and the Canadian Institute of Theoretical Astrophysics in Toronto. He finally joined the Physics Department faculty at the University of
  California, Santa Barbara in 1993 and has been there ever since.  He has worked on a variety of problems in theoretical high energy astrophysics, particularly on the theory of so-called accretion disks: rapidly rotating flows around black holes and other compact objects that liberate gravitational energy into energetic outflows and radiation that we observe in a variety of spectacular phenomena across the universe.

   

  October 22, 2020

  Dr. Annika Peter, Ohio State University

  Testing the nature of dark matter with galaxies

  Abstract

  The nature of dark matter is unknown.  The leading paradigm for dark matter is that it consists of at least one species of non-relativistic ("cold"), weakly interacting particles, the cold dark matter (CDM) paradigm.  One of the strongest predictions of CDM is the hierarchy of structure down to Earth-mass scales.  However, individual self-bound clumps of dark matter--"halos"--are difficult to detect directly.  Instead, we use galaxies, which grow at the centers of halos, as lampposts for these halos.  By counting galaxies, we can measure the underlying population of dark matter halos and test the nature of dark matter.  In this talk, I describe two results that seem completely at odds with each other in measuring the population of small halos.  I argue that the resolution to the problem is a better mapping between galaxies and halos.  I will show what my group is doing so far to address the problem, and what opportunities lie ahead in the wide-field surveys of the 2020s.

  Bio

  I received a Ph.D. in physics from Princeton University in 2008.  I was a Moore postdoctoral fellow at Caltech 2008-2010, and a McCue postdoctoral fellow at UC Irvine 2011-2013.  Since 2013, I have been a faculty member in the physics and astronomy departments at The Ohio State University, and a member of the CCAPP Science Board.  I received tenure in 2019.  My work straddles the line of physics and astronomy, and theory and observation: I use the tools of astronomy and astrophysics to reveal the fundamental physics of dark matter.

  Slides

   

  October 15, 2020

  Dr. Zhixian Zhou, Wayne State University

  Two-Dimensional Layered Semiconductors beyond Graphene: Electronics and Device Physics

  Abstract

  The successful isolation of two-dimensional (2D) graphene has stimulated research on a broad range of other 2D materials, among which layered transition metal dichalcogenides (TMDs) have attracted particular attention. The semiconducting members of the TMD family including MoS2, MoSe2 and WSe2 have not only demonstrated many of the "graphene-like" properties desirable for electronic applications such as a relatively high mobility, mechanical flexibility, chemical and thermal stability, and the absence of dangling bonds but also have a substantial band gap (1 ~ 2 eV depending on the material and its thickness), which is absent in 2D graphene but required for mainstream logic applications. However, a major bottleneck in electronic applications of TMDs is their tendency to form a substantial Schottky barrier with most electrode metals, which severely limits their performance. In this talk, I will discuss our recent work aiming to overcome this fundamental challenge and subsequently explore the intrinsic transport properties of TMDs.1-5 

  1. Perera, M. M.; Lin, M.-W.; Chuang, H.-J.; Chamlagain, B. P.; Wang, C.; Tan, X.; Cheng, M. M.-C.; Tománek, D.; Zhou, Z. Improved Carrier Mobility in Few-Layer MoS2 Field-Effect Transistors with Ionic-Liquid Gating. ACS Nano 2013, 7, 4449-4458. 

  2. Chuang, H.-J.; Tan, X.; Ghimire, N. J.; Perera, M. M.; Chamlagain, B.; Cheng, M. M.-C.; Yan, J.; Mandrus, D.; Tománek, D.; Zhou, Z. High Mobility WSe2 p- and n-Type Field-Effect Transistors Contacted by Highly Doped Graphene for Low-Resistance Contacts. Nano Letters 2014, 14, 3594-3601. 

  3. Chuang, H.-J.; Chamlagain, B.; Koehler, M.; Perera, M. M.; Yan, J.; Mandrus, D.; Tománek, D.; Zhou, Z. Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe2, MoS2, and MoSe2 Transistors. Nano Letters 2016, 16, 1896-1902. 

  4. Guan, J.; Chuang, H.-J.; Zhou, Z.; Tománek, D. Optimizing Charge Injection across Transition Metal Dichalcogenide Heterojunctions: Theory and Experiment. ACS Nano 2017. 

  5. Andrews, K.; Bowman, A.; Rijal, U.; Chen, P.-Y.; Zhou, Z. Improved Contacts and Device Performance in MoS2 Transistors Using a 2D Semiconductor Interlayer. ACS Nano 2020, 14, 6232-6241. 

  Bio

  Dr. Zhixian Zhou received his Ph.D. from Florida State University/National High Magnetic Field Laboratory in 2004. After working at the Oak Ridge National Laboratory as a postdoctoral research associate, he joined Wayne State University as an assistant professor in 2007 and was promoted to associate professor with tenure in 2013.

   

  October 8, 2020

  Dr. Xiaoming Wang, University of Michigan

  Topological floppy modes in aperiodic networks and a mechanical duality theorem

  Abstract

  Topological states of matter have been intensively studied in crystals, leading to fascinating phenomena such as scattering-free edge current in topological insulators. However, the power of topological protection goes well beyond ordered crystal lattices. In this talk, we explore how topology protects mechanical edge modes in messy, noncrystalline, systems. We will use disordered fiber networks and quasicrystals as our examples, to demonstrate how topological edge floppy modes can be induced in these structures by controlling their geometry. Fiber networks are ubiquitous in nature and especially important in bio-related materials. Establishing topological mechanics in fiber networks may shed light on understanding robust processes in mechanobiology. Quasicrystals show unusual orientational order with quasiperiodic translational order. We found that a bulk topological polarization can be defined for mechanics of quasicrystals that are unique to their non-crystallographic orientational symmetry. References: (1) Di Zhou, Leyou Zhang, Xiaoming Mao, “Topological Edge Floppy Modes in Disordered Fiber Networks”, Phys. Rev. Lett. 120, 068003 (2018); (2) Di Zhou, Leyou Zhang, Xiaoming Mao, “Topological Boundary Floppy Modes in Quasicrystals”, Phys. Rev. X 9, 021054 (2019).

   

  October 1, 2020

  Dr. Eric Pop, Stanford University

  Electronic, Thermal, and (Some) Unusual Applications of 2D Materials

  Abstract

  This talk will present recent highlights from our research on two-dimensional (2D) materials, including graphene, boron nitride (h-BN), and transition metal dichalcogenides (TMDs). Our results span from material growth and fundamental measurements to simulations, devices, and system-oriented applications. We have grown monolayer 2D semiconductors over large areas, including MoS2 [1], WSe2, and MoSe2 [2]. We also uncovered that ZrSe2 and HfSe2 have native high-κ dielectrics ZrO2 and HfO2, which are of key technological relevance [3]. Improved electrical contacts [4] led to the realization of 10 nm monolayer MoS2 transistors with high current density, near ballistic limits [5]. We have also demonstrated new memory devices based on Mo-, Sb-, and Ge- tellurides [6,7]. These could all play a role in the 3D heterogeneous integration of nanoelectronics, which presents significant advantages for energy-efficient computation [8]. I will also describe a few less conventional applications, where we used 2D materials as highly efficient thermal insulators [9] and as thermal transistors [10]. These could enable control of heat in “thermal circuits” analogous with electrical circuits. Combined, these studies reveal fundamental limits and some unusual applications of 2D materials, which take advantage of their unique properties. 

  Refs: [1] K. Smithe et al., ACS Nano 11, 8456 (2017). [2] K. Smithe et al., ACS AMI 1, 572 (2018). [3] M. Mleczko et al., Science Adv. 3, e1700481 (2017). [4] C. English et al., Nano Lett. 16, 3824 (2016). [5] C. English et al., IEDM, Dec 2016. [6] I. Datye et al., Nano Lett. 20, 1461 (2020). [7] A. Khan et al, in prep. (2020). [8] M. Aly et al., Computer 48, 24 (2015). [9] S. Vaziri et al., Science Adv. 5, eaax1325 (2019). [10] A. Sood et al. Nature Comm. 9, 4510 (2018). 

  Bio

  Eric Pop is a Professor of Electrical Engineering (EE) and Materials Science & Engineering (by courtesy) at Stanford, where he leads the SystemX Heterogeneous Integration focus area. He was previously on the faculty of UIUC (2007-13) and worked at Intel (2005-07). His research interests are at the intersection of electronics, nanomaterials, and energy. He received his Ph.D. in EE from Stanford (2005) and three degrees from MIT (MEng and BS in EE, BS in Physics). His honors include the Presidential Early Career Award (PECASE), Young Investigator Awards from the Navy, Air Force, NSF and DARPA, and several best paper and best poster awards with his students. He is an Editor of the journal 2D Materials, has served as General Chair of the Device Research Conference, and on program committees of IEDM, VLSI, APS, and MRS. In his spare time, he tries to avoid injuries while snowboarding and in a past life he was a DJ at KZSU 90.1 FM, from 2000-04. Additional information about the Pop Lab is available online at http://poplab.stanford.edu

   

  September 24, 2020

  Dr. Sarah Keller, University of Washington

  Gargantuan domains in living yeast vacuole membranes (and what could make them smaller)

  Abstract

  For decades, scientists have argued about the mechanisms of how living cell membranes acquire regions enriched in particular lipid and protein types. One highly contested theory has been that domains form via phase separation, as occurs in simple artificial membranes. This theory has been slow to gain acceptance because it contradicts the widespread assumption that inhomogeneities in living cell membranes are limited to sub-micron sizes (whereas phase separation results in much larger domains). Since the 1960s, researchers have reported tantalizing hints that membranes in yeast do indeed phase separate. However, proof of phase separation hinges on the observation of a reversible phase transition. Here, we provide that direct evidence for vacuole membranes of living yeast cells. Inversely, when might unusually small domains appear in artificial membranes? Current theories of membrane microemulsions and modulated phases present several firm hypotheses, which we test in simple vesicle systems. In our system, small, stable domains are only observed in membranes with the excess area. 

• Winter 2020

  January 9, 2020

  Andreas Kronfeld, Fermilab

  QCD is Everywhere

  Abstract

  Quantum chromodynamics (QCD) is the modern theory of the strong nuclear force and part of the Standard Model of elementary particles.  QCD is a beautiful theoretical construct that has required considerable human ingenuity to understand in detail.  The beauty, ingenuity, and peculiarities can be understood via examples from particle physics and nuclear physics, of course, but also from everyday life.

   

  January 23, 2020

  David Pine, New York University

  In pursuit of colloidal diamond

  Abstract

  While suspensions of colloidal particles self-assemble into a wide variety of crystalline lattices, making them assemble into the diamond lattice has proven elusive.  The desire to do so has been driven by the fact that the a dielectric diamond lattice exhibits the widest photonic band gap of any known crystalline structure.  Here we report on the progress of strategies to realize a colloidal diamond lattice using DNA-coated colloids in various guises: patchy particles, particle clusters, and superlattices.

   

  February 6, 2020

  Jordan Horowitz, University of Michigan

  Nonequilibrium thermodynamic limits to fluctuations and response

  Abstract

  Thermodynamics is a remarkably successful theoretical framework, with wide ranging applications across the natural sciences. Unfortunately, thermodynamics is limited to equilibrium or near-equilibrium situations, whereas most of the natural world, especially life, operates very far from thermodynamic equilibrium. Research in nonequilibrium statistical thermodynamics is beginning to shed light on this domain. In this talk, I will present two such recent predictions. The first is a bound that quantifies how dissipation shapes fluctuations far from equilibrium. Besides its intrinsic allure as a universal relation, I will discuss how it can be used to offer energetic constraints on chemical clocks, and bound the dissipation in complex materials.  The second is a collection of equalities and inequalities---akin to the Fluctuation-Dissipation theorem but valid arbitrarily far from equilibrium---that link a system’s response to the strength of nonequilibrium driving.  These results open new avenues for experimentally characterizing nonequilibrium response and suggest design-principles for high-sensitivity, low-noise devices.  I will also discuss how they rationalize the energetic requirements of some common biochemical motifs.

   

  February 27, 2020

  Douglas M. Hudgins, NASA

  An Introduction to NASA’s Astrophysics Division and the Exoplanet Exploration Program

  Abstract

  To many in the scientific community, NASA appears to be a “black box” containing a bewildering array of field centers, missions, projects, research programs, and who knows what else. In fact, there *is* some method to the madness, and I hope to convince you of that fact. In this talk I will provide an introduction to NASA’s Astrophysics Division—who we are, how the division is structured, the avenues by which we support the community through our missions and research programs, and the ways that we engage the scientific community. From there, I will go on to focus on the Exoplanet Exploration Program (ExEP)—the program responsible for implementing NASA's plans for discovering and characterizing exoplanets, and identifying candidates that could harbor life. We will see that the Program encompasses a wide range of projects and activities from future mission concept studies, and technology development programs to enable those missions, to precursor and follow-up ground-based science programs that enhance the science return of current NASA missions and enable the design of next generation exoplanet missions. I will feature some recent highlights from the Program’s activities and describe the ways that the Program interfaces and supports the scientific community, and is paving the way to the future.

   

  March 5, 2020

  Spencer Klein, Lawrence Berkley National Laboratory

  The highest energy photons: using ultra-peripheral collisions at the LHC
  and RHIC to probe nuclear structure and test the standard model

  Abstract  

  High-energy photons are a simple tool with many uses.  The most energetic photons today are those that are produced in ultra-peripheral collisions (UPCs) involving protons or heavier ions.   The relativistically boosted electromagnetic fields of these ions act like a flux of nearly-real photons.  To the target (other) nucleus, the energies reach the PeV (10^15 eV) range.  I will discuss a number of physics topics that are being studied using these photons, including photon-photon scattering, production of antihydrogen atoms, and using these photons to probe nuclear structure, particularly via vector meson photoproduction.   Photoproduction is sensitive to the density and spatial distribution of gluons with very low momentum (Bjorken-x).  Finally, I will conclude with a brief look forward to the recently approved ("CD-0" in Dept. of Energy parlance) electron-ion collider..

   

  March 19, 2020

  Annika Peter, Ohio State University

  Testing the nature of dark matter with galaxies

  Abstract 

  The nature of dark matter is unknown.  The leading paradigm for dark matter is that it consists of at least one species of non-relativistic ("cold"), weakly interacting particles, the cold dark matter (CDM) paradigm.  One of the strongest predictions of CDM is the hierarchy of structure down to Earth-mass scales.  However, individual self-bound clumps of dark matter--"halos"--are difficult to detect directly.  Instead, we use galaxies, which grow at the centers of halos, as lampposts for these halos.  By counting galaxies, we can measure the underlying population of dark matter halos, and test the nature of dark matter.  In this talk, I describe two results that seem completely at odds with each other in measuring the population of small halos.  I argue that the resolution to the problem is a better mapping between galaxies and halos.  I will show what my group is doing so far to address the problem, and what opportunities lie ahead in the wide-field surveys of the 2020's.

   

  March 26, 2020

  David Wineland, University of Oregon

  Vaden Miles Lecture, "Quantum Computers and Raising Schrödinger's Cat"

  Abstract  

  Quantum systems such as atoms can be used to store information. For example, we can store a binary bit of information in two energy levels of an atom, labeling the state with lower energy a “0" and the state with higher energy a “1.” However, quantum systems can also exist in superposition states, thereby storing both states of the bit simultaneously, a situation that makes no sense in our ordinary-day experience. This property of quantum bits or “qubits” potentially leads to an exponential increase in memory and processing capacity. It would enable a quantum computer to efficiently solve certain problems such as factorizing large numbers, a capability that could compromise the security of current encryption systems. It could also be used to simulate the action of other important quantum systems in cases where such a simulation would be intractable on a conventional computer. A quantum computer could also realize an analog of "Schrödinger's Cat," a bizarre situation where a cat could be simultaneously dead and alive. Experiments whose goal is to realize a quantum computer based on laser manipulations of atomic ions will be described but this is just one platform that many groups around the world are investigating.

   

  April 2, 2020

  Xiaoming Mao, University of Michigan

   

   

  April 9, 2020

  Wei Zhang, Oakland University

  From Hybrid Quantum Magnonics to Terahertz Spintronics

  Abstract 

  Hybrid magnonic systems are great candidates for making interconnects between different quantum platforms, due to their coherent and strong coupling with other quantum excitations. The ability for sensitively and reliably probing the magnon dynamics in various novel spintronic and magnonic contexts are thus crucial, for example, involving state-of-the-art approaches using spin-torques, acoustic phonons, and microwave photons. I will discuss our recent results on the detection of phase-resolved magnetization dynamics using a cw-modulated laser technique, which allows a modulation at the GHz frequencies with both amplitude- and phase-control and also phase-locking to a microwave source. We show ferromagnetic resonance measurement of both metals and insulators, as well as the quantification of spin-orbit torques in ferromagnet/heavy-metal bilayers [1]. We also demonstrated the facile optical detection of magnon-magnon coupling in Permalloy/Y3Fe5O12 bilayers using this technique via a combination of magneto-optical Kerr and Faraday effects [2,3]. In particular, these measurements provide direct information on how the excitation of magnons in permalloy modes may suppress the excitation of magnons in YIG analogous to previously observed magnetically-induced-transparency effects in magnon-photon hybrid systems. Finally, I will make connections to a new spintronic material system for achieving strong and controllable ultrafast dynamics beyond GHz and up to THz frequency range.

  References:

  [1] Yi Li et al, “Simultaneous Optical and Electrical Spin-Torque Magnetometry with Phase-Sensitive Detection of Spin Precession”, Phys. Rev. Applied 11, 034047 (2019).

  [2] Yuzan Xiong et al, “Probing the Magnon-Magnon Coupling using Combinatorial Magneto-Optical Kerr and Faraday Effects”, ArXiv: 1912.13407.

  [3] Yi Li et al, “Coherent spin pumping in a strongly coupled magnon-magnon hybrid system”, Phys. Rev. Lett. in press (2020).

   

   

• Fall 2019

  September 19, 2019

  James Wells, University of Michigan

  Seeking clues on why matter won over antimatter

  Abstract

  One of the most intriguing mysteries of nature is why there is more matter in the universe than anti-matter given that the basic laws of particle physics do not appear to allow for it. One promising direction of explanation attacks the conservation of baryon number, which I will argue is one of the most vulnerable principles in fundamental physics. Forthcoming proton decay and neutron oscillations experiments may reveal much about just how the universe managed to make us and not anti-us.

   

  September 26, 2019

  Aurelia Honerkamp-Smith, Lehigh University 

  Membrane protein transport: Balancing advection and diffusion

  Abstract

  The fluidity of lipid membranes is essential to their biological function: cell membranes are required to be flexible, self-healing, and deformable. An additional consequence of membrane fluidity is that both lipids and proteins are highly mobile, which makes it possible for lipid-anchored proteins to travel long distances across the surface of cells. The significance of this lateral mobility for flow mechanosensing has not yet been determined. We study the mechanics of lateral membrane protein transport by flow in an in vitro model of the cell plasma membrane, lipid bilayers supported on glass. We prepare supported bilayers formed from individual GUVs inside microfluidic channels in order to study transport of membrane-anchored proteins. We observe and fit dynamic protein concentration gradients, which allow us to define protein mobility relative to a stationary lipid membrane.

   

  October 3, 2019

  Dean Lee, Michigan State University

  Lattice Simulations of Nuclear Structure and Thermodynamics

  Abstract

  In this talk I give an introduction to the method of lattice effective field theory, which is the combination of effective field theory and numerical lattice techniques.  I then discuss several recent results from the Nuclear Lattice Effective Field Theory Collaboration.  The first is the connection between microscopic nuclear forces and nuclear structure.  This centers on a basic question of what are the truly essential features of the nuclear force needed to produce the observed properties of atomic nuclei.  The second is the development of first principles simulations of the thermodynamics of nuclei and nuclear matter.

   

  October 17, 2019

  William Llope, Wayne State University

  Correlations in relativistic heavy-ion collisions

  Abstract

  In modern collider experiments, scientists collide atomic nuclei going at the speed of light in order to create large systems of deconfined quarks and gluons called the quark-gluon plasma (QGP). The scientists try to measure every particle produced in the collision in order to try to completely reconstruct the physics of the QGP, the state of our universe a few microseconds after the Big Bang. By measuring as many particles as possible per collision in a wide acceptance, scientists can explore multi-particle correlations, which indicate both prosaic reaction mechanisms (like momentum conservation) and potentially more exotic (and as yet undiscovered) mechanisms such as a critical opalescence - a beam-energy localized growth of long-range correlations signalling the existence of a critical point in the nuclear matter phase diagram. My two research groups work in two different but related directions. One group explores these correlations, and their integrals called the "fluctuations," by analyzing the experimental data collected by the STAR experiment at RHIC. My other group has been building new large-scale detector upgrades to improve the data coming from these modern experiments. The status and outlook of these efforts will be presented.

   

  October 24, 2019

  Indara Suarez, Boston University

  Desperately Seeking SUSY

  Abstract 

  Questions surrounding the measured value of the Higgs mass as well as astrophysical evidence for Dark Matter suggest that new particles and/or interactions are awaiting discovery. With the significant increase in collision energy and the large datasets of the LHC Run-2, we have continued our hunt for physics beyond the Standard Model by developing new strategies and machine-learning tools.  I will discuss the ongoing searches for Supersymmetric partners of the top quark, called top squarks or "stops", and how their discovery could shed light onto the nature of the lightness of the Higgs mass and Dark Matter.  My talk will focus on the detector upgrades that laid the foundation for exploiting the Run-2 data, the most recent results, and possible future directions in our search for new physics.

   

  October 31, 2019

  Kate Scholberg, Duke University

  Detecting the Tiny Thump of the Neutrino

  Abstract

  Neutrinos interact only rarely with matter.   Coherent elastic neutrino-nucleus scattering (CEvNS) was first predicted in 1974; it’s a process in which a neutrino scatters off an entire nucleus.  By neutrino standards, CEvNS occurs frequently, but it is tremendously challenging to see. The only way to observe it is to detect the minuscule thump of the nuclear recoil. CEvNS was measured for the first time by the COHERENT collaboration using the unique, high-quality source of neutrinos from the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory.   This talk will describe COHERENT's recent measurement of CEvNS, the status and plans of COHERENT's suite of detectors at the SNS, and the physics we will learn from the measurements.

  November 7, 2019

  Elena Gallo, University of Michigan

  A census of the black hole population in nearby low mass galaxies

  Abstract

  It is commonly accepted that a supermassive black hole – as massive as several millions or even billions Suns – sits at the center of every galaxy that is as large as (or larger than) the Milky Way galaxy. Additionally, the black hole is thought to play a critical role in shaping the large-scale properties of the galaxy it lives in. It does so by blowing galaxy-scale outflows of energy and matter, which in turn affect the fate of its host galaxy gas reservoir, and, ultimately, its ability to form stars. Whether a similar feedback mechanism takes place is not obvious when it comes to dwarf galaxies, i.e. galaxies that are one tenth of a Milky Way, or smaller. Even though dwarfs make up the overwhelming majority of the galaxy population out there, it is not clear whether all dwarf galaxies host a massive black hole at their center, and, if they do, whether the properties of those black holes, and chiefly their masses, scale with the overall galaxies’ properties the same way they do in larger galaxies. Part of the uncertainty has to do with the fact that standard “dynamical techniques”, which use the motion of gas and stars around the black hole to infer its presence, rely on being able to spatially resolve the black hole's gravitational sphere of influence. Yet the fraction of dwarf galaxies that host a massive black hole is of great interest to astronomers. The reason goes beyond simple demographics; the “black hole occupation fraction” in today’s dwarf galaxies is expected to be sensitive to the very mechanism through which these giant black holes were born when the Universe was still in its infancy. Surprisingly, this remains an open question. During this talk, I will present recent results from my group addressing these questions, in an effort to build a complete census of the population of nearby, massive black holes.

   

  December 5, 2019

  Michael Strickland, Kent State University

  Bottomonium suppression in the quark-gluon plasma

  Abstract

  The suppression of bottomonia in ultrarelativistic heavy-ion collisions is a smoking gun for the production of a long-lived strongly interacting final state.  Moreover, the experimentally observed suppression is consistent with the production of a hot hydrodynamically expanding quark-gluon plasma (QGP) with initial temperatures on the order of 600-700 MeV at LHC collision energies. Theoretical models which incorporate plasma screening and in-medium bound-state breakup based on high-temperature quantum chromodynamics are in good agreement with the centrality, transverse-momentum, and rapidity dependence of the experimentally observed suppression.  Importantly, these models are self-consistently coupled to the soft dynamics of the QGP using 3+1d relativistic hydrodynamics which provides tight constraints on the evolution of the QGP temperature, etc. The resulting model comparisons with LHC experimental data indicate primordial suppression of all bottomonium states, with states having the lowest binding energies suffering the most suppression. I will review recent theoretical and experimental advances in the study of in-medium heavy quarkonia suppression and discuss these advances in the larger context of the hunt for the QGP.

• Winter 2019

  April 11, 2019

  Prof. Alexey A Petrov, Wayne State University

  Charming asymmetry between matter and antimatter

  Abstract

  One of the conditions for creating a matter-dominated Universe is presence of interactions that differentiate between matter and anti-matter. Properties of such interactions can be probed at particle accelerators by studying decay patters of produced particles. On March 21, one of the CERN's experiments, the LHCb, announced observation of CP-violation in the decays of particles containing charm quark. I discuss theoretical implications of this important discovery, and why it took experimentalists such a long time to make this observation. I will also discuss why it would take even longer for theorists to discern it.

• Fall 2018

  September 13, 2018

  Lu Li, University of Michigan

  Quantum Oscillations of Electrical Resistivity in an Insulator

  Abstract

  In metals, orbital motions of conduction electrons are quantized in magnetic fields, which is manifested by quantum oscillations in electrical resistivity. This Landau quantization is generally absent in insulators, in which all the electrons are localized. Here we report a notable exception in an insulator — ytterbium dodecaboride (YbB12). The resistivity of YbB12, despite much larger than that of usual metals, exhibits profound quantum oscillations under intense magnetic fields.

  This unconventional oscillation is shown to arise from the insulating bulk, instead of conducting surface states. The large effective masses indicate strong correlation effects between electrons. Our result is the first discovery of quantum oscillations in the electrical resistivity of a strongly correlated insulator and will bring crucial insight to the understanding of the ground state in gapped Kondo systems.

   

  September 20, 2018

  Prashant Padmanabhan, Los Alamos National Lab

  From plasmons to skyrmions: The ultrafast dynamics and control of novel excitations and materials

  Abstract

  Over the last several decades, advances in ultrafast spectroscopy have enabled us to investigate fundamental phenomena associated with the electronic, lattice, and spin degrees of freedom in condensed matter systems at their intrinsic time-scales. Moreover, intense femtosecond pulses allow us to drive materials far from equilibrium. This provides us with access to states that are often difficult, or even impossible, to probe under normal thermodynamic conditions.

  As such, we can now examine the subtleties of exotic excitations, elucidate the microscopic coupling mechanisms between competing subsystems, and transiently manipulate the fundamental properties of novel materials. This talk will focus on such efforts in systems spanning prototypical semiconductors to quantum materials. Specific topics include massless collective excitations of multi-component plasmas, hole scattering dynamics in incipient ferroelectrics, and the optical control of low energy excitations in topologically protected spin textures.

   

  September 27, 2018

  Nagesh Kulkarni, Quarkonics Inc.

  From Ph.D. to CEO: An Entrepreneurial Journey

  Abstract

  A Physics education provides general skills in problem-solving, teamwork, and knowledge in cutting--edge technologies. Add some business skills and a physicist can become an entrepreneur. I will talk about my entrepreneurial journey and share my experiences and thoughts on how scientists can play a significant role in shaping the global economy, change the game, and create tremendous value for society by leveraging their unique analytical thinking and problem-solving skills, networking, and specialized knowledge.

   

  October 4, 2018

  Yaqiong Xu, Vanderbilt University

  Carbon-Based Nanomaterials for Biosensing

  Abstract

  Carbon-based nanomaterials, such as carbon nanotubes (CNTs) and graphene, have gained significant interest as one of the most promising materials in biological applications due to their unique physical and chemical properties. Recently we have developed an optoelectronic probing system, combining CNT/graphene transistors with scanning photocurrent measurements, fluorescence microscopy, and optical trapping techniques to investigate the molecular interface between CNTs/graphene and biological systems. We have directly measured the binding force between a single DNA molecule and a CNT in the near-equilibrium regime, where two aromatic rings spontaneously attract to each other due to the noncovalent forces between them. We have also integrated graphene-based scanning photocurrent microscopy with microfluidic platforms to investigate the electrical activities of individual synapses of primary hippocampal neurons. I will conclude by summarizing the remaining research challenges that must be surmounted in order to bring carbon-based nanomaterials into future biological applications.

   

  October 11, 2018

  Sergio E. Ulloa, Ohio University

  Putting Things on Top of Other Things (Proximity effects in 2D materials)

  Abstract

  Proximity effects such as those produced when depositing graphene on a transition metal dichalcogenide substrate are expected to change the dynamics of the electronic states in graphene, inducing spin-orbit coupling and staggered potential effects. Putting things on top of other things is promising and going strong in 2D materials!
  In this talk, I will describe some of the expectations of combining different layered materials. In particular, I will show how an effective Hamiltonian that describes different symmetry breaking terms in graphene, while preserving time reversal invariance, shows that a new topological insulator may be created by stacking "trivial" materials and applying strong electric fields. These new systems may exhibit quantum spin Hall and valley Hall effects in different conditions [1].

   [1] A.M. Alsharari, M.M. Asmar and S.E. Ulloa, Phys. Rev. B 94, 241106(R) (2016); and Phys. Rev. B 97, 241104(R) (2018).

   

  October 18, 2018

  Igor Žutić, University at Buffalo

  Proximity Effects in van der Waals Materials

  Abstract

  Advances in heterostructures and atomically thin van der Waals materials, such as graphene, suggest a novel approach to systematically design materials. A given material can be transformed through proximity effects whereby it acquires properties of its neighbors, for example, becoming superconducting, magnetic, topologically nontrivial, or with an enhanced spin-orbit coupling [1]. Such proximity effects not only complement the conventional methods of designing materials by doping or functionalization but also can overcome their various limitations. In proximitized materials, it is possible to realize properties that are not present in any constituent region of the considered heterostructure. While the focus is on magnetic proximity effects with their applications in spintronics [2-4], the outlined principles also provide a broader framework for employing other proximity effects to tailor materials and realize unexplored phenomena.

  1. I. Žutić et al., Mater. Today, (2018), arxiv:1805.07942, https://doi.org/10.1016/j.mattod.2018.05.003
  2. P. Lazić et al., Phys. Rev. B 93, 241401(R) (2016)
  3. B. Scharf et al., Phys. Rev. Lett. 119, 127403 (2017)
  4. J. Xu et al., Nat. Commun. 9, 2869 (2018)

   

  November 1, 2018

  Weihong Qiu, Oregon State University

  Kinesin-14s: Moving into a New Paradigm

  Abstract

  Kinesin-14s are microtubule-based motor proteins that play important roles in cell division. They were originally thought to be minus-end-directed nonprocessive motors that exhibit directional preference toward the microtubule minus ends in multi-motor ensembles but are unable to generate processive (continuous) motility on single microtubules as individual motors. During the past five years, we and others have discovered several "unconventional" kinesin-14 motors that all contain the ability to generate processive motility as individual motors on single microtubules. In this talk, I will present a series of unexpected yet exciting findings from my lab that have markedly expanded current view of the design and operation principles of kinesin-14 motors.

   

  November 27, 2018

  Ron Soltz, Lawrence Livermore National Lab

  Evaluating the Iran Nuclear Deal

  Abstract

  The Iran Nuclear Deal evokes strong reactions. It has been called "The Worst Deal Ever" as well as "The best option for preventing Iran from obtaining a nuclear weapon. Otherwise known as the "Joint Comprehensive Plan of Action", the JCPOA has led to much debate, even if little of it has been substantive. Put into effect in 2015, the JCPOA continues to influence the behavior of six of the seven signatories, the seventh having formally withdrawn 2018, reimposing sanctions in May and November. In the history of international agreements, it is truly unique, but as it stands at the intersection of science and policy, it is also a valuable teaching tool for the role that science can play in formulating good policy, while also providing an opportunity to review a few basic concepts in nuclear physics.

   

  November 29, 2018

  Gerald Gabrielese, Northwestern University

  Stringent Tabletop Tests of the Standard Model:  A Tale of the Electron's Electric and Magnetic Dipole Moments

  Abstract

  The standard model's most precise prediction -- of the size of the electron magnetic moment -- is tested using a single electron suspended by itself for months at a time in a tabletop-sized measurement.  Also, a new measurement of the electrons' other moment -- its electric dipole moment - was just completed in a very different tabletop measurement. The standard model and proposed alternatives/additions differ sharply in their predictions of the size of this moment.

   

  December 6, 2018

  Francis Halzen, Wisconsin IceCube Particle Astrophysics Center and Department of Physics, University of Wisconsin–Madison

  IceCube: Opening a New Window on the Universe from the South Pole.

  Abstract

  The IceCube project has transformed a cubic kilometer of natural Antarctic ice into a neutrino detector. The instrument detects more than 100,000 neutrinos per year in the GeV to PeV energy range. Among those, we have isolated a flux of high-energy neutrinos of cosmic origin. We will explore the IceCube telescope and the significance of the discovery of cosmic neutrinos. We recently identified their first source: alerted by IceCube on September 22, 2017, several astronomical telescopes pinpointed a flaring galaxy powered by an active supermassive black hole, as the source of a cosmic neutrino with an energy of 290 TeV. Most importantly, the large cosmic neutrino flux observed implies that the Universe's energy density in high-energy neutrinos is close to that in gamma rays, suggesting that the sources are connected and that a multitude of astronomical objects await discovery.

• Winter 2018

  January 18, 2018

  Shanshan Cao, Wayne State University

  Probing the Quantum Chromodynamic fluid with relativistic nuclear collisions

  Abstract

  Nuclear matter is heated beyond two trillion degrees in relativistic heavy-ion collisions and becomes a strongly coupled plasma of quarks and gluons. This highly excited quark-gluon plasma (QGP) matter displays properties of the perfect fluid and is believed similar to the state of the early universe microseconds after the big bang. In this talk, high-energy particles and jets are utilized to probe the QGP properties. A linear Boltzmann transport coupled to hydrodynamic model is established to describe the strong interaction between energetic partons and the QGP. This includes diverse microscopic processes for both massless and massive parton scatterings, and provides a simultaneous description of the nuclear modification of heavy and light flavor hadrons observed at the RHIC and LHC experiments. To precisely extract transport coefficients of the QGP, a statistical analysis framework that includes machine learning and Bayesian methods is developed, which brings a paradigm shift in statistical comparisons between theory and experiment.

   

  January 25, 2018

  ChunNing (Jeanie) Lau, Ohio State University

  Spin, Charge and Heat Transport in Low-Dimensional Materials

  Abstract

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

  Bio

  Dr. Chun Ning (Jeanie) Lau is a Professor in the Department of Physics at The Ohio State University. She received her BA in physics from the University of Chicago in 1994, and Ph.D. in physics from Harvard in 2001. She was a research associate at Hewlett Packard Labs in Palo Alto from 2002 to 2004, before joining the University of California, Riverside in 2004 as an assistant professor. She was promoted to associate professor in 2009 and full professor in 2012. Starting January 2017 she moved to The Ohio State University. Her research focuses on electronic, thermal and mechanical properties of nanoscale systems, in particular, graphene and other two-dimensional systems.

   

  January 30, 2018

  Vladimir Skokov, Brookhaven National Lab

  Quantum ChromoDynamics in extreme conditions

  Abstract

  In my talk, I discuss two landscapes of Quantum ChromoDynamics (QCD), the theory of strong interactions, in extreme conditions. I start with hot and dense QCD, which can be probed in the collisions of heavy-ions at high energy. The goal of the heavy-ion program is to map and study the QCD phase diagram and establish the existence of a conjectured critical point in QCD. The identification of this prominent landmark in the phase diagram is possible owing to its unique signature. I argue that recent experimental measurements agree with the theoretical expectations and, if confirmed, may lead to the discovery of a QCD critical point. I then turn to the landscape of cold QCD to be probed at a future Electron-Ion Collider. I discuss one of the exciting features which is the linear polarization of strong quasi-classical gluon fields in an unpolarized nucleus.

   

  February 1, 2018

  Li Yan, McGill University

  A droplet of QGP in the little bang

  Abstract

  One of the fundamental questions in high energy nuclear physics is how to understand the dynamics of matter systems dominated by strong interactions. Especially, in systems where temperatures are comparable to the QCD energy scale (~10¹² K), such as the universe in the first microseconds after Big Bang, or in high energy heavy-ion collisions carried out at RHIC and the LHC (the Little Bang), our interest is in a novel state of matter – quark-gluon plasma (QGP). One of the significant properties of QGP is its perfect fluidity. Actually, the value of shear viscosity over entropy density ratio of QGP has been found to be very close to a theoretical lower bound. The fluidity the QGP plays an essential role in the present studies of heavy-ion experiments. QGP evolution dominates the observed correlation behaviors of the produced particles in nucleus-nucleus collisions (large colliding systems), proton-lead and even proton-proton collisions (small colliding systems). In this talk, I will demonstrate how the idea of QGP fluidity emerges from the observed phenomena in experiments. I will also explain how a "standard model" of heavy-ion collisions based on relativistic hydrodynamics is challenged by the fluid behavior in recent small colliding systems.

   

  February 8, 2018

  Chun Shen, Brookhaven National Lab

  Going with the flow — the nuclear phase diagram at the highest temperatures and densities

  Abstract

  The nuclear matter has a complex phase structure, with a deconfined Quark-Gluon Plasma (QGP) expected to be present under conditions of extreme pressure and temperature. The hot QGP filled the universe about few microseconds after the Big Bang. This hot nuclear matter can be generated in the laboratory via the collision of heavy atomic nuclei at high energy. I will review recent theoretical progress in studying the transport properties the QGP. Recently, the Relativistic Heavy-Ion Collider (RHIC) conducted the beam energy scan experiments. It offered a unique opportunity to study the nuclear phase diagram in a hot and baryon-rich environment. I will focus on the development of a comprehensive framework that is able to connect the fundamental theory of strong interactions with the RHIC experimental observables. This dynamical framework paves the way for quantitative characterization of the QGP and for locating the critical point in the nuclear phase diagram. These studies will advance our understanding of strongly interacting many-body systems and build interconnections with other areas of physics, including string theory, cosmology, and cold atomic gases.

   

  February 15, 2018

  Mauricio Guerrero, North Carolina State University

  Out of equilibrium dynamics: Lessons from Nuclear Collisions

  Abstract

  The current knowledge of the universe is highly constrained without understanding the formation of baryonic matter widely observed today. It is then required to know the precise details of the transition where a highly dense plasma composed by quarks, antiquarks, and gluons combine to form hadrons. Ultrarelativistic heavy ion experiments can recreate non-equilibrium extreme conditions of the early universe by colliding heavy nuclei moving nearly at the speed of light. One of the major scientific discoveries of this century is the observation of a tiny, short-lived quark-gluon plasma (QGP). This extreme state of matter behaves like a liquid with a very small viscosity. Recently,  we have learned that the perfect fluidity property, observed first in nucleus-nucleus collisions, also extends to proton-nucleus and proton-proton collisions. The  "nearly perfect liquid" behavior of the QGP has opened up a new avenue for studying transport properties of strongly interacting systems. Nonetheless, these experimental findings challenge the theorists to develop better models which include the non-equilibrium evolution of the expanding nuclear matter created in those collisions. In this talk, I will review the 'standard model picture' of heavy ion collisions and present some recent theoretical studies which attempt to explain the unreasonable phenomenological success of fluid dynamical models in far from local equilibrium situations. I shall pose several unanswered questions about the QGP which emerge from these new theoretical developments and discuss how in the next few years, future experimental programs at large baryon densities and energy regimes will herald a new era of discovery and unraveling of the secrets of QGP.

   

  February 22, 2018

  Hong Guo, McGill University

  Electronic States of the Moiré superlattice

  Abstract

  Two-dimensional (2D) van der Waals (vdW) heterostructures have attracted great attention in the past five years. By stacking different 2D materials to bond via the vdW force, these artificial heterostructures provide interesting and new material phase space for exploration. In this talk, I shall focus on one aspect of the 2D vdW materials: the Moiré pattern. In visual arts, Moiré pattern is an optical perception of a new pattern formed on top of two similar stacking patterns. In 2D vdW heterostructures, the Moiré pattern is a physical superlattice which brings about novel electronic properties. To theoretically predict the physical properties of the Moiré superlattice, systems containing more than ten thousand atoms often need to be analyzed by first principles. In this talk, I shall begin by briefly discussing how one may break the "size limit" so that very large first principles simulations within the density functional theory can be carried out. Afterward, I shall present and discuss some of the calculated novel properties of the Moiré superlattice: the emergence of a secondary Dirac cone, the suppression of the carrier mobility, and the formation of multiple helical valley currents, on various 2D vdW heterostructure materials. Some of these properties can well be the basis of potential applications.

  Bio

  Dr. Hong Guo obtained B.Sc. in Physics at the Sichuan Normal University in China and Ph.D. in theoretical condensed matter physics at the University of Pittsburgh. In 1989, he joined the faculty of the Physics Department, McGill University in Montreal Canada. He is currently a James McGill Professor of Physics. His research includes quantum transport theory, nanoelectronic device physics, nonequilibrium phenomena, materials physics, density functional theory, mathematical and computational physics. He was elected to Fellow of the American Physical Society in 2004, and Fellow of the Royal Society of Canada (Academy of Sciences) in 2007. He received the Killam Research Fellowship Award from the Canadian Council for the Arts in 2004; the Brockhouse Medal for Excellence in Experimental or Theoretical Condensed Matter Physics of the Canadian Association of Physicists in 2006; and the CAP-CRM Prize in Theoretical and Mathematical Physics from Canadian Association of Physicists in 2009.

   

  March 2, 2018

  David Ceperley, University of Illinois at Urbana-Champaign, and member of the National Academy of Sciences

  How can we model the hydrogen inside Jupiter and Saturn?

  Abstract

  Jupiter, Saturn and a host of newly discovered exoplanets are thought to be composed largely of hydrogen and helium. To understand the planets, we need properties of hydrogen and helium under the extreme conditions of temperature and pressure inside those planets, conditions hardly accessible to laboratory measurements. I will describe how we use high-performance computers to calculate those properties and thus help understand some of the most important objects in the Universe.

  Bio

  Dr. David Ceperley is the Founder and Blue Waters Professor of Physics at the University of Illinois Urbana-Champaign, and a member of the National Academy of Sciences. He received his BS in physics from the University of Michigan in 1971 and his Ph.D. in physics from Cornell University in 1976. After one year at the University of Paris and a second postdoc at Rutgers University, he worked as a staff scientist at both Lawrence Berkeley and Lawrence Livermore National Laboratories. In 1987, he joined the Department of Physics at Illinois. He was a staff scientist at the National Center for Supercomputing Applications from 1987 until 2012. Professor Ceperley is a Fellow of the American Physical Society and a member of the American Academy of Arts and Sciences and was elected to the National Academy of Sciences in 2006. He has received many honors and awards.

   

  March 6, 2018

  LongGang Pang, Lawrence Berkeley National Laboratory

  Exploring the quantum chromodynamics phase transition with deep learning 

  Abstract

  The state-of-the-art pattern recognition method in machine learning (deep convolution neural network) has been used to classify two different phase transitions between normal nuclear matter and hot-dense quark-gluon plasma. Big amount of training data is prepared by simulating heavy ion collisions with the most efficient relativistic hydrodynamic program CLVisc. High-level correlations of particle spectra in transverse momentum and azimuthal angle learned by the neural network are quite robust in deciphering the transition type in the quantum chromodynamics phase diagram. Through this study, we demonstrated that there is a traceable encoder of the phase structure that survives the dynamical evolution and exists in the final snapshot of heavy ion collisions and one can exclusively and effectively decode this information from the highly complex output using machine learning.

   

  March 8, 2018

  Christoph Naumann, Indiana University - Purdue University Indianapolis

  Probing membrane protein organization and dynamics in planar model membranes using single molecule-sensitive confocal detection techniques 

  Abstract

  The organization and distribution of proteins in the plasma membrane is widely known to influence membrane protein functionality. However, it remains challenging to decipher the underlying mechanisms that regulate membrane protein properties in the complex environment of cellular membranes. To overcome these challenges, an experimental strategy is discussed, in which the distribution, oligomerization state, and mobility of membrane proteins can be explored in a planar polymer-tethered lipid bilayer of well-defined lipid compositions using single molecule-sensitive confocal detection strategies. Results from such model membrane experiments are presented, which explore the influence of native ligands, bilayer asymmetry, and cholesterol content on the sequestration/oligomerization of urokinase plasminogen activator receptors (uPAR) and integrins [1-4]. Moreover, dual-color confocal experiments are described, which provide information about the formation and composition of uPAR-integrin complexes and the role of membrane cholesterol therein. Polymer-tethered lipid bilayer systems, comprised of phospholipids and lipopolymers, are also characterized by remarkable materials properties, which make them suitable as cell surface-mimicking substrates for the analysis of adhesion and spreading of plated cells. To illustrate the feasibility of such an application, we discuss the assembly of cadherin chimera into clusters on the surface of a polymer-tethered lipid bilayer substrate to form stable cell-substrate cadherin linkages underneath migrating C2C12 myoblasts [5]. Cluster tracking experiments reveal the cytoskeleton-regulated long-range mobility of cell-substrate linkages, thereby displaying remarkable parallels to the dynamics of cadherin-based cell-cell junctions.

  [1] A. P. Siegel et al. (2011) Biophys. J. 101, 1642.
  [2] N. F. Hussain et al. (2013) Biophys. J. 104, 2212.
  [3] Y. Ge et al. (2014) Biophys. J. 107, 2101.
  [4] Y. Ge et al. (2018) Biophys. J. 114, 158.
  [5] Y. Ge et al. (2016) Soft Matter 12, 8259.

   

  March 22, 2018

  W.J. Llope, Wayne State University

  How to give a great talk – tips for success and traps to avoid

  Abstract

  Whether your future lies in academia or industry, you will have opportunities to present your recent work while standing in front of an audience of interested people. Giving a good talk is a very powerful advertisement of you and your efforts, and, if you can properly enthuse the audience during your talk, the subsequent discussions can be very helpful for your future work. Great talks come in many forms, but all share a few key positive aspects and all avoid some (unfortunately rather common) pitfalls. This colloquium will share some tips from what I've learned over the years while watching thousands of talks, and giving a few myself. This presentation is specifically aimed at our students and postdocs, although the faculty are of course welcome to share their insights as well. The atmosphere will be informal and an open discussion, especially with our younger colleagues, will be encouraged.

   

  March 29, 2018

  Vladimir Chernyak, Department of Chemistry, Wayne State University

  Integrability in Non-Equilibrium Quantum Dynamics

  Abstract

  Nonequilibrium quantum dynamics, i.e., quantum evolution with time-dependent Hamiltonians, iħ ∂Ψ(t)/∂t = Ĥ(t)Ψ(t), as of today draws considerable attention, both in experimental and theoretical research. The simplest model with Ĥ(t)=A+Bt, and A and B being 2×2 real hermitian matrices, known as the Landau-Zener (LZ) problem has an exact solution in special functions, with the scattering matrix S, expressed in term of Gaussians and Euler Gamma-function. In the general N-dimensional case, known as Multilevel LZ (MLZ) problem, exact solutions are not available. However, for a certain class of MLZ problems that satisfy certain phenomenologically determined "integrability" conditions, including, but not limited to Demkov-Osherov (DO), Generalized Bow-Tie (GBT), and Tavis-Cummings (TC), the scattering matrix can be represented in a factorized form, with the elementary scattering events being represented in terms of the standard LZ matrix, which is the first aspect of integrability; in other words the semiclassical expressions become exact.

  In this talk we reveal the reason that stands behind the aforementioned factorization: Each integrable MLZ problem can be embedded into a system of M linear first-order differential equations with respect to M-dimensional time, that satisfy the consistency conditions, the latter having a form of the zero-curvature conditions, which is the second and dynamical aspect of integrability.

  We further apply our approach to obtain an exact solution for the BCS model that does not belong to the MLZ class, but rather describes decay of the initial strongly correlated state of Ns quantum spins (in the thermodynamic Ns→∞ limit the model becomes a non-trivial field theory) into an uncorrelated counterpart when the spin-spin interaction is switched off, and generally in a non-adiabatic fashion. The obtained exact solution shows an amazing property: The ground state in the strongly correlated phase "dissociates" into a Gibbs distribution in a completely integrable way, without any chaos or bath involved. We demonstrate that the aforementioned result is a third aspect of integrability, which is the natural appearance of the structures, usually associated with quantum integrability in a form of algebraic Bethe Ansatz, including the Yang-Baxter-Zamolodchikov (YBZ) equation, Artin's Braid Group, and quantum group SUq(2).

  The presentation will be given in an intuitive fashion, all mathematical structures involved will be explained using the terms, which are common for a broad physics audience.

   

  April 5, 2018

  Prof. Aaron Pierce, Director of the Leinweber Center for Theoretical Physics at the University of Michigan

  Dark Matter: WIMPS and Beyond

  Abstract

  The identity of the Dark Matter that dominates the matter density of the universe remains a mystery.  Increasingly sophisticated experiments have begun to probe some of the best-motivated models of dark matter.  I will review the theoretical status of one such paradigm, so-called Weakly Interacting Massive Particle (WIMP) Dark Matter, with particular emphasis on the implications of direct detection experiments.  We will see that while the paradigm is alive and well, it is under non-trivial pressure, particularly in specific implementations, such as supersymmetry. This warrants searches for other types of Dark Matter.  I will very briefly discuss a few such searches, including a new possibility of using the LIGO gravitational wave detector as a dark matter detector.

   

  April 19, 2018: Vaden Miles Lecture

  J. Michael Kosterlitz, Brown University (2016 Nobel Prize in Physics)

  Topological Defects and Phase Transitions - A Random Walk to the Nobel Prize

  Abstract

  This talk is about my path to the Nobel Prize and reviews some of the applications of topology and topological defects in phase transitions in two-dimensional systems for which Kosterlitz and Thouless split half the 2016 Physics Nobel Prize. The theoretical predictions and experimental verification in two-dimensional superfluids, superconductors and crystals will be reviewed because they provide very convincing quantitative agreement with topological defect theories.

  Bio

  Dr. J. Michael Kosterlitz is a theoretical physicist recognized for his work with David J. Thouless on the application of topological ideas to the theory of phase transitions in two-dimensional systems with a continuous symmetry. The theory has been applied to thin films of superfluid 4He, superconductors and to melting of two-dimensional solids. This work was recognized by the Lars Onsager prize in 2000, membership in the AAAS 2007, and by the 2016 Nobel Prize in Physics. Dr. Kosterlitz graduated from Cambridge University earning a BSc in physics in 1965, an MA in 1966, and received a D. Phil. from Oxford in 1969. He was a postdoctoral fellow at Torino University, Italy, in 1970 and at Birmingham University, U.K., from 1970-73. There he met David Thouless and together they did their groundbreaking work on phase transitions mediated by topological defects in two dimensions. He was a postdoctoral fellow at Cornell in 1974, on the faculty at Birmingham 1974-81, Professor of Physics at Brown University 1982 – present, and elected to the National Academy of Sciences in 2017.

• Fall 2017 and prior

  View archive of fall 2017 colloquium and prior.