Physics Home


Spring 2021

The Colloquia are via Zoom on Thursdays at 4:05 PM

Contact: D. Tanner
Department of Physics Colloquium Committee:
Tanner (chair), Mitselmakher, Ramond, Wang, B. Xue, X.X. Zhang.

January 14


January 21

  Speaker John Klauder, University of Florida
  Title From Harmonic Oscillators to Quantum Gravity
  Abstract Canonical quantization (CQ) has been successful in solving many problems, and is a tool used for nearly all cases. But CQ has not worked well for some problems that have resisted any acceptable solution. Happily, the harmonic oscillator, with -∞ < p,q < ∞, is well solved. However, for the half-harmonic oscillator, where -∞ < p < ∞ while 0 < q < ∞ CQ fails significantly. Likewise, quantum gravity has failed with CQ as well. A new quantization process called affine quantization (AQ) will be introduced. AQ leads to acceptable solutions for the half-harmonic oscillator and shows considerable success for quantum gravity. This lecture will demonstrate the solution of the half-harmonic oscillator and leads to a meaningful Schrödinger equation for quantum gravity, which is in position to seek appropriate solutions from complex differential equations.
  Host Sergei Shabanov

January 28

  Speaker Pierre Sikivie, UF Physics
  Title Encounters with the Axion
  Abstract The notion of Peccei-Quinn symmetry with its concomitant axion has been astonishingly fertile, with surprising connections to most subfields of physics. A personal account is given of events, insights and experiments that contributed to its history so far.
  Host David Tanner

February 4 (jointly organized with MAE)

  Speaker David Wiese, NASA Jet Propulsion Laboratory, CIT
  Title Chasing Water: Tracking changes in Earth's water cycle from space
  Abstract The Gravity Recovery and Climate Experiment (GRACE), launched in 2002, provided pioneering observations of changes in surface mass on our planet by measuring variations in the gravitational potential of Earth. These observations quantified, for the first time, the mass balance of the ice sheets, the mass component of sea level change, glacier mass change worldwide, and identified regions of rapid groundwater depletion, raising concern for future regional water security. The GRACE mission was decommissioned in 2017 due to battery failure; however, GRACE Follow-On (GRACE-FO) launched in 2018 and is now successfully continuing observations of Earth system mass change. Further, the 2017 U.S. Earth Science and Applications from Space Decadal Survey listed Mass Change as a Designated Observable, paving the way for a future mission after GRACE-FO. In this talk, I will provide an overview of the measurement system characteristics and scientific highlights from the GRACE and GRACE-FO missions. I will also discuss current efforts underway both in the United States and Europe to develop observing systems that will continue the timeseries of surface mass change into the future beyond the lifetime of GRACE-FO, and have the potential to advance knowledge of surface mass change through improved spatio-temporal sampling characteristics and instrumentation.
  Host Pep Sanjuan (Physics), John Conklin (MAE)

February 11

  Speaker Julie Comerford, University of Colorado
  Title Cosmic Collisions: Galaxies, Black Holes, and Gravitational Waves
  Abstract Galaxy mergers play an important role in the evolution of the universe, since mergers trigger star formation, build up the mass of supermassive black holes, and drive supermassive black hole mergers that are strong sources of gravitational waves. However, accurate identification of galaxy mergers has been a persistent observational challenge that limits progress in these areas. Here, I will present new approaches to galaxy merger identification, including approaches that use stellar kinematics instead of imaging alone, and approaches that are trained on state-of-the-art cosmological simulations of galaxies. I will summarize the results of our study of galaxy mergers imaged by the Hubble Space Telescope, where we measure the impact of mergers on star formation and supermassive black hole growth. With our new measurements of the galaxy merger rate, we can predict the amplitude of the gravitational wave background produced by merging supermassive black holes. Pulsar timing arrays expect to make the exciting detection of this gravitational wave background within the coming few years.
  Host Laura Blecha

February 18

  Speaker Christopher Jarzynski (University of Maryland)
  Title Scaling down the laws of thermodynamics
  Abstract Thermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems also exhibit "thermodynamic-like" behavior - for instance, biomolecular motors convert chemical fuel into mechanical work, and single molecules exhibit hysteresis when manipulated using optical tweezers. To what extent can the laws of thermodynamics be scaled down to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will describe some of the challenges and recent progress - both theoretical and experimental – associated with addressing these questions. Along the way, my talk will touch on non-equilibrium fluctuations, "violations" of the second law, the thermodynamic arrow of time, nanoscale feedback control, strong system-environment coupling, and quantum thermodynamics.
  Host BingKan Xue

February 25

  Speaker Lisa Larrimore Ouellette, Stanford University
  Title Should Physicists Care About Patent Law?
  Abstract Academic science has become increasingly entwined with patent law in recent decades, with U.S. universities receiving over 5000 patents per year and bringing in billions of dollars in licensing income. But surprisingly little is known about how patents affect university research. Do scientists learn anything from the technical disclosures in patents? Could patents be improved by scientific peer review? How do the financial incentives from patents affect academic scientists? This lecture will describe my empirical research on these questions—drawn from my background as both a Ph.D. physicist and a lawyer—including survey results, a three-year randomized controlled field experiment on patent peer review, and a study of variation in patent royalty-sharing policies across universities.
  Host Kathryn McGill

March 4


March 11

  Speaker Eduardo Fradkin, University of Illinois
  Title Pair Density Waves and Intertwined Orders in High Tc Superconductors
  Abstract I will review the current status of our understanding of high temperature superconductors. I will argue that the complex set of orders seen in experiment naturally arise with the same strength and are better regarded as intertwined rather than competing. I illustrate this concept in the context of the orders that are present in the pair-density-wave state and the phase diagrams that result from this analysis.
  Host Yuxuan Wang

March 18

  Speaker Amandine Aftalion, CNRS senior scientist, Ecole des Hautes Etudes en sciences sociales, Paris, France
  Title Modelling of Racing
  Abstract In order to determine the optimal strategy to run a race according to the distance to run, we introduce a model based on a system of differential equations for the velocity, the propulsive force and the anaerobic energy. The system does not rely on statistics but couples mechanics, energetics (both aerobic and anaerobic), neural drive to an economic decision theory of cost and benefit. For a fixed distance to run (from 100m to 10 000m), we find how effort is minimized to produce the best running strategy. This takes into account the effect of the bend, of the lane and the psychological interaction with a neighbor on the next lane. We even suggest how present tracks could be modified to improve record times and decrease discrepancy between lanes.

March 22 Monday at 1 pm. NOTE Special day and time!

  Speaker Alice Pisani, Princeton University
  Title Unraveling the Universe with cosmic voids
  Abstract Modern surveys provide access to high-quality measurements on large areas of the sky, sampling the galaxy distribution in detail also in the emptiest regions, voids. Void cosmology is becoming an increasingly active sector of galaxy clustering analysis: by measuring void properties, such as density profiles or void number counts, it is possible to constrain cosmological parameters. Cosmic voids are particularly sensitive to the properties of dark energy and neutrinos, and are a powerful tool to test modifications of the laws of general relativity. Studying voids provides a novel perspective to unravel the unsolved mysteries of our Universe. In this talk I introduce cosmic voids as a tool for cosmology, I present recent results with a particular focus on the advantages of calibration-free approaches and I discuss future developments in the field.
  Host Guido Mueller

March 25

  Speaker Kirk Barrow
  Title Using High-Cadence Synthetic Observations to Unlock a New Era in Astrophysics
  Abstract As astronomers near the commissioning of the extremely large telescopes, the Rubin Observatory, as well as new space-based observatories like the Roman Space Telescope and JWST to peer more deeply into our Universe, our community is challenged to develop a theoretical and modeling framework to characterize and study what will be humanity's greatest astronomical discoveries. My research addresses this need by generating detailed, state-of-the-art synthetic observations from hydrodynamic cosmological simulations. By calculating all the processes that photons undergo as they travel across the Universe from the surface of a distant star to a telescope’s detector, my collaborators and I have been able to disentangle perplexing trends in observed galactic spectra as well as make predictions for what we might unveil in the near future. Topics we have investigated in prior work include massive black hole formation, the first stars and galaxies, and the intricate interplay between nebular emission lines and the escape fraction of ionizing radiation. Looking forward, I propose to create the largest and most detailed database of synthetic observational tools and predictions at a time that will come to define astronomy for generations.
  Host Guido Mueller

March 29 Monday at 1 pm. NOTE Special day and time!

  Speaker Richard Anantua, Center for Astrophysics, Harvard & Smithsonian
  Title A Glimpse into Horizon-Scale Physics by Observing Movies and Polarization Maps
  Abstract Recent observations of radio emission from inflowing and outflowing plasma in the vicinity of supermassive black holes are linked to simple phenomenological models via general relativistic magnetohydrodynamic simulations in a methodology called “Observing” Jet/Accretion flow/Black hole (JAB) Systems. For Sagittarius A* in our Galactic Center, intensity map movies simulating hourly timescales show that these models can be classified into at least four types: 1.) thin, asymmetric photon ring with best fit spectrum; 2.) coronal boundary layer with thin photon ring and steep spectrum; 3.) thick photon torus with flat spectrum; and 4.) extended outflow with flat spectrum. For M87, a HARM jet simulation is used to replicate the observed collimation and magnetic substructure, while serving as the basis for a self-similar, stationary, axisymmetric force-free outflow model used to generate polarization maps at Global mm-VLBI Array (86 GHz) and Event Horizon Telescope (230 GHz) scales. This model varies plasma content from ionic (e-p) to pair (e-e+). Emission at the observed frequency is assumed to be synchrotron radiation from electrons and positrons, whose pressure is set to relate to the local magnetic pressure through parametric prescriptions. Polarization maps and spectra are found to be observationally distinguishable through positron effects such as decreasing intrinsic circular polarization and increased Faraday conversion.
  Host Guido Mueller

March 30 Tuesday at 4:05 pm. NOTE Special day!

  Speaker Yuxuan Wang, UF Physics
  Title Symmetry-protected gates of Majorana qubits in a high-temperature superconductor platform
  Abstract I will first introduce the idea of using non-Abelian anyons for topological quantum computation and then propose a platform for braiding Majorana non-Abelian anyons based on a heterostructure between a high-temperature superconductor and a quantum spin-Hall insulator. We show that upon applying a magnetic field in the corner region, two Majorana modes can be manipulated for braiding processes by tuning the field. We show that such a setup can achieve full braiding, exchanging, and a long-sought-after Magic gate of the Majorana zero modes, all of which are robust and protected by symmetries. As many of the ingredients of our proposed platform have been realized in recent experiments, our results provides a new route toward topological quantum computation.

April 1

  Speaker Vanessa Boehm, UC Berkeley
  Title Machine Learning meets Astrophysics: A love marriage?
  Abstract The recent rise of artificial intelligence, fuelled by advances in parallel computing on Graphical Processing Units (GPUs), promises to revolutionize more than just automatic image classification. Astrophysicists have good reason to be excited: With datasets ever growing in size and complexity, machine learning promises to be a panacea for tackling the challenge of harvesting information from them. However, machine learning algorithms are often not designed with scientific applications in mind and can struggle with critical tasks such as uncertainty estimation. In my talk I will explore how we can make the most out of novel machine learning algorithms and related concepts, while meeting the needs of a rigorous scientific data analysis.
  Host Guido Mueller

April 5 Monday at 1 pm. NOTE Special day and time!

  Speaker Jeffrey Andrews
  Title It Takes Two to Tango: How Binary Stars Evolve into Gravitational Wave Sources
  Abstract With the discovery of dozens of merging black holes and neutron stars by gravitational wave observatories over the past five years, the study of the complexities of binary star evolution physics - including mass transfer, tides, and r-process nucleosynthesis - has taken on a new urgency. In this talk, I will describe the current status of binary evolution models as well as several critical shortcomings that I am working to systematically address. I will focus on both improvements to physical processes, such as the common envelope in which a neutron star or black hole becomes engulfed within a giant star’s envelope, as well as the introduction of modern statistical and machine learning methods using dedicated supercomputers.
  Host Guido Mueller

April 6 Tuesday at 4:05 pm. NOTE Special day!

  Speaker Paul Fulda, UF Physics
  Title Squeezing the best science out of laser interferometers: Gravitational wave detection from mHz to kHz
  Abstract Gravitational wave science has made the leap from the textbooks to the headlines over the last 5 years as LIGO and Virgo followed up the first detections with an avalanche of exciting discoveries. The future remains bright with a third generation of ground-based detectors like Einstein Telescope and Cosmic Explorer in the planning stages, and the space-based detector LISA marching towards a planned launch in 2034. I will summarize the current state-of-the-art of the ground-based observatories and the planned upgrades, and discuss progress towards LISA's mission goals. I'll then take a detour to discuss some of the more novel ways that gravitational wave detectors are adapted to reach their unprecedented sensitivities, including the use of squeezed vacuum fields to reduce the quantum measurement uncertainty. Finally, I'll give an overview of the ways in which my research group at UF is helping to push the boundaries of what can be achieved with laser interferometry.

April 8

  Speaker Jia Liu (UC Berkeley)
  Title Cosmology with Massive Neutrinos
  Abstract Ghostly neutrino particles continue to bring surprises to fundamental physics, from their existence to the phenomenon of neutrino oscillation, which implies their nonzero masses. Their exact masses, among the most curious unknowns beyond the Standard Model of particle physics, can soon be probed by the joint analysis of upcoming cosmological surveys including the Vera Rubin Observatory LSST, Simons Observatory, DESI, SPHEREx, Euclid, CMB-S4, and Roman Space Telescope. In this talk, I will first discuss ongoing works studying the effects of massive neutrinos. I will then turn the focus to my major efforts of modeling the challenging small-scale, nonlinear regime of cosmic structures where neutrino effects are expected to be strongest. Finally, I will draw a roadmap towards discovering the neutrino mass over the next decade.
  Host Laura Blecha/Guido Mueller

April 12 Monday at 10 am NOTE Special day and time!

  Speaker Daniel D'Orazio, Niels Bohr Institute, University of Copenhagen
  Title A Multi-messenger Exposé of the Biggest Black Hole Pairs in the Universe
  Abstract At the center of nearly every galaxy in the Universe resides a supermassive black hole. When galaxies collide, their supermassive black holes sink to the center of the newly forming galaxy. There in this nascent galactic nucleus a supermassive black hole binary is formed. Supermassive binaries are the subject of a long-standing mystery in astrophysics: will these monstrous black holes merge and what can that tell us about the extreme environments that shape them? Their mutual evolution with galaxies? And the low-frequency gravitational wave sky? To solve this problem, we need to advance binary population models that are currently limited by uncertainties in environment-assisted binary orbital evolution, and we importantly need to couple model predictions with observational constraints on the supermassive black hole binary population using both electromagnetic and gravitational tracers. I will discuss work on both of these fronts, and how in a few years a wealth of data from both gravitational wave (Pulsar Timing Arrays and in the next decade LISA) and time-domain electromagnetic observations (e.g., with the Vera C. Rubin Observatory) could usher in a golden era of discovery for supermassive black hole binaries and their astrophysical environments.

April 15


April 22

  Speaker Clifford Will, UF Physics
  Title Einstein Prize Talk: Is Einstein Still Right?
  Abstract In the spring of 1969, a naïve first-year graduate student from Canada was told by his Caltech advisor "Kip" to find out everything that was known at that time about the experimental tests of general relativity. Joseph Weber had just claimed the first detection of gravitational waves, contrary to all conventional wisdom, and Kip worried that general relativity might be wrong. At the time, the experimental evidence supporting the theory was thin, but change was in the air. Thus began a 50-year quest to answer the question: Was Einstein Right? That quest took the student from the Earth and the solar system to binary neutron stars; from the massive black hole in our own galaxy to merging black holes billions of light years away. We will give a broad overview of the themes and questions that drove this quest, drawing attention to some of the remarkable individuals encountered along the way.
  Host David Tanner - If you would like to hear the talk and do not get link and password via the Physics Department Seminar emails, then send an email to asking for the password.