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PHYSICS COLLOQUIUM SCHEDULE
Fall 2019
The Colloquia are in Room 1002 NPB on Thursday at 4:05 PM
Refreshments will be served starting at 3:15 PM in NPB 2205

Contact: A. Hebard afh@phys.ufl.edu)
Department of Physics Colloquium Committee:
Hebard (chair), Fulda, Matchev, Mitselmakher, Wang


August 22

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August 29
  Speaker Graduate Student Meeting with Dr. Xiaoguang Zhang 4:00pm in 1002 NPB
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September 5
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September 12
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September 19
  Speaker Kathryn McGill, UF Physics
  Title Physics Education Research (PER): A User’s Guide
  Abstract What is Physics Education Research (PER)? What does it say about physics education and the learning of physics? How long has this field existed, anyway? These are just a few of the questions I will answer in my talk. Additionally, I will present an overview of the implementation of PER-based methods in the UF Department of Physics, as well as introduce some PER studies being conducted by the UF physics lecturers.
Host Arthur Hebard

September 26
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October 3
  Speaker Kun Yang (Florida State University)
Title Condensed Matter Physics: What Happened Since Ashcroft/Mermin and Where Is It Going?
  Abstract The classic textbook by Ashcroft and Mermin, titled Solid State Physics, has dominated education of graduate students in the field of condensed matter physics since its publication in 1976. Tremendous progress has been made in this field over the past 40 years, and a modern textbook replacing this aging classic is in urgent need. In this talk I will report our attempt [1] to meet this need, and discuss the recent developments in condensed matter physics along the way, emphasizing its synergy with other fields. [1] Modern Condensed Matter Physics, Steven M. Girvin and Kun Yang
Host Dmitrii Maslov

October 10
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October 17
  Speaker Michael Turner (University of Chicago)
  Title Sakurai Prize Celebration "How many numbers does it take to determine our Universe?"
  Abstract Over the past three decades our understanding of the Universe has deepened.  The WMAP and Planck teams have asserted that just six numbers are needed to describe the whole Universe (fewer than the ten digits in a phone number), based upon their high-precision, all-sky maps of the Cosmic Microwave Background. Others have different opinions: one, two, a different six, and nine to determine our Universe. As I will discuss, the choice of numbers reveals much about what we know, our aspirations, and how we think about the Universe. After exploring the landscape, I will advocate for zero!
Host David Tanner

October 24
  Speaker James Fry (UF Physics)
  Title The 2019 Noble Prize in Physics - A Personal Perspective
  Abstract TBD
Host Hebard/Hirschfield

October 31
  Speaker Anupam Garg (Northwestern University)
Title "Magnets that find it hard to relax"
  Abstract Many processes in nature, such as alpha decay of U-238, or the conversion of ortho to para hydrogen, take place very slowly, and in each case, an investigation into the causes teaches us important physics. In this talk, we will discuss magnetic relaxation in single molecule magnets such as Fe8, which is also very slow, but for completely different reasons than the previous two examples.

At low temperatures, Fe8 displays spectacular quantum dynamics wherein the spin angular momentum degree of freedom of one molecule tunnels through 20 units of hbar, with a tunnel splitting of ~ 1 pico eV, or about 1kHz in frequency units. This splitting is about 106 times smaller than the energy bias on a typical molecule in Fe8 crystals due to the dipole-dipole interaction. As a result, tunneling is strongly inhibited by energy conservation, and essentially impossible. The overall relaxation of magnetization is thus exceptionally slow, and understanding it is a challenging problem in classical many-body physics.

We will describe the theoretical model for how we believe Fe8 relaxes, along with Monte Carlo simulations and kinetic equations for the spin and dipolar-field distributions. We apply these approaches to various experimental protocols. The agreement between simulations, kinetic equation, and experiments is very good in most respects, but not so good for ultra long times and ultra-slow phenomena. The problem of how an initially demagnetized sample can be magnetized is particularly interesting and still open, and entails a situation where the magnetization relaxes
Host Mark Meisel

November 7
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November 14

  Speaker Mark Dykman (Michigan State University)
  Title Physics of and with nonlinear oscillators
  Abstract Recent progress in nano- and micromechanics and the emergence of circuit quantum electrodynamics have brought forward the need to understand mesoscopic vibrational systems. Because these systems are small, nonlinearity and quantum and classical fluctuations play a significant role in their dynamics. We will discuss some consequences of the interplay of fluctuations and nonlinearity. Mesoscopic oscillators make it possible also to study physics far from thermal equilibrium in the well-characterized setting. Of particular interest in this respect is the Floquet dynamics, including the “time-crystal” effect in coupled nonlinear oscillators.
Host Yoonseok Lee

November 21

  Speaker Douglas Glenzinski (Fermi Lab)
  Title A Rare Opportunity - the Mu2e Experiment at Fermilab
  Abstract The muon, a heavy cousin of the electron, was discovered in 1936. Since that time they have only ever been observed to do one of two things: 1) interact with a nucleus, or 2) decay into an electron and two neutrinos. But a new experiment at Fermilab - the Mu2e experiment - is going to look for a third thing: a muon interacting with a nucleus to produce an electron and nothing else. This is a process that's predicted to occur very very rarely, maybe once every quadrillion muon decays, (or less!). But this very rare decay may hold the key to understanding physics at its most fundamental level. The Mu2e experiment is an ambitious endeavor whose goal is to observe this very rare decay for the first time - a discovery that could help reveal a new paradigm of particle physics. I will describe the experimental challenges, both in terms of detector technology and data analysis, involved in searching for such a subtle process.
Host Jacobo Konigsberg

December 12 - Special Candidate Colloquium
  Speaker Rasul Gazizulin (Institute for Space Astrophysics - CNRS, Universite Paris-Sud)
  Title On-chip Mechanical Thermometry Implemented in a Nuclear Demagnetization Cryostat
  Abstract We report on microwave optomechanics measurements performed on a nuclear demagnetization cryostat. We describe a method for accessing the on-chip temperature, building on the blue-detuned parametric instability and a standard microwave setup. The capabilities and sensitivity of the experimental arrangement are demonstrated with a very weakly coupled silicon-nitride doubly clamped beam mode of about 4 MHz and a niobium on-chip cavity resonating around 6 GHz. We report on an unstable intrinsic driving force in the coupled microwave-mechanical system acting on the mechanics that appears below typically 10 mK. The origin of this phenomenon remains unknown and deserves theoretical input.
Host


PHYSICS COLLOQUIUM SCHEDULE

Spring 2020
The Colloquia are in Room 1002 NPB on Thursday at 4:05 PM
Refreshments will be served starting at 3:15 PM in NPB 2205

Contact: A. Hebard afh@phys.ufl.edu)
Department of Physics Colloquium Committee:
Hebard (chair), Fulda, Matchev, Mitselmakher, Wang


January 9 Bob Schrieffer Memorial Colloquium

  Speaker Steve Kivelson (Stanford University)
  Title Some of Bob Schrieffer’s Other Great Contributions to Physics
  Abstract Abstract
  Host Peter Hirschfeld/Yuxuan Wang

January 16
  Speaker Faculty search candidates
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January 23
  Speaker Michael Johnson (Center for Astrophysics, Harvard University)
  Title Imaging the Shadow of a Supermassive Black Hole with the Event Horizon Telescope
  Abstract Using Very Long Baseline Interferometry at 1.3mm wavelength, the Event Horizon Telescope (EHT) Collaboration recently published the first images of a black hole. I will discuss the breakthroughs that made these images possible and their implications for our understanding of supermassive black holes. I will also describe the emerging capabilities of the EHT to study relativistic dynamics of accretion flows, to elucidate the role of magnetic fields in jet launching, and to enable precision tests of General Relativity. Finally, I will discuss the complex, fractal structure that is predicted to appear in higher resolution images of black holes, which enables a new type of telescope that could image thousands of supermassive black holes.
  Host Cliff Will

January 30
  Speaker Faculty search candidate: En Cai (Univ California San Francisco)
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  Host Steve Hagen

February 6
  Speaker Danny Caballero (Michigan State University)
  Title Supporting the integration of numerical computation in physics education
  Abstract Computation has revolutionized how modern science is done. Modern scientists use computational techniques to reduce mountains of data, to simulate impossible experiments, and to develop intuition about the behavior of complex systems. Much of the research completed by modern scientists would be impossible without the use of computation. And yet, while computation is a crucial tool of practicing scientists, most modern science curricula do not reflect its importance and utility. In this talk, I will discuss the urgent need to construct such curricula in physics and present research that investigates the challenges at a variety of all scales from the largest (institutional structures) to the smallest (studentunderstanding of a concept). I will discuss how the results of this research can be leveraged to facilitate the computational revolution in science education. This research will help us understand and develop institutional incentives, effective teaching practices, evidence-based course activities, and valid assessment tools. This work has been supported by Michigan State University’s CREATE for STEM Institute, the National Science Foundation (DUE-1431776, DUE-1504786, DUE-1524128, DRL-1741575, DRL-1812916), the Norwegian Agency for Quality Assurance in Education (NOKUT), the Norwegian Research Council, and the Thon Foundation.
  Host Shawn Weatherford

February 13
  Speaker Margaret Cheung (University of Houston)
  Title Proteins in a crowd under heat and pressure
  Abstract In order to function, many proteins fold into a well-packed structure, and yet the folded phase must remain sufficiently flexible. It is unclear how proteins satisfy these contradictory constraints, especially in the crowded environment of a cell. I will present the theoretical and computational work from my group, which is in collaboration with experimentalists from the Gruebele group, addressing this challenging issue. We propose that these properties can coexist by tuning where the protein operates within its temperature-pressure-crowding phase diagram. Phase diagrams may contain ‘critical points’ where the difference between any two phases disappears, such as when liquid and vapor water become indistinguishable. We show that a protein can also have such a critical point. The enzyme phosphoglycerate kinase (PGK), which is involved in producing the ‘energy molecule of the cell,’ turns out to have a very crowding-sensitive critical point, above which the protein forms new structures. To paint a complete picture of the critical point for this protein, we expand upon the conventional temperature-pressure folding phase diagram by adding a third dimension: the degree of crowding (or volume-exclusion) from surrounding macromolecules. From simulations, we observe an intricate phase diagram, which contains a critical point that moves to lower a temperature as the crowding increases. We complement our simulation results by deriving a new thermodynamic equation of state that includes the critical line in the entire 3-dimensional phase diagram. To test our computational model, we observe folding transitions of PGK by fluorescence experiments, which validate the predicted critical point behavior. Our findings suggest that being near a critical point at physiologic conditions would be advantageous for enzymatic function because a protein may sample widely different conformations without passing a costly thermodynamic barrier.
  Host Arthur Hebard

February 20
  Speaker Faculty search candidate: (New York University) Mirna Mihovilovic
  Title Cracking neural circuits of a simple brainHow do brains compute?
  Abstract The Drosophila (fruit fly) larva is a small, semi-transparent crawling organism with about 10,000 neurons, compared to 100 billion in humans and 100 million in mice. Despite this simplicity, the larva carries out information-processing tasks, including navigation – moving towards a favorable location based on information from its senses. A century of genetic work in Drosophila combined with recent innovations in protein engineering allow us to use light to directly activate specific neurons in the larva. For instance, we can engineer larvae with light-activable neurons in their “noses.” When presented with red light, these larvae perceive an odor and respond by attempting to find its source. Using sophisticated light patterns and analysis methods, we developed an assay that allowed us to quantify how the larva makes decisions based on multiple sources of sometimes conflicting information. Advances similar to the ones that allow us to activate neurons using light allow us to measure thought patterns using light microscopes. Because the larva is almost clear, it has been a long-standing goal to use a microscope to “read the larva’s mind” as it navigates its surroundings. However, the 3D brain movements generated by the larva’s complicated locomotion have prevented optical recording of neural activity in behaving larvae. We developed a two-photon microscope capable of tracking single neurons moving rapidly in 3D while monitoring their activity in real time without motion artifacts. To record from many neurons we added a second beam that scans the volume around the tracked neuron to enable motion-corrected volumetric imaging in a freely-behaving animal. This allowed us to image correlated activity of motor and pre-motor neurons from a significant portion of larva’s “spine” in a completely unrestrained crawling animal. I will use these techniques to follow information flow through the larva’s circuits during sensory-motor transformations and achieve a neuron-level understanding of how a simple brain implements fairly complex calculations.
  Host Steve Hagen

February 27
  Speaker Faculty meeting
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March 5
  Speaker APS meeting and spring break
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March 12
  Speaker Aasish Clerk (University of Chicago) - CANCELLED
  Title One-way quantum interactions for fun and profit
  Abstract The most common kinds of interactions in physics obey a basic kind of reciprocity: when two systems or particles interact, each one influences the other, and information flows in both directions. In this talk, I’ll discuss general methods for engineering interactions that break this symmetry, in a fully consistent quantum setting. These engineered “one-way” quantum interactions open up a host of unusual possibilities, from new methods for manipulating and processing quantum information, to new kinds of topological and many-body physics. I’ll introduce some of the basic theoretical ideas that underlie these unusual interactions, and connections to recent interest in “non-Hermitian” quantum systems. I’ll also discuss recent experimental implementations in quantum optomechanical systems and superconducting quantum circuits.
  Host Selman Hershfield

March 19

  Speaker David Wiese (Jet Propulsion Laboratories) - CANCELLED
  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 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 scientific highlights from the GRACE mission, discuss the health and status of the GRACE-FO mission along with early scientific results, and look to how we can improve knowledge of surface mass changes in the future.  Future improvements can come in the form of improved instrumentation as well as different observing system architectures that increase the space-time sampling characteristics.  Possibilities for fusion of satellite gravimetry data with other geodetic data types (GNSS and satellite altimetry) will additionally be discussed.
  Host Paul Fulda

March 26
  Speaker Reserved for faculty talk
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April 2
  Speaker Eduardo Fradkin (University of Illinois)- CANCELLED
Title TBD
Abstract TBD
Host Wang

April 9
  Speaker Paul Canfield (Iowa State University) - CANCELLED
  Title TBD
Abstract TBD
  Host James Hamlin

April 16
Speaker Jonathan Feng (University of California Irvine) - CANCELLED
  Title TBD
Abstract TBD
  Hosts Konstantin Matchev and Wei Xue