Department of Physics and Astronomy	Search

Seminars/Colloquia, Spring 2023

Unless noted otherwise, Tuesday Colloquia are at 4:00 PM, refreshments will be served 15 minutes before each colloquium.
Scheduling for additional seminars will vary.

Date/Place	Speaker	Title (and link to abstract)
Tue, Jan 24 Lewis 101	Social gathering Relax, chat, and enjoy some snacks!
Thur, Jan 26 Lewis 101	Giacomo Fragione Center for Interdisciplinary Exploration and Research in Astrophysics Northwestern University	Hierarchical Black Hole Mergers: A Multi-band Opportunity for Gravitational Waves
Tue, Jan 31 Lewis 101	Matthew Route Department of Physics and Astronomy University of Mississippi	Substellar Magnetism at Radio Wavelengths
Thur, Feb 2 Lewis 101	Michael Fausnaugh Kavli Institute for Astrophysics and Space Research Massachusetts Institute for Technology	Transient Science with TESS and Frontiers in Time Domain Astronomy
Tue, Feb 7 Lewis 101	Nicholas MacDonald Radio Astronomy/VLBI Group Max Planck Institute for Radio Astronomy	Blacks Holes, Relativistic Blazar Jets, and Global Very Long Baseline
Thur, Feb 9 Lewis 101	Nihan Pol Department of Physics and Astronomy Vanderbilt University	Exploring the Gravitational Wave Landscape with Pulsars
Tue, Feb 14 Lewis 101	Ayush Dhital, Aniket Khairnar Department of Physics and Astronomy University of Mississippi	Student Research Presentations
Thur, Feb 16 Lewis 101	Tiffany Lewis Astroparticle Physics Lab Goddard Space Flight Center	Building Blocks for Blazars
Thur, Feb 23 Lewis 101	Akshay Khadse, Nathan Hill Department of Physics and Astronomy University of Mississippi	Student Research Presentations
Tue, Feb 28 Lewis 101	Woodrow Shew Department of Physics University of Arkansas	Brain on the Edge: Phase Transitions and Criticality in Cerebral Cortex
Tue, March 7 Lewis 101	Alexey Petrov Department of Physics and Astronomy University of South Carolina	Marvelous Muons: Searching for New Physics with Bound States
Tue, March 14 Lewis 101	No Colloquium - Spring Break
Tue, March 21 Lewis 101	Zhongzhou Chen Department of Physics University of Central Florida	Towards a student-centered mastery-based online STEM learning environment
Tue, March 28 Lewis 101	Umberto Tamponi Researcher, Istituto Nazionale di Fisica Nucleare (INFN) Sezione di Torino	Quarkonium and the New Landscapes of QCD
Tue, April 4 Lewis 101	Breese Quinn Department of Physics and Astronomy University of Mississippi
Tue, April 11 Lewis 101	Yishu Wang Department of Materials Science and Engineering Department of Physics and Astronomy University of Tennessee, Knoxville	Quantum Liquids in Solids
Tue, April 18 Lewis 101	Kristin Lewis Project Director, Public Engagement American Association for the Advancement of Science	Life Outside Academia Through Science Communication
Tue, April 25 Lewis 101	Robyn Sanderson Department of Physics and Astronomy University of Pennsylvania Center for Computational Astrophysics, Flatiron Institute	Dynamical Tests of Dark Matter and Galaxy Formation Theories in the Milky Way
Tue, May 2 Lewis 101	Matthew Rudolph Department of Physics Syracuse University	Flavorful Physics
Tue, May 9	No colloquium - Final Exam Week
This page has been viewed 54706 times. The physics colloquium organizer is Jake Bennett This page is maintained by David Sanders Latest update: Wednesday, 29-Mar-2023 17:15:43 CDT

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Abstracts of Talks

Giacomo Fragione Center for Interdisciplinary Exploration and Research in Astrophysics Northwestern University Hierarchical Black Hole Mergers: A Multi-band Opportunity for Gravitational Waves With about a hundred binary black hole (BBH) mergers detected via gravitational wave (GW) emission, our understanding of the darkest objects in the Universe has seen unparalleled steps forward compared to previous decades. While most of the events are expected to consist of first-generation BHs formed from the collapse of massive stars, others might be of a second or higher generation, containing the remnants of previous BH mergers. A fundamental limit for hierarchical mergers comes from the recoil kick imparted to merger remnants, which could result in the ejection from the host star cluster. However, hierarchical mergers can build up massive BHs and even form intermediate-mass black holes if the host cluster is massive and dense enough, as in nuclear star clusters and the most massive globular clusters. With their distinctive signatures of higher masses and spins, hierarchical mergers offer an unprecedented opportunity to learn about the densest systems in our Universe and to shed light on the elusive population of intermediate-mass black holes. The next years may bring hundreds of detections from hierarchical mergers with multi-band events chirping from space-based to ground-based detectors, promising a spectacular range of new science from stellar evolution to cosmology.

Matthew Route Department of Physics and Astronomy University of Mississippi Substellar Magnetism at Radio Wavelengths; Lurking between low mass stars and exoplanets on the mass scale lie ultracool dwarfs, which share characteristics with both classes of objects. Perhaps some of the most surprising discoveries among ultracool dwarfs are thatthey host strong, kG-strength magnetic fields and are powerful radio-emitters, despite their exoplanet-like effective temperatures and neutral atmospheres. However, many unanswered questions remain regarding their magnetic activity, including what are thecharacteristics of their magnetic dynamos, what is the nature of the electrodynamic engine that triggers magnetic reconnection to accelerate radio-emitting electrons, and what is the origin of the emitting plasma. One intriguing theory is that their radioemissions may be triggered by scaled-down star-planet magnetic interactions. Radio observations present an unprecedented opportunity to probe brown dwarf magnetic activity, examine the characteristics and functioning of dynamos among fully-convective objects,and investigate the nature of exoplanet magnetism.

Michael Fausnaugh Kavli Institute for Astrophysics and Space Research Massachusetts Institute for Technology Transient Science with TESS and Frontiers in Time Domain Astronomy Modern sky surveys are observing large swaths of the sky each night, even while pushing to faster and faster time sampling. As a result, the number of supernovae and other transient astrophysical explosions discovered per year is growing at an exponential rate. At the same time, densely sampled light curves produced by these surveys are enabling new scientific investigations. I will discuss recent results in extragalactic astronomy that my team has produced using some of these new observing facilities, particularly The Transiting Exoplanet Survey Satellite (TESS). In particular, I will present TESS light curves of 300 Type Ia supernovae and our search for companion star interactions. I will also show how time domain monitoring data of actively accreting supermassive black holes (quasars) can be used to map material within a few hundred gravitational radii of the black hole. Finally, I will discuss applications of TESS for electromagnetic follow-up of gravitational wave events from the LIGO-Virgo-KAGRA network, and other prospects for observing exotic transient events over the next decade.

Nicholas MacDonald Radio Astronomy/VLBI Group Max Planck Institute for Radio Astronomy Blacks Holes, Relativistic Blazar Jets, and Global Very Long Baseline: Interferometry High Energy Astrophysics in the Roaring 20s Blazars are an extreme subclass of active galactic nuclei (AGN), in which an accreting supermassive black hole launches a powerful relativistic jet of magnetized plasma that is closely aligned to our line-of-sight. Blazar jets: (i) shine across the entire electromagnetic spectrum (from low-frequency radio waves to high-energy gamma-rays), (ii) exhibit dramatic flares (on time scales ranging from days to minutes), and (iii) dominate the high-energy extragalactic sky. Very long baseline interferometric (VLBI) arrays (such as phased ALMA and The Event Horizon Telescope) are capable of imaging the polarized synchrotron emission emanating from the innermost regions of relativistic blazar jets with unprecedented angular resolution and sensitivity. In particular, the linearly and circularly polarized synchrotron emission from blazar jets carry imprints of both the strength and orientation of the collimating magnetic field as well as the plasma content of the jet environment. In parallel to these advances in VLBI imaging, modern computational resources now support the execution of increasingly sophisticated 3D numerical jet simulations, from shock-in-jet/turbulence models, to relativistic magneto-hydrodynamic (RMHD) and particle-in-cell (PIC) plasma simulations. In this talk, I will present a new suite of relativistic jet simulations which study the synchrotron polarization produced by blobs of relativistic plasma passing through standing recollimation shocks in the jet. This is accomplished through the use of the PLUTO code in concert with polarized radiative transfer ray-tracing calculations computed using the RADMC-3D code. The physical implications of this synchrotron emission will be discussed and direct comparisons will be made to actual VLBI observations of relativistic blazar jets.

Nihan Pol Department of Physics and Astronomy Vanderbilt University Exploring the Gravitational Wave Landscape with Pulsars Pulsars, which are rapidly rotating neutron stars, are a unique celestial object that can serve as both source and detector of gravitational waves (GWs). In this talk, I will give an overview of how multi-messenger observations of binary pulsar systems can shed light on the population of these systems in our Galaxy and present methods for optimizing current radio pulsar searches to find ultra-compact binary pulsars that will be visible with LISA. Finally, I will describe how millisecond-period pulsars can be used to construct a GW detector that is sensitive to nano-hertz frequency GWs and present results from the latest, most sensitive search for these GWs and the expectations for these detectors in the next few years.

Student Research Presentations Graduate students in the Department of Physics and Astronomy will present brief reports on their ongoing research.

Tiffany Lewis Astroparticle Physics Lab Goddard Space Flight Center Building Blocks for Blazars This talk examines what that means from a variety of perspectives - the concept of cosmic scale, the components of the system, and the physical processes we think we observe, all to frame how I think about modeling them, and to set up how I think about future projects and their larger context. We begin by building up the concept of scale in the universe through the lense of light travel time for the purpose of defining blazar size and distance between galaxies. Then, we will explore the structure and characteristics of active galaxies before diving into the physics of blazar jets, how it is studied and some key findings about the importance of particle acceleration and the limitations of current multiwavelength observations. We will then examine a suggested direction for the field of astrophysics and some thoughts on programmatic balance among the suite of missions NASA will solicit over the coming decades.

Woodrow Shew Department of Physics University of Arkansas Brain on the Edge: Phase Transitions and Criticality in Cerebral Cortex When many neurons interact, complex collective brain dynamics emerge. When the interactions among neurons are altered (e.g. by chemicals that affect alertness), brain dynamics can undergo a phase transition, dramatically changing from an ordered phase to a disordered phase, similar to the collective behavior of water molecules when transitioning from liquid to gas phase. In this talk, I will introduce and provide historical context for a somewhat controversial hypothesis at the interface of physics and neuroscience and share our recent experiments and data analysis that help resolve the controversy. The hypothesis is that the awake cerebral cortex operates in a critical phase near a transition boundary between ordered and disordered dynamics. Some previous experiments support this hypothesis, but others seem to contradict it. Here I will show that proper consideration of coarse-graining the observable microscopic variables (spikes of neurons), zooming out to the macroscopic level, is essential to reveal critical dynamics in awake brains. Another way to interpret this result is that brain dynamics are very high-dimensional, but critical dynamics exist in a low-dimensional subspace (if you like linear algebra, you might enjoy this interpretation). I will strive to make this talk accessible to those with no expertise in neuroscience and almost no expertise in the physics of phase transitions.

Alexey Petrov Department of Physics and Astronomy University of South Carolina Marvelous Muons: Searching for New Physics with Bound States Indirect searches for New Physics are the searches for quantum effects of new particles that can be discovered by observing tiny deviations between theoretical predictions and experimental observations. I will discuss how physicists have been using bound muons to probe New Physics that is not reachable by direct searches at the Large Hadron Collider.

Zhongzhou Chen Department of Physics University of Central Florida Towards a Student-centered Mastery-based Online STEM Learning Environment In the majority of today's STEM courses, students “march forward” at a uniform pace over the semester, regardless of their current status and previous backgrounds. Instructors teach largely the same course repetitively, with few rigorous and effective tools to evaluate the effectiveness of instruction and make significant improvements. In the student-centered, mastery-based STEM online learning environment of the future, students can proceed at different pace based on their level of mastery and background, guided by frequent self-assessment and feedback. The instructor's role will be transitioned into a designer, making data driven learning design improvements to the course. My past efforts toward creating such a learning environment can be roughly divided into three stages. First, an early prototype of online mastery-based learning modules for University physics I, was created on the open-source platform of Obojobo by UCF Center for Distributed Learning. Second, students' learning strategy and learning behavior is identified from click-stream data, and visualized using learning analytics techniques such as process mining. Third, data informed improvements of instructional design were implemented as natural experiments and evaluated using analysis methods such as “differences in differences”. Finally, my latest research focuses on creating mastery-based assessments, by harnessing the power of AI to create large isomorphic assessment problem banks. This new type of exam can be administered asynchronously, allow infinite number of attempts, openly shared and collaboratively developed, and are essentially “Chegg proof”. They will serve as stable “anchor points” for mastery-based learning environments.

Umberto Tamponi Researcher, Istituto Nazionale di Fisica Nucleare (INFN) Sezione di Torino Instituto Nazionale di Fisica Nucleare Quarkonium and the New Landscapes of QCD This seminar aims to show you how quarkonium is an extraordinary tool to explore the behavior of a strongly-coupled theory, in this case quantum-chromodynamics (QCD), in its transition from the perturbative to the non-perturbative regime. Quarkonium is a family of states with mass between 3 and 10 GeV/c2 usually described as bound states of a heavy quark and its antiquark. In such systems a hierarchy of energy scales naturally emerges: from the soft, non-perturbative scale that controls the spectrum to the hard scale of the annihilations. At each of these scales we are now observing unexpected phenomena, all connected to the emergence of light degrees of freedom inside the heavy meson. In this seminar I will introduce the basic features of quarkonia, review the most important recent progresses in connection with our understanding of QCD in the non-perturbative regime and finally outline the future lines of research in this field, with a focus on the experimental facilities.

Breese Quinn Department of Physics and Astronomy University of Mississippi

Yishu Wang Department of Materials Science and Engineering Department of Physics and Astronomy University of Tennessee, Knoxville Quantum Liquids in Solids Quantum spin liquids have been long hypothesized to demonstrate macroscopic entanglement of emergent degrees of freedom. While verification of such quantum mechanical nature remains experimentally challenging, the research front of quantum spin liquids has been significantly transformed over the last decade, which is particularly leveraged by the modern development of neutron scattering and materials synthesis techniques. In this talk, I will give two examples of this motif. The first example studies classical spin ice Ho2Ti2O7 by our newly developed time-resolved neutron scattering technique in combination with broad-band SQUID magnetometry. The dynamical process of magnetic relaxation manifests time scales spanning over ten decades and reveals a thermal crossover between two distinct relaxation processes. The second example explores the prospect of quantum spin liquids in metallic systems. In an antiferromagnetic state formed by 5f-electrons, inelastic neutron spectrum documented non-magnon features of magnetic excitation continuum, which persists in the paramagnetic state and up to an energy scale twenty times larger than the ordering temperature. The combination of spectra obtained from three state-of-art spectrometers turns out to be essential to parse through complicated spin dynamics in the metallic environment.

Kristin Lewis Project Director, Public Engagement American Association for the Advancement of Science Life Outside Academia Through Science Communication Graduate students learn a number of transferable skills while completing their degree, but it's not always clear how to use those skills outside of academia. Through the lens of her post-degree career path, Kristin will share tips for seeking employment outside of the traditional academic route and highlight opportunities to use scientific skills in government, policy, and communication. She will provide particular insight into two AAAS fellowship opportunities, the Science & Technology Policy Fellowship and the Mass Media Science & Engineering Fellowship. Kristin Lewis is a project director at the American Association for the Advancement of Science and leads the AAAS Mass Media Science & Engineering Fellowship, co-led the AAAS IF/THEN Ambassadors project and facilitated Communicating Science workshops. Prior to joining AAAS in 2019, Kristin supported the development of the Fourth National Climate Assessment at the U.S. Global Change Research Program and was an AAAS Science and Technology Policy Fellow at NASA. She also served as a project analyst in capital project management at Independent Project Analysis. She holds a Ph.D. in Physics from the University of Michigan, and can often be seen on her bike in the streets or trails around D.C.

Robyn Sanderson Department of Physics and Astronomy University of Pennsylvania Center for Computational Astrophysics, Flatiron Institute Dynamical Tests of Dark Matter and Galaxy Formation Theories in the Milky Way The results of the Gaia astrometric mission have ushered in a new era of “precision Galactic dynamics”. Using this new phase-space map of Galactic stars with unprecedented volume and accuracy, we are beginning to obtain new insights into the dark matter distribution in our Galaxy as well as its formation history. Thanks to significant advances on the computational front, meanwhile, we can now compare these insights directly with, and test our modeling strategies on, simulations of Milky-Way-mass galaxies where the influence of baryons and the cosmological context on the dark matter structure are realistically taken into account. I will demonstrate how this convergence of new data and better models improves our understanding of the Milky Way's dark matter distribution, leading to better constraints on the nature of dark matter and insights into its role in the formation of galaxies large and small.

Matthew Rudolph Department of Physics Syracuse University Flavorful Physics The Standard Model of particle physics features three different flavors of otherwise similar particles with very different masses. But why three? And why do they have such large differences? This is just one of many mysteries about our universe. In the absence of direct evidence for new physics, precision measurements and indirect searches are important to point the way forward. One experiment with a broad program in this direction is LHCb at the Large Hadron Collider, which studies the decays of heavy quark hadrons and many more topics. In this talk I will discuss LHCb's results and future promise in the context of the broader search for new physics.