The University of Mississippi
Department of Physics and Astronomy

Seminars/Colloquia, Fall 2025

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, Aug 26
Lewis 101
Department Social
Department of Physics and Astronomy
University of Mississippi
Ice Cream Social
Tue, Sep 2
Lewis 101
Yi Hua
The Vision Laboratory
University of Mississippi
Physics Meets Vision: Imaging and Computational Modeling of the Optic Nerve Head
Tue, Sep 9
Lewis 101
Alexander Plavin
Black Hole Initiative
Harvard University
Active Galaxies as Particle Accelerators: the Multimessenger View
Tue, Sep 16
Lewis 101
Tiffany Lewis
Department of Physics
Michigan Technological University
On the Importance of Accurate Particle Spectra in Multiwavelength Blazar Analysis
Tue, Sep 23
Lewis 101
Ignacio Taboada
School of Physics
Georgia Institute of Technology
IceCube and the Birth of High-Energy Neutrino Astrophysics
Tue, Sep 30
Lewis 101
Student Research Presentations
Department of Physics and Astronomy
University of Mississippi
Elizabeth B. Goreth: Fluids in Motion REU: Monitoring and Modeling Orphan Flares in Blazars
Aiden Collura: Numerical Simulation of Particle Orbits in Schwarzschild Spacetime
Anisa Jamal: Optimizing Particle Tracking Settings for Reliable Shear Wave Speed Analysis in Viscoelastic Micellar Fluids
Wells Valliant: Search for the Rare Decay Ξc+ to Λc+π0
Tue, Oct 7
Lewis 101
Kenichi Nishikawa
Department of Physics, Chemistry, and Mathematics
Alabama A&M University
3D PIC Simulations for Relativistic Jets with a Toroidal Magnetic Field and Associated Synthetic Spectra and Polarizations
Tue, Oct 14
Lewis 101
Francisco Sanchez
Department of Physics and Materials Science
University of Memphis
Studying AGN feedback under the microscope with Keck Adaptive Optics and JWST
Tue, Oct 21
Lewis 101
Quantum Movie Night
 
 
 
Tue, Oct 28
Lewis 101
Kei Nagai;
Department of Physics and Materials Science
University of Memphis
 
Tue, Nov 4
Lewis 101
Helvi Witek
Department of Physics
University of Illinois Urbana—Champaign
 
Tue, Nov 11
Lewis 101
Michel Villanueva
Physics Department
Brookhaven National Laboratory
 
Tue, Nov 18
Lewis 101
Matthias Kaminski
Department of Physics and Astronomy
University of Alabama
 
Tue, Nov 25
Lewis 101
Thanksgiving Break  
Tue, Dec 2
Lewis 101

Michela Negro
Department of Physics & Astronomy
Louisiana State University

 
Tue, Dec 9
Lewis 101
Final Exam Week  

This page has been viewed 69489 times.
The physics colloquium organizer is Nicholas MacDonald
This page is maintained by David Sanders
Latest update: Friday, 03-Oct-2025 13:59:32 CDT

Past semesters: 

Abstracts of Talks


Yi Hua
The Vision Laboratory
University of Mississippi

Physics Meets Vision: Imaging and Computational Modeling of the Optic Nerve Head

Glaucoma is a leading cause of irreversible blindness worldwide, driven by the progressive degeneration of retinal ganglion cell axons. This degeneration originates in a structurally complex region at the back of the eye known as the optic nerve head. While elevated intraocular pressure is the most prominent risk factor, the precise mechanisms by which mechanical loading leads to axonal damage remain poorly understood. In this talk, I will present how we integrate advanced imaging with physics-based computational modeling to investigate two leading hypotheses for how pressure contributes to retinal ganglion cell damage in glaucoma. These approaches allow us to visualize tissue-scale deformations, quantify microstructural changes, and simulate the biomechanics and hemodynamics of the optic nerve head under varying pressure conditions. By linking mechanics to neurodegeneration, our work seeks to provide new insights into the biophysical pathways of disease. A deeper understanding of these mechanisms is essential not only for advancing fundamental knowledge in ocular biomechanics but also for developing improved methods for early diagnosis and treatment strategies that can preserve vision..


Alexander Plavin
Black Hole Initiative
Harvard University

Active Galaxies as Particle Accelerators: the Multimessenger View

Astronomy has been solely relying on electromagnetic waves for centuries, until recent decades brought new messengers. These include high-energy neutrinos detected by specialized observatories — IceCube, KM3NeT, Baikal-GVD. Neutrinos have been associated with distant active galaxies, quasars, since 2017: initially in terms of individual objects, then with well-defined source samples. In this talk, I will present recent observational discoveries shedding light on neutrino origins in quasars. I'll discuss how they challenge the current models of quasars and particle acceleration in their centers. These objects appear to accelerate heavy particles even more efficiently than previously expected. Our understanding of cosmic particle accelerators still has many gaps, and I will outline how current and future instruments can fill them.


Tiffany Lewis
Department of Physics
Michigan Technological University

On the Importance of Accurate Particle Spectra in Multiwavelength Blazar Analysis

Blazars are active galaxies that produce the largest and most energetic sustained jets in the Universe. These jets are launched from the vicinity of supermassive black holes, but the exact processes are poorly understood. In order to connect the energy output in the jet with the available energy from the central engine, we need an accurate accounting of the energy of particles that produce observable electromagnetic radiation in the jet, even though we usually do not observe those particles directly. In recent work, my group demonstrates that not only should we include synchrotron and Compton losses in a particle model, but synchrotron self-Compton as well. Even for a flat spectrum radio quasar, where the synchrotron self-Compton process is subdominant, the amount of energy it costs the particles to produce that radiation is significant, and impacts our understanding of energy requirements from the central engine. Particle distribution simulations also lend themselves to estimates of neutrino production that may be significant to Ice Cube blazars and candidates. These theoretical simulations can be compared with archival data, but are also important to planning observations for upcoming facilities like COSI, which will observe MeV polarization, and SWGO, with which we hope to observe many more TeV blazars in the Southern Hemisphere.


Ignacio Taboada
School of Physics
Georgia Institute of Technology

IceCube and the Birth of High-Energy Neutrino Astrophysics

The IceCube Neutrino Observatory instruments a cubic kilometer of Antarctic ice to explore the Universe through >TeV ( 1012 eV) neutrinos. Completed in 2011, IceCube continuously monitors the entire sky (4π sr) with over 99% uptime. In this presentation, I will highlight IceCube's major scientific achievements: the discovery of an all-sky flux of extragalactic neutrinos, the detection of neutrinos from the Milky Way, and evidence for astrophysical point sources, including the Seyfert 2 galaxy NGC 1068 and the blazar TXS 0506+056. I will also discuss ongoing work by the Georgia Tech group to extend astrophysical neutrino observations down to energies as low as 10 GeV (1010 eV) and conclude with a forward-looking perspective on this new field over the next decade.


Elizabeth B. Goreth
Department of Physics and Astronomy
University of Mississippi

Fluids in Motion REU: Monitoring and Modeling Orphan Flares in Blazars

Blazars shine across the entire electromagnetic spectrum (from low-frequency radio waves to high-energy gamma-rays). There are a growing number of Blazar jets which exhibit Orphan gamma-ray flares (with little or no variability detected at longer wavelengths including the optical). The Ole Miss Blazar Group has recently established a new partnership with the Boston University (BU) Blazar Group to extend optical polarimetric monitoring of a sample of gamma-ray bright Blazars targeted by NASA's Imaging X- ray Polarimetry Explorer (IXPE). My REU project aimed to examine the Blazar 3C 120, which has recently entered a period of Orphan gamma-ray flaring. Using the BLAZE code (MacDonald et al. 2015, 2017), I am currently carrying out inverse-Compton calculations of gamma-ray emission to mimic the high-energy variability observed in 3C 120. I will present the results of my modeling efforts during the REU Research Program. In addition, as a member of The Ole Miss Blazar Group, I have been actively helping to monitor optical polarization in the BU Blazar sample and have made several trips to the Perkins Telescope Observatory (PTO) in Flagstaff, Arizona. The data we obtain at the PTO is crucial in ascertaining whether gamma-ray Blazar flares detected by the Fermi Gamma-ray Space Telescope are indeed Orphan in nature.


Aiden Collura
Department of Physics and Astronomy
University of Mississippi

Numerical Simulation of Particle Orbits in Schwarzschild Spacetime

In this project, I numerically simulated the motion of particles around a Schwarzschild black hole using the geodesic equations of general relativity. The goal was to explore how spacetime curvature affects the possible trajectories of massive particles. Including stable orbits, flybys, and falling into the black hole. By implementing these equations in Mathematica and using numerical integration techniques, I was able to visualize how extremely sensitive particle motion is near such an object. This work helped me gain a deeper understanding of general relativity, geodesics, and the behavior of matter in curved spacetime.


Anisa Jamal
Department of Physics and Astronomy
University of Mississippi

Optimizing Particle Tracking Settings for Reliable Shear Wave Speed Analysis in Viscoelastic Micellar Fluids

This experiment focused on optimizing particle-tracking parameters to enable accurate measurement of shear wave properties in a high-concentration CTAB-NaSal micellar fluid seeded with microspheres. Shear waves were generated using a mechanical wave driver, and their propagation was recorded with a high-speed camera. Video data were processed to track the trajectories of the microspheres. Particle-tracking parameters were optimized by trial and error to obtain better particle trajectories. Tracking quality was highly sensitive to input parameters. Improper settings introduced noise, false trajectories, or out-of-phase particle motion, whereas optimized values yielded cleaner and more reliable results. Specifically, adjusting displacement and link range accounted for frame-to-frame motion at different frequencies, while refining percentile thresholds minimized false detections. With these optimized settings, in-phase particle trajectories were successfully isolated, allowing improved determination of wavelength as the vertical spacing between such particles. Combining wavelength with the known driving frequency enabled calculation of shear wave speed. This study demonstrates that parameter optimization is essential for determining reliable physical measurements, such as that shear wave speed in viscoelastic micellar fluids.


Wells Valliant
Department of Physics and Astronomy
University of Mississippi

Search for the Rare Decay Ξc+ to Λc+π0

The Belle II experiment at the SuperKEKB accelerator facility in Japan is designed to study rare and suppressed decays to search for new physics. We present a study of Ξc+ decays to Λc+π0 using Belle II simulation. The photons emitted from the π0decay have very low energy, leading to a very high background. To isolate the decay of interest from this large background, we employed machine learning techniques to optimize event selection criteria. The results of this study lay a foundation for future measurements with experimental data.


Kenichi Nishikawa
Department of Physics, Chemistry, and Mathematics
Alabama A&M University

3D PIC Simulations for Relativistic Jets with a Toroidal Magnetic Field and Associated Synthetic Spectra and Polarizations

Particle-in-Cell simulations can provide a possible answer to an important key issue of astrophysical plasma jets, i.e., how a toroidal magnetic field affects the evolution of pair and electron-ion jets associated to the acceleration of particles. We show that Weibel, mushroom, and kinetic Kelvin-Helmholtz instabilities excited at the linear stage, generate a quasi-steady electric field component along the jet, which accelerates and decelerates electrons. We find that the two different jet compositions (pair and electron-ion) generate different instability modes respectively and observe significant differences in the structure of the strong electromagnetic fields that are driven by the kinetic instabilities with the pair jet. Moreover, the magnetic field in the non-linear stage generated by different instabilities is dissipated and reorganized into new topologies. A 3D magnetic field topology depiction indicates possible reconnection sites in the non-linear stage where the particles are significantly accelerated by the dissipation of the magnetic field associated to a possible reconnection manifestation.


Francisco Sanchez
Department of Physics and Materials Science
University of Memphis

Studying AGN feedback under the microscope with Keck Adaptive Optics and JWST

The discovery of several black hole scaling relationships has shown that supermassive black holes are not just astronomical ornaments sitting at the centers of galaxies, but they play a crucial role in the formation and evolution of galaxies. In this talk, I will describe recent work showing how supermassive black holes influence their host galaxies. I will focus on our team's recent results for a large sample of nearby active galactic nuclei (AGN) observed with Adaptive Optics (AO) at the Keck Observatory (the KONA survey) and with JWST. Our sample contains AGN in isolated galaxies and AGN pairs. We find that AGN-driven outflows of ionized gas are ubiquitous in both, single and dual AGN, with mass outflow rates ranging from a few solar masses per year in Seyfert galaxies to ~100 solar masses per year in dual AGN. The observations provide direct evidence of the ways in which the AGN outflows interact with the interstellar medium (AGN feedback in action), either by creating cavities of molecular gas, or by launching molecular outflows, in both cases suppressing star formation.