|
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.
|
|
Kei Nagai
Department of Physics and Materials Science
University of Memphis
Experimental Insights into Proton Structure
The proton, one of the basic building blocks of matter, still
holds many mysteries. It is made of quarks, antiquarks, and
gluons, which are bound together by the strong force. Although
scientists have long studied how these particles share the
proton's momentum, many details of their internal motion remain
unknown. Traditional measurements have focused on one-dimensional
quantities called parton distribution functions (PDFs), which
describe how the proton's momentum is divided among its
constituents. These measurements have revealed much about the
proton, but they cannot show the full picture of its internal
dynamics. Recent experiments are now also exploring
multidimensional structure functions that capture how quarks and
gluons move and interact inside the proton. This new approach is
helping us gain a deeper understanding of quantum chromodynamics
(QCD), the theory of the strong force, and may eventually explain
several open questions in nuclear physics. In this seminar, I
will introduce the basic ideas behind nuclear and particle
physics and explain how modern experiments are uncovering the
structure of the proton.
|
