The University of Mississippi
Department of Physics and Astronomy

Seminars/Colloquia, Spring 2024

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 23
Lewis 101
Cancelled due to delay in University start
Stay safe!
 
Tue, Jan 30
Lewis 101
Kevin Beach
Department of Physics and Astronomy
University of Mississippi
Layered graphene at the magic angle
Tue, Feb 6
Lewis 101
Joao Luis Ealo Cuello
Universidad del Valle
Fulbright Scholar - NCPA
Engineering structured acoustic fields to manipulate objects in air without touching them
Tue, Feb 13
Lewis 101
 
 
 
 
Mon, Feb 19
Lewis 109
Maciek Wielgus
Research scientist
Max Planck Institute for Radio Astronomy
News from the M87* black hole
Tue, Feb 20
Lewis 101
UM graduate students
Journal club discussion
Tue, Feb 27
Lewis 101
 
 
 
 
Tue, March 5
Lewis 101
Joana Kramer
Postdoctoral Research Associate
Los Alamos National Laboratory
Simulating the polarized emission from relativistic AGN jets across the electromagnetic spectrum
Tue, March 12
Lewis 101
No Colloquium - Spring Break
Tue, March 19
Lewis 101
Jeffery Chancellor
Department of Physics and Astronomy
Louisiana State University
 
Mon, March 25
Lewis 101
Anil Panta
Physics Data Scientist - Experimental Nuclear Physics
Thomas Jefferson National Accelerator Facility
My Journey to Data Scientist at Jefferson Lab
Thur, April 4
Lewis 101
Biplab Dey
Institute of Physics and Astronomy
Eotvos Lorand University
 
Tue, April 9
Lewis 101
Xinmai Yang
School of Mechanical Engineering
Kansas University
 
Tue, April 16
Lewis 101
Christopher Macias
Department of Physics
Yale University
 
Tue, April 23
Lewis 101
Theresa Levitt
Department of History
University of Mississippi
 
Tue, April 30
Lewis 101
Jared Yamaoka
Data scientist
Microsoft
 
Tue, May 7
No colloquium - Final Exam Week  

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The physics colloquium organizer is Jake Bennett
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Latest update: Friday, 23-Feb-2024 13:00:36 CST

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Abstracts of Talks

Kevin Beach
Department of Physics and Astronomy
University of Mississippi

Layered graphene at the magic angle

Graphene is a two-dimensional semi-metal with many unusual electronic and mechanical properties. Because of its linear dispersion (the famous Dirac cone) and the lack of flat bands near the Fermi level, electronic interactions do not destabilize the conventional ground state into some other correlated phase. But when layers of graphene are stacked, either in registry or with a relative twist angle, low-lying flat bands are formed, and new avenues for strong-interactions physics are opened up. It has been discovered experimentally that the bilayer system at a magic angle of 1.1o is superconducting, and there is evidence of other nontrivial insulating phases. This colloquium addresses recent efforts to investigate the magic angle system with large-scale numerical simulations.

Joao Luis Ealo Cuello
Universidad del Valle
Fulbright Scholar - NCPA

Engineering structured acoustic fields to manipulate objects in air without touching them

The controlled manipulation of objects without contact is of great interest in a wide variety of emerging applications in engineering, biomedicine, pharmaceutics, among others. This can be achieved in different ways depending on the properties of the objects to be manipulated and the surrounding medium. Different technologies are available for this purpose, including optical tweezers, dielectrophoresis, compressed air systems, magnetophoresis, and acoustic/ultrasonic transducers. This talk explores various possibilities for manipulating objects in the air by generating structured acoustic fields, including vortex beams and ultrasonic tweezers. Acoustic forces and moments emerge to achieve various manipulation scenarios, allowing not only suspending but also transferring angular/linear momentum to objects ranging from microscopic scales to dimensions much larger than the wavelength. Research results are presented on the generation of airborne acoustic vortices using different approaches: 1. self-demodulation, 2. ferroelectret-based active diffraction gratings, and 3. high-power vibrations at ultrasonic frequencies capable of transferring angular momentum to large objects. Theoretical and experimental results are also shown for trapping samples in stationary ultrasonic fields created using counter-propagating beams. Finally, polygonal active diffraction gratings (PADF) are introduced as a transducer design approach for the generation of three-dimensional acoustic lattices, with potential applications in the engineering of living materials.

Maciek Wielgus
Research scientist
Max Planck Institute for Radio Astronomy

News from the M87* black hole

In 2017 Event Horizon Telescope (EHT), a global array of radio telescopes, observed the giant supermassive black hole M87* in the center of the M87 galaxy. These observations resulted in the first image of a black hole resolved at the event horizon scale. We have now completed the analysis of the corresponding data, with results on total intensity (2019), linear polarization (2021), and circular polarization (2023). It is a good time to summarize and systematize what we have learned about black holes, accretion disks, and magnetic fields from the EHT observations. I will also discuss the most recent first EHT results from 2018 observations of M87*, allowing us to study the persistence and variability of the black hole shadow image.

Joana Kramer
Los Alamos National Laboratory

Simulating the polarized emission from relativistic AGN jets across the electromagnetic spectrum

Modern ray-tracing in (hybrid) relativistic magnetohydrodynamic (RMHD) jet simulations has brought forth answers to questions about one of the most energetic phenomena in the universe - the jets originating from the centers of active galactic nuclei (AGN). Our research of these objects aims to bridge the gap between numerical simulations and observed polarization. We focus on understanding how the morphology of the jet's synchrotron emission is influenced by the magnetic properties of the relativistic plasma within the jet stream. To achieve this, we compare observational very-long-baseline interferometric data with our RMHD simulations, allowing us to identify favoured intrinsic magnetic fields in Blazar sources. The latest version of the PLUTO code facilitates the study of a macro particle module, enabling to model the emission from relativistic jets across the entire electromagnetic spectrum. This new module incorporates physics related to radiative losses and diffusive shock acceleration, which are crucial source terms in correctly modeling synchrotron emission from AGN jets. To compute polarization using the RADMC-3D code, we directly calculate and interpolate the non-thermal particle attributes on a grid in the 3D space. The final set of polarized images include maps of the four Stokes parameters (I, Q, U, and V) and linearly polarized intensity. The synthetic polarization maps are expected to provide valuable insights into the high-energy synchrotron polarization levels that NASA's Imaging X-ray Polarimetry Explorer (IXPE) mission is detecting in AGN sources. Our ultimate goal is to create a comprehensive simulation of the synchrotron spectral energy distribution (SED) of AGN, spanning from radio to X-ray. We analyze this SED over time, considering various jet simulation scenarios, including high-energy flares and environmental interactions.

Anil Panta
Physics Data Scientist - Experimental Nuclear Physics
Thomas Jefferson National Accelerator Facility

My Journey to Data Scientist at Jefferson Lab

In this talk, I'll tell you about my career path, explaining how the skills I gained from my Particle Physics PhD help me as a Data Scientist at JLab. I'll also share some projects I've started at JLab. My goal is to share my experience and provide insights to upcoming scientists who want to pursue a career in data science.