Events

Xinyue Gong
Department of Physics and Astronomy
University of Mississippi

Hall Effect for Acoustic Waves Carrying Angular Momentum

Acoustic waves with a twisted wave front also carry angular momentum in addition to linear momentum,in analogy to optical and quantum fields. The law of refraction states that the direction of refracted light rays is normally in the plane of incidence as they propagate across a sharp interface. Nevertheless, the refraction law is not enough to describe the angular momentum carried by refracted beams. Refracted light beams carrying angular momentum have been observed to undergo a shift in the direction that is transverse to the plane of incidence, a phenomenon that was termed as optical Hall effect. Here we pursue the first experimental observation of Hall effects for acoustic waves that carry angular momentum. Our experiment exploits the more recently developed acoustic metasurface to manipulate the wave refraction. A theoretical calculation of the wave fields is also conducted to compare with the experimental measurements. The talk will present physics related to the phenomenon, our experimental setup, and preliminary results.

Guoqin Liu
Department of Physics and Astronomy
University of Mississippi

Modeling and Simulations of Capillary-Gravity Wave Transmission Through a Surface Piercing Barrier

Capillary-gravity waves are waves traveling on a fluid interface that are influenced by both the effects of surface tension and gravity. Interactions of capillary-gravity waves with boundaries in contact with a solid and air play an essential role in both fluid physics and fluid control techniques. Motion of the contact line at the three phase boundary (solid, liquid, and air) can influence the wave dynamics such as the wave frequency, damping, refraction, and transmission. Here we develop fluid dynamics modeling and numerical simulations to investigate the transmission of capillary-gravity waves through a surface piercing barrier under the effect of a pinned contact line. Our modeling is validated via a comparison with prior theory in ideal cases. We numerically reveal how the surface tension and contact lines affect the transmission in the realistic case for waves of different frequencies and barriers of different depths.

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Meeting ID: 919 282 27187

M. Mahbub Alam

Daffodil International University, Dhaka, Bangladesh
Effects of Viscosity on Effective Dynamic Properties

Recent theoretical and experimental findings demonstrate that as the particle concentration in a suspension increases, the effect of viscosity of the base fluid becomes more and more significant, thereby requiring to be taken into account when calculating effective properties of a suspension. Here, we employ a core-shell, self-consistent, effective medium model to derive analytical approximations for effective bulk-modulus and effective mass density for a suspension of solid elastic spheres. We incorporate the viscosity of the suspending fluid into the model through wave conversion phenomena, primarily between compressional and shear wave modes. The analytical approximations are explicit functions of particle volume fraction, dimensionless compressional and shear wave numbers, and scattering coefficients of a single sphere. The dependence of effective properties on frequency, particle size, volume fraction, and viscosity are also investigated numerically.

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Meeting ID: 919 282 27187

Suravinda Kospalage
Department of Physics and Astronomy
University of Mississippi

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Meeting ID: 919 282 27187

Dipangkar Dutta
Department of Physics and Astronomy
Mississippi State University

The Incredible Shrinking Proton and the Proton Radius Puzzle

For nearly half a century the charge radius of the proton had been obtained from measurements of the energy levels of the hydrogen atom or by scattering electrons from hydrogen atoms. Until recently the proton charge radius obtained from these two methods, agreed with one another within experimental uncertainties. In 2010 the proton charge radius was obtained for the first time by precisely measuring the energy levels of an exotic kind of hydrogen atom called muonic hydrogen. The charge radius of the proton obtained from muonic hydrogen was found to be significantly smaller than those obtained from regular hydrogen atoms. This was called the “proton charge radius puzzle” and led to a rush of experimental as well as theoretical efforts to understand whythe size of the proton appears to be different when measured in regular hydrogen vs. muonic hydrogen. Many physicists were excited by the possibility that the “puzzle” was an indication of a possible new force that acted differently on electrons and muons.

The Proton Charge Radius (PRad) experiment at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) was one such major new effort which used electron scattering from a regular hydrogen atom, but with several innovations that made it the highest precision electron scattering measurement. These innovative methods have allowed us to measure the size of the proton more precisely than it has been measured before using electron scattering. I will provide a brief review of the techniques used to measure the proton's size and introduce the “ proton radius puzzle”, and the world-wide effort to resolve this puzzle. I will discuss the PRad experiment, the new results from this experiment, the current status of the “puzzle” and future prospects.

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Meeting ID: 919 282 27187

Katerina Chatziioannou
Division of Physics, Mathematics and Astronomy
California Institute of Technology

Constraining the Neutron Star Equation of State with Gravitational Wave Signals

Detections of neutron stars in binaries through gravitational waves offer a novel way to probe the properties of extremely dense matter. In this talk I will describe the properties of the signals we have observed, what they have already taught us, and what we expect to learn in the future. I will also discuss how information from gravitational waves can be combined and compared against other astrophysical and terrestrial probes of neutron star matter to unveil to the properties of the most dense material objects that we know of.

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Meeting ID: 919 282 27187

Stefano Tognini
Nuclear Energy and Fuel Cycle Division
Oak Ridge National Laboratory

Celeritas: Bringing Exascale Computing to HEP Detector Simulation

Within the next decade experimental High Energy Physics (HEP) will (mostly) finish building its next generation of particle detectors. This includes upgrades to the Large Hadron Collider and its main experiments, and completing the Deep Underground Neutrino Experiment (DUNE). This new Era brings a myriad of challenges, many being on the computational front. As DOE consolidates its network of Leadership Computing Facilities (LCFs) with supercomputers capable of reaching Exaflops of processing power, it is fundamental to better integrate these LCFs with HEP computing workflows. In this talk I will provide an overview of computing in HEP and its many challenges, and present Celeritas, a novel GPU Monte Carlo particle transport code developed by researchers from ORNL, Fermilab, ANL, and BNL, that aims to close the gap between DOE's LCFs and HEP experiments.

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Meeting ID: 919 282 27187

Biswaranjan Behera
Department of Physics
Colorado State University

The Search for Sterile Neutrinos with the ICARUS Detector at Fermilab

The 476-ton active mass ICARUS T-600 liquid Argon Time Projection Chamber (LArTPC) was a pioneering development that became the template for neutrino and rare event detectors, including the massive next generation international Deep Underground Neutrino Experiment. It began operation in 2010 at the underground Gran Sasso National Laboratories and was transported to Fermilab in the US in 2017. To ameliorate the impact of shallow depth operation at Fermilab, the detector was enhanced with the addition of a new high granularity light detection system inside the LAr volume and an external cosmic ray tagging system. Currently in the final stages of commissioning, ICARUS is the largest LArTPC ever to operate in a neutrino beam. In this talk I will describe how ICARUS will resolve a long-standing neutrino anomaly that favors the existence of a new, non-interacting, "sterile" neutrino.

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Meeting ID: 919 282 27187

Erika Hamden
Department of Astronomy and Steward Observatory
University of Arizona

Building Your Own Ultraviolet Telescope

Why do galaxies look the way they do? How do galaxies interact with their environments? How does a star form? How does the environment around a new star impact the planets that form around it? These questions can all be answered by observations in the ultraviolet, a seriously neglected wavelength range. In this talk, I will discuss several space and sub-orbital UV telescopes that I am developing to answer the questions above, including FIREBall-2 (a balloon-borne UV spectrograph), Aspera (a NASA funded extreme UV SmallSat), and Hyperion (a FUV mission in development). I will also describe the importance of technology development in enabling these missions and the science they can achieve. Finally, I will argue that the best way to answer difficult science questions is to stop waiting for someone else to build your telescope.

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Meeting ID: 919 282 27187

Zhenhua Tian
Department of Aerospace Engineering
Mississippi State University

Leveraging Acoustics for Structural Health Monitoring and Noncontact Manipulation of Micro/Nano Objects

Acoustic waves carry both information and energy that allow them to inspect material defects as well as create invisible robotic hands (i.e., acoustic tweezers) capable of manipulating matter. This talk will cover my previous studies on leveraging acoustics for structural health monitoring (SHM) and noncontact manipulation of micro/nanoparticles. The first part of the talk is about SHM systems based on laser ultrasonics and ultrasonic arrays for rapid inspection of defects in aerospace structures, such as delamination in composites, disbonding in honeycomb sandwich panels, and corrosion in metal plates. The second part of my talk focuses on dynamic acoustic tweezers based on 10's MHz surface acoustic waves (SAWs). These SAW-based acoustic tweezers use a programmable array of interdigital transducers (IDTs) for the translation, patterning, and concentration of micro/nano objects. Their functions will be discussed with experimental examples, including (i) constructing diverse lattice-like patterns of micro/nanoparticles, (ii) manufacturing composites with patterned carbon nanotubes, and (iii) printing anisotropic tissues with aligned cells.

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Meeting ID: 919 282 27187

Prajwal Mohan Murthy
Department of Physics
University of Chicago

Search for the Neutron Electric Dipole Moment and "what next?"

Baryon asymmetry of the universe, i.e. the fact that much of the observed universe is made of matter as opposed to equal amounts of matter and anti-matter, demands violation of Charge-Parity (CP) symmetry. Yet, the amount of CP violation from the Standard Model of particle physics is insufficient to explain the baryon asymmetry of the universe. Observation of a non-zero permanent electric dipole moment (EDM) coupled to the spin of any sub-atomic particle, such as the neutron, is an indication of CP violation. Therefore, measuring the neutron EDM, is a key technique of getting a handle on the amount of CP violation. The neutron EDM from the standard model sources is so small that no experiment has thus far achieved the sensitivity required. Nonetheless, searches for the neutron EDM is an important method by which to test and constrain physics beyond the standard model. The neutron EDM has been measured since the 1940s and the sensitivity of the experiments has improved by over 8 orders of magnitude.

The most recent series of efforts were conducted at the Paul Scherrer Institute (PSI). This was a room temperature experiment employing the Ramsey technique of separated oscillating fields. These measurements used a 21 l storage chamber, in which ultracold neutrons were stored, and surrounded by 4 layers of mu-metal. Prior to 2006, the series of measurements at the Institut Laue-Langevin (ILL) culminated in the measurement of d_n < 3 × 10^-26 e.cm (90% C.L) [Phys. Rev. D 92, 092003 (2015)] over 5 years of data taking. The ILL apparatus was upgraded significantly with addition of: (i) 16 Cs-133 magnetometers to further characterize the magnetic field environment in the storage chamber, (ii) a new neutron detector system which could simultaneously count both the spin states of the neutron, and (iii) optimized coating inside the storage chamber to maximize the neutron density. The upgraded apparatus was moved to the Paul Scherrer Institute and independently achieved a measurement of d_n < 1.8 × 10^-26 e.cm (90% C.L) [Phys. Rev. Lett. 124, 081803 (2020)] in just 2 years of data taking. The PSI nEDM experiment has also been a source of rich physics program beyond the measurement of the nEDM. It has investigated neutron oscillation, provided input into neutron lifetime measurements, searched for axions, and tested Lorentz Invariance.

While the search for CPV EDM was first attempted in neutrons, searching for atomic EDM may be a more lucrative avenue, since multiple sources contribute to an atomic EDM, viz. nucleon EDM, nuclear Schiff moment, CP violating interactions between the electrons and the nuclei, and the nuclear MQM also contributes to the atomic EDM. Nuclear Schiff moment and nuclear MQM are significantly enhanced in quadrupole and octupole deformed nuclei. We will also discuss viable candidate isotopes which have maximally enhanced sensitivity to EDMs.

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https://olemiss.zoom.us/j/91928227187

Meeting ID: 919 282 27187

Department of Physics and Astronomy
University of Mississippi

Research Poster Session

Despite the pandemic, student researchers in the Department of Physics and Astronomy have continued to do some excellent work. In the spirit of scientific discourse, we will be holding a research poster session tomorrow, Thursday April 21 at 4 pm in front of Lewis Hall. Please join us to hear about ongoing research in the department, and maybe get some ideas for a new project!

The web page can be found here.

Vojtech Witzany
School of Mathematics and Statistics
University College Dublin

Action-angle Coordinates for Black Hole Geodesics

Action-angle (AA) coordinates are a traditional tool in celestial mechanics with roots as early as in the works of Johannes Kepler in 1609. In modern terms, AA coordinates amount to a particular spectral solution of the equations of motion of a given conservative system. As a result, they serve as an extremely convenient basis for further analytical computations. I will show how AA coordinates are constructed for black hole geodesics, and how that will be useful in various approximations to the relativistic two-body problem and binary inspirals (EOB, large mass ratio,...).

Hartmut Grote
Gravity Exploration Institute
Cardiff University

Quantum-Enhanced Interferometry for Dark Matter and Quantum Gravity Searches

Laser interferometry has revolutionized astronomy by introducing a new sense in the observation of the universe. We can now hear the ripples of space-time: gravitational waves. Moving beyond this 'application' of laser interferometry, in this talk I will give an overview of how ultra-precise laser interferometers can also be used to try to shed light on other mysteries of the universe. Namely the search for dark matter and the question of whether space-time is quantized at the smallest level.

Joe Rivest, Madusanka Abeykoon, Devesh Bhattarai
Department of Physics and Astronomy
University of Mississippi

Student Research Presentations

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

Sina Rostami, Santosh Bhandari, Quinn Campagna
Department of Physics and Astronomy
University of Mississippi

Student Research Presentations

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

Cecille Labuda
Department of Physics and Astronomy
University of Mississippi

Spatial Variation of the Ultrasonic Properties of Brain

Brain is inhomogeneous due to its composition of different tissue types (gray and white matter), anatomical structures (e.g. thalamus and cerebellum), and cavities in the brain (ventricles). These inhomogeneities lead to spatial variations in the ultrasonic properties of the organ. However, reporting on the spatial variation of the ultrasonic properties is limited in the literature. The spatial variation of the speed of sound, frequency slope of attenuation, attenuation and backscatter in brain tissue are presented here as two-dimensional maps. Tissue specimens were 1-cm thick slices of fixed sheep brain prepared from the coronal, sagittal and transverse anatomic planes. Ultrasonic measurements were performed using broadband transducers with center frequencies of 3.5, 5.0, 7.5, and 10 MHz. The spatial variation of these properties are clearly visualized and structures visible in the maps are consistent with the known morphologic features of the brain. White and gray matter appeared to be distinguishable in the images. The average values of the ultrasonic properties are consistent with published values.

There will be refreshments at 3:45 pm in Lewis 109.

Jeffrey Kleykamp and Luiz Prais
Department of Physics and Astronomy
University of Mississippi

Search for Non-Standard Interactions with Neutrino Oscillations at the NOvA Experiment

The phenomenon of neutrino oscillations provided the first evidence for the so-called Physics Beyond the Standard Model, and opened a window for several and interesting new investigations in the field of neutrino physics. Among the possibilities, Non-standard interactions (NSI) are an extension of the neutrino matter effect leading to a rich phenomenology, and are expected to modify the propagation of neutrinos through matter. The current open questions in the neutrino oscillation model rely heavily on how neutrinos interact with matter, to an extent that NSI could induce possible effects. The NOvA Experiment presents its first preliminary search for flavor-changing NSI in neutrino oscillations in the 810 km baseline as neutrinos cross the Earth's crust between the Near and Far Detectors.

There will be refreshments at 3:45 pm in Lewis 109.

Sadia Khalil
Senior Data Scientist
Caterpiller, Inc.

From Physicist to a Data Scientist: It's Never Too Late!

I am a senior data scientist at Caterpillar Inc, and I like to share my story of career transformation in the industry after more than a decade of research in the LHC experiments at the CERN. I like to tell you why a data scientist career is a highly desired profession for people with a STEM background, especially in Physics. I like to give some tips on how to build a professional network and a well-composed resume, coding techniques, soft skills, and a strong knowledge of the fundamentals of statistics.

There will be refreshments at 3:45 pm in Lewis 109. —

Michael Schatz
School of Physics and Center for Nonlinear Science
Georgia Institute of Technology

Forecasting Turbulence

Fluid turbulence is one of the greatest unsolved problems of classical physics (and the subject of a million dollar mathematical (Millenium) challenge). Centuries of research--including Leonardo da Vinci's observations of "la turbolenza" and the best efforts of numerous scientists (Heisenberg, Kelvin, Rayleigh, Sommerfeld, ...)--have failed to yield a tractable predictive theory. However, recent theoretical and computational advances have successfully linked recurring transient patterns (coherent structures) within turbulence to unstable solutions of the equations governing fluid flow (the Navier-Stokes equations). The solutions describing coherent structures provide a geometrical structure that guides the evolution of turbulence. We describe laboratory experiments where the geometry of key coherent structures is identified, thereby provided building blocks for describing the behavior of weakly turbulent flows.

There will be refreshments at 3:45 pm in Lewis 104. —

Alumni panel
Department of Physics and Astronomy graduates

Alumni Panel

Graduates of the University of Mississippi Department of Physics and Astronomy will discuss their career path following graduation, discuss some of the benefits that their degree brought them, and answer questions posed by students in attendance.

There will be refreshments at 3:45 pm in Lewis 104. —

Jan Strube
Physical and Computational Sciences Directorate
Pacific Northwest National Laboratory

Machine Learning in the Physical Sciences

Machine learning and artificial intelligence (AI) algorithms have become a part of everyday life, from recommendation systems to autonomous driving. In their basic form, machine learning algorithms have been used in high energy physics for well over two decades. Interpretability and uncertainty quantification are essential characteristics of scientific algorithms, unlike many use cases in the industry. The seminar will give a brief introduction to machine learning, deep learning, and artificial intelligence, review the state of the art of machine learning in physics, with a focus on high energy physics, and point out areas of opportunities for further development.

There will be refreshments at 3:45 pm in Lewis 104. —

Scott Hertel
Department of Physics
University of Massachusetts Amherst

Recent Progress Towards the Detection of Dark Matter

As you read this, you are immersed in a bath of particles beyond the Standard Model, so-called "dark matter" particles which make their presence felt (so far) only through gravitational effects at astrophysical scales. Discovering the properties of these particles (their mass, interactions with other particles, etc.) is one of the great challenges of 21st century physics. I will describe three complementary efforts which look for dark matter particles scattering off atoms in a laboratory setting: LZ, HeRALD, and SPICE. Each effort uses novel technologies to progress towards ever greater sensitivity to new physics and potentially unraveling this great mystery.

There will be refreshments at 3:45 pm in Lewis 104.

John Beggs
Department of Physics
Indiana University Bloomington

The Cortex and the Critical Point

Condensed matter physics provides a framework for understanding experiments on ensembles of neurons. Within this framework, cascades of activity among cortical neurons follow the same equations that govern avalanches in granular materials, complete with power laws, an exponent relation and a universal scaling function. These "neuronal avalanches" also show that the cerebral cortex operates near a critical point where many of its information processing functions are optimized, analogous to peaks in susceptibility and correlation length seen at a continuous phase transition. I will review progress in this field over the past 20 years and point to the new frontiers it has opened in human health and computing.

You can find Dr. Begg's new book The Cortex and the Critical Point at MIT press and on Amazon

There will be refreshments at 3:45 pm in Lewis 104.

Joon Sue Lee
Department of Physics and Astronomy
University of Tennessee Knoxville

Superconductor-Semiconductor Hybrid Systems for Quantum Devices

In superconductor-semiconductor hybrid systems, interfaces and junctions with minimal disorder are crucial for realizing quantum phenomena associated with induced superconductivity. Advances in developing transparent interfaces by molecular beam epitaxy and clean junctions by in-situ shadowing have resulted in enhanced features of superconducting proximity effect. These schemes of in-situ deposition and shadowing of superconductors can be applied to quantum devices based on 1D nanowires, selectively grown in-plane 1D wires, and 2D electron gases. In this talk, materials and devices prepared by in-situ deposition and shadowing will be demonstrated, and transport studies revealing hard superconducting gap, two-electron charging effect, and zero-bias conductance peaks will be discussed.

There will be refreshments at 3:45 pm in Lewis 104.

John Wise
Center for Relativistic Astrophysics, School of Physics
Georgia Institute of Technology

The First Stars, Black Holes, and Galaxies in the Universe

Cosmic structure forms hierarchically through smooth accretion and dark matter halo mergers. As a consequence, all galaxies are the product of the dozens of mergers over billions of years. However, one can ask, “What were the first stars and galaxies in the universe?” I will review the current state-of-the-art simulations of early galaxy formation, starting with the formation of the first stars, which are initially devoid of metals and are suggested to have a characteristic mass of tens of solar masses. I will present results from a suite of cosmological radiation hydrodynamics simulations that focus on the transition from the first stars to the first galaxies. Each simulation captures the radiative and chemical feedback from 10,000 first stars, leading to the formation of a 10⁷ solar mass galaxy only 500 million years after the Big Bang, that can now be tested against the latest observations from JWST. Last I will highlight how some of the earliest massive black holes form during these early epochs that could be the seeds of supermassive black holes that exist at the centers of all massive galaxies today.

There will be refreshments at 3:45 pm in Lewis 104.

Fernanda Psihas
Neutrino Division
Fermi National Accelerator Laboratory

Neutrino Physics with Deep Learning: Applications, Successes, and Lessons

Neutrino experiments study the least understood of the Standard Model particles by observing their direct interactions with matter or searching for ultra-rare signals. The study of neutrinos typically requires overcoming large backgrounds, elusive signals, and small statistics. The introduction of state-of-the-art machine learning tools to solve analysis tasks has made major impacts to these challenges in neutrino experiments across the board. Machine learning algorithms have become an integral tool of neutrino physics, and their development is of great importance to the capabilities of next generation experiments. An understanding of the roadblocks, both human and computational, and the challenges that still exist in the application of these techniques is critical to their proper and beneficial utilization for physics applications. Dr. Psihas will showcase applications to detector data analysis developed in the past few years and present the current status of machine learning applications for neutrino physics in terms of the challenges and opportunities that are at the intersection between these two fields.

There will be refreshments at 3:45 pm in Lewis 104.