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James Bonifacio
Department of Physics
Case Western Reserve University
Giving the Graviton a Mass
In general relativity, the gravitational force is mediated by a massless spin-2 particle…the graviton. In fact, the structure of general relativity and
its interactions with other particles are largely fixed by this requirement. However, there are still many open questions about the behavior of gravity,
both at short and long distances, which motivates the exploration of theories that deform general relativity. One such question is whether the graviton in
our universe can have a small but nonzero mass. In this talk I will review some of the challenges and successes in constructing theories of massive
gravitons and discuss some recent experimental and theoretical results that constrain such theories.
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Shanti Bhushan
Mechanical Engineering
Mississippi State University
Computational Fluid Dynamics: Turbulence Modeling and Applications
Turbulence/transition modeling is a primary source of uncertainty in computational fluid dynamics, and this problem remains unsolved despite over one
hundred years of scientific research. The talk will focus on an overview of author's ongoing research in transition/turbulence modeling and applications.
The key modeling topics that will be discussed are: identification of transition onset marker for bypass transition; modeling subgrid scale energy
transfer using algebraic models; and potential of machine learning for turbulence modeling. The key application topic will focus on role of turbulence on:
growth of vortical structures for ship flows; heat transfer; structural deformation for shock boundary layer interaction; growth of rotor wake; and
propagation of acoustic waves. Some open question in transition/turbulence will also be emphasized.
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Dustin Madison
Department of Physics and Astronomy
West Virginia University
Advancing the Capabilities of Nanohertz Gravitational Wave Astronomy
After fifteen years of ongoing effort to precisely monitor the most stable millisecond pulsars known, the North American Nanohertz Observatory for
Gravitational Waves (NANOGrav) is poised, within the next five years, to detect gravitational waves (GWs) in an entirely unexplored range of frequencies.
The initial detection will be just the beginning of a sustained campaign to characterize the nanohertz GW sky. I will discuss important fundamental
features of the astrophysics underpinning and motivating NANOGrav's efforts and certain unavoidable shortcomings of pulsar timing array investigations. I
have a plan to ameliorate these shortcomings by synthesizing pulsar timing data and precise astrometric surveys from instruments such as the Gaia space
telescope, a program that could powerfully augment both the imminent and long-term scientific returns of nanohertz GW astronomy. Finally, I will discuss a
new and interesting way that astrometric measurements could enable the detection of GW memory, a theoretically important signal sought after by GW
astronomers across the frequency spectrum.
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Gregory Vieira
Department of Physics
Rhodes College
Patterned Nanoscale Magnetic Traps and Applications for Single- and Few-Molecule Experiments
Directed and controllable manipulation of fluid-borne entities is important for a wide range of applications such as cellular diagnostics and nano-scale
assembly. We present a multiplexed mechanism for manipulating microscopic magnetic particles in fluid on arrays of patterned magnetic disks or wires. This
mechanism allows for probing and manipulation of micro- and nano-scale objects and biological entities in near-native environments, offers the flexibility
to apply forces to large numbers of objects simultaneously, and is remotely tunable by application of weak magnetic fields. We illustrate several
applications of this technique in the regime of single or few molecules: toward single biomolecule detection, single cell nanoinjections, and remote
control of microtubules gliding on kinesin assays.
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Yuan Li
Department of Astronomy
University of California — Berkeley
Supermassive Black Hole Feedback in the Centers of Massive Galaxies and Galaxy Clusters
The centers of massive galaxies and galaxy clusters contain hot plasma that loses its energy rapidly through radiation of X-ray photons. The energy loss
is thought to be compensated for by the energy input from the supermassive black holes (SMBHs) in the centers of these systems, via a process often termed
as "AGN feedback". In this talk, I will review the state of the field, and discuss what we have learned from numerical simulations in the past few years,
including how AGN jets deposit their energy to the surrounding medium, and how they affect cooling and star formation. I will also talk about my recent
analysis of optical and ALMA observations of multiphase filaments in cluster centers, which not only improves our understanding of AGN feedback, but also
puts unprecedented constraints on microscopic transport processes in the weakly-collisional, magnetized intracluster plasma.
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Philip Cowperthwaite
Carnegie Observatory
Carnegie Institution for Science
Electromagnetic Follow-Up of Gravitational Wave Events in the Next Decade
The Advanced LIGO and Virgo (ALV) gravitational wave interferometers began their third observing run (O3) in April of 2019. Since then they have so far
reported the detection of over 30 gravitational wave candidates. While the majority of detected events are likely to be the merger of two stellar mass
black holes, several events have a better than 50% chance of containing at least one neutron star making them enticing targets for electromagnetic
follow-up. In this talk, I will review the state of follow-up efforts and discuss the observational campaigns for two of these events: S190425z and
S190814bv. To date, no credible electromagnetic counterparts have been identified for any of these events. Nevertheless, studying these follow-up efforts
can provide valuable insight into the difficulties of obtaining joint detections of gravitational waves and electromagnetic signals. I will discuss how we
can tackle these challenges with the next-generation of observational facilities set to come online in the 2020s.
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Daniel D'Orazio
Institute for Theory and Computation
Harvard University
Multi-Messenger and Multi-Band Interrogation of Compact-Object Binaries
Binary systems consisting of two compact objects span at least ten orders of magnitude in mass, from the neutron stars and stellar-mass black holes paired via binary stellar evolution or dynamical encounters, to the supermassive black holes that meet at the centers of galactic nuclei. Accordingly, these systems arise from an enormously diverse range of astrophysical environments. What they share is their potential role in generating luminous, high-energy electromagnetic radiation and their ability to generate detectable gravitational radiation upon merger. I will discuss work aimed at electromagnetically identifying a yet undetected population of sub-parsec separation supermassive black hole binaries, which are targets of ongoing monitoring by the pulsar timing arrays as well as the future LISA gravitational-wave observatory. I will also discuss work that leverages detection of gravitational waves in multiple frequency bands to elucidate the astrophysical origin of the LIGO gravitational-wave events. In the coming years, present and upcoming time domain surveys (e.g., the Vera C. Rubin Observatory) and gravitational-wave observatories (e.g., LISA, LIGO and its evolutions) will drive forward investigations of compact-object binaries across the mass scale, and drastically expand our knowledge of compact-object binary populations and the environments that shape them.
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Hsin-Yu Chen
Black Hole Initiative
Harvard University
Gravitational-wave Observations from Quarks to the Universe
Advanced LIGO-Virgo have detected tens of stellar mass compact binary mergers, including binary black holes, binary neutron stars, and potentially neutron star-black hole mergers. These binary merger detections carried plenty of information about the binaries and the Universe. In this talk I will focus on a few topics we learned from the gravitational-wave detections: the electromagnetic counterparts of binary mergers, the neutron star equation-of-state, and the expansion rate of the Universe. I will first summarize current status of the field and the future projections. I will then discuss future plans to expand and improve the study.
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Zheguang Zou
National Center for Physical Acoustics and Department of Physics and Astronomy
University of Mississippi
Three-Dimensional Seismic Oceanography in the Gulf of Mexico
Seismic oceanography is a new interdisciplinary science that uses legacy marine seismic data from the oil industry to image the ocean water column like eddies or oceanic internal waves. The imaging is achieved by acoustic signals emitted by air guns, reflected from the ocean, and collected by a hydrophone array towed by a ship. For a ship traveling in the ocean, the temperature-salinity structure of the water column can be imaged from the collected signals with a resolution much higher than traditional oceanography measurements.
Previous seismic oceanography studies are largely based on two-dimensional seismic images. However, the ocean by nature requires three-dimensional (3D) imaging with high resolution. This talk will report our recent results on the imaging of the temporal and spatial variation of water column fluctuations in the Gulf of Mexico enabled by 3D seismic oceanography.
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Jake Bennett
Department of Physics and Astronomy
University of Mississippi
High Energy Physics at Ole Miss
The Department of Physics and Astronomy at Ole Miss contributes to major theoretical and experimental efforts in high energy particle physics, including several international experiments. This colloquium will include an introduction to the field and a review of some of the HEP research ongoing at Ole Miss.
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Yun Jing
Graduate Program in Acoustics
Pennsylvania State University
Numerical Modeling of Medical Ultrasound
In the last two decades, we have witnessed enormous development in
high intensity focused ultrasound (HIFU) for treating a broad
spectrum of diseases and medical conditions. As a non-invasive
surgical modality that can reach deep tissue, HIFU has the potential
to revolutionize therapy. To truly understand, design and improve
HIFU-based technologies and eventually adopt them clinically, it is
vital to have a versatile and fast, yet accurate ultrasound
numerical model. Although there are many ultrasound numerical models
available, none can currently achieve both efficient and
sufficiently accurate simulations for acoustic wave propagation in
large-scale, heterogeneous biological media. Existing numerical
models face two enduring dilemmas: they are either very efficient
but not accurate due to invalid approximations, or they are very
accurate but computationally time-consuming and therefore
impractical in many cases. In this talk, I will discuss our effort
throughout the past 10 years in developing new numerical models for
HIFU, that aims to establish a balance between accuracy and
computational efficiency, therefore filling the gap between these
two critical requirements. I will focus on both the theoretical
development and the practical applications of the numerical
algorithm. I will also introduce our ongoing NIH-funded project that
aims to develop an open-source toolbox for modeling medical
ultrasound.
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Chen Shen
Electrical and Computer Engineering
Duke University;
Architected Materials: Next Generation Functional Acoustic
Materials
The recent development of functional materials has reshaped almost every aspect of our lives. In modern society, we are able to synthesize structures with properties beyond their constituent materials — referred to as architected materials. My research focuses on the study of architected materials, including their design, fabrication, and application in acoustics. In this talk, I will sample some of my contributions to this field. For instance, (1) I will show how reconfigurable architected materials lead to multifunctional acoustic devices. (2) I will demonstrate the design of highly efficient architected materials for acoustic wave control. (3) I will discuss the potential of architected materials through marriage with advanced manufacturing. At the end of the talk, I will showcase some of my ongoing work on architected materials for medical and ultrasound applications.
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Philip L. Marston
Department of Physics and Astronomy
Washington State University
Decades of Acoustical, Optical, & Fluid Wave Physics with Students & Associates
Following introductory comments concerning a Washington State College Physics MS degree recipient from 1928, selected research from four recent decades will be summarized. Some examples to be considered include the close relationship between optical and acoustical scattering research and the value of understanding short and long wavelength scattering processes. Novel forms of rainbow and glory scattering were discovered. In some cases waves can be simultaneously used to probe and control the shape and position of drops and bubbles and to stabilize liquid columns; investigations outside the laboratory included reduced-gravity aircraft and the Space Shuttle. Related developments concern radiation torque, vortex beams, and tractor beams. In other developments, lessons from short-wavelength scattering experiments were applied to acoustical situations having reduced symmetry, facilitating improved interpretation of acoustical images and signatures of objects in water. Participation of students and program alumni in acoustical field experiments for the remediation of unexploded ordnance (UXO) will be noted.
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Maarten Buijsman
School of Ocean Science and Engineering
University of Southern Mississippi
Giant Underwater Waves Mixing the Ocean's Waters
The ocean's interior is filled with giant waves that can only exist because the ocean is vertically stratified in temperature and salinity. Some of these waves are more than 300 feet tall and 100 miles long. Like waves at the ocean surface, internal waves are restored by gravity. These internal gravity waves are generated by wind, tides, and the slow ocean circulation. As internal waves propagate through the ocean, they interact with topography, the ocean circulation, and other internal waves, facilitating an energy cascade to smaller scales, and eventually turbulence. Like breaking waves on the beach, the turbulence of breaking internal waves mixes the water below the ocean's surface. This is relevant for the dispersion of sediments and nutrients, the general ocean circulation, and ultimately the earth's climate.
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Seth Pree
Department of Physics and Astronomy
University of California — Los Angeles
Acoustic Plasma Trapping and Plasma Thermoacoustics
An oven's worth of microwaves can be used to both make a few
thousand Kelvin plasma and cause that plasma to generate sound. Such a
system can be used as a tweeter, but the luminous plasma subjected to
its own sound field raises more interesting opportunities in both
nonlinear acoustics and thermoacoustics. For example, how can the sound
field established by modulating the microwave power lighting up a
ping-pong ball sized bulb containing 30 mg of sulfur trap the resulting
3000+ K plasma in the center of a spherical cavity? Continuous wave
(CW) microwaves may also be used to generate sound via the Sondhauss
effect in a Helmholtz resonator. I will end by presenting an
unconventional, 3D thermoacoustic gain mechanism based on the variation
in the plasma's conductivity due to the sound's adiabatic compression.
If realized, 3D plasma thermoacoustics may help addressing questions
about Cepheid variable stars.
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