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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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Zhenhua Tian
Department of Aerospace Engineering
Mississippi State University
Integration of Acoustics and Smart Materials for Structural Health Monitoring and Noncontact Manipulation of Micro/Nano Objects
Structural health monitoring (SHM) that integrates smart sensors and advanced sensing systems for online damage diagnosis and prognosis is critical for ensuring the safety of aerospace structures. Acoustic tweezers, which use acoustic waves for non-contact manipulation of micro/nano objects, have recently raised great interest for biomedical applications. This talk will focus on the integration of acoustics and smart materials to address current challenges in SHM and acoustic tweezers. The first part of the talk is about SHM systems based on laser ultrasonics and fiber Bragg grating (FBG) ultrasonic sensing 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 focuses on dynamic acoustic tweezers based on 10's MHz surface acoustic waves (SAWs). The acoustic tweezers use a programmable array of interdigital transducers (IDTs) for the translation, patterning, and concentration of micro/nano objects. Potential applications include single-cell analysis, hemoglobin detection, and cell patterning.
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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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