The University of Mississippi
Department of Physics and Astronomy

Seminars/Colloquia, Spring 2016

Unless noted otherwise, Tuesday Colloquia are at 4:00 PM
with refreshments served 15 minutes before each colloquium.

Scheduling for additional seminars will vary.

Date/Place Speaker Title (and link to abstract)
Tue, Jan 26
Lewis 101
Don Summers
Department of Physics and Astronomy
University of Mississippi
Supernova 1987A: Death of a Star
Tue, Feb 2
Lewis 101
Don Summers
Department of Physics and Astronomy
University of Mississippi
Voyager: Mission to Jupiter, Saturn, Uranus, and Neptune
Tue, Feb 9
Lewis 101
Racha Cheaiab
Department of Physics
McGill University
Search for Rare B Meson Decays at the BaBar Experiment
Thur, Feb 11
9:15 AM

Lewis 101
Lucien Cremaldi
Department of Physics and Astronomy
University of Mississippi
Update on the Search for Gravitational Waves from LIGO
Tue, Feb 16
Lewis 101
Marco Cavaglià & Katherine Dooley
Department of Physics and Astronomy
University of Mississippi
Observation of Gravitational Waves from a Binary Black Hole Merger
Tue, Feb 23
Lewis 101
Kevin Beach, Luca Bombelli and Lucien Cremaldi
Department of Physics and Astronomy
University of Mississippi
Graduate Student Meeting
Tue, Mar 1
Lewis 101
Hajime Sotani
Division of Theoretical Astronomy
National Astronomical Observatory of Japan
Magnetic Oscillations in Neutron Stars
Tue, Mar 8
Lewis 101
Ken Bader
Department of Internal Medicine
University of Cincinnati
Mechanical Ablation of Tissue with Focused Ultrasound
Tue, Mar 15
Lewis 101
Spring Break
 
 
 
Tue, Mar 22
Lewis 101
Thomas Sotiriou
School of Physics & Astronomy
University of Nottingham
Black Holes Without Relativity
Tue, Mar 29
Lewis 101
Richard Brito
Gravitation in Técnico
Instituto Superior Técnico — CENTRA
Interaction Between Bosonic Fields and Compact Objects
Tue, Apr 5
Lewis 101
Pengfei Zhang
Department of Mathematics
University of Mississippi
Homoclinic Intersections for Geodesic Flows on Convex Spheres
Tue, Apr 12
Lewis 101
Greg Dooley
Kavli Institute for Astrophysics and Space Research
Massachusetts Institute of Technology
Tidal Stripping with Self-Interacting Dark Matter
Tue, Apr 19
Lewis 101
Alexander B. Yakovlev
Department of Electrical Engineering
University of Mississippi
Non-local Susceptibility of the Wire Medium in the Spatial Domain Considering Material Boundaries
Tue, Apr 26
Lewis 101
Ahmed Rashed
Department of Physics and Astronomy
University of Mississippi
Non-standard Tau Neutrino Interactions
Tue, May 3
Lewis 101
Kevin Beach, Luca Bombelli and Lucien Cremaldi
Department of Physics and Astronomy
University of Mississippi
Graduate Student Meeting
Tue, May 10
Lewis 101
Final Exam Week  

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Abstracts of Talks


Don Summers
Department of Physics and Astronomy
University of Mississippi

Supernova 1987A: Death of a Star

A DVD account of the discovery of the first nearby supernova explosion in 500 years by University of Toronto graduate student Ian Shelton at the Las Campanas Observatory in Chile. Supernovas allow the formation of terrestrial planets by ejecting heavy elements into interstellar space and provide a standard candle which astronomers use to measure distances to galaxies.


Don Summers
Department of Physics and Astronomy
University of Mississippi

Voyager: Mission to Jupiter, Saturn, Uranus, and Neptune

The Voyager 2 flyby spacecraft observed active sulphur volcanoes on Jupiter's moon Io, photographed spokes in Saturn's rings, measured the magnetic field of Uranus, and saw liquid nitrogen geysers on Neptune's moon Triton.


Racha Chouiab
Department of Physics
McGill University

Search for Rare B Meson Decays at the BaBar Experiment

The current understanding of the basic constituents of matter in our universe is embedded in the Standard Model (SM). This model has succeeded as a low energy effective theory. Yet, even with its high level of consistency with experimental measurements, many questions are left unanswered. This motivates the ongiong hunt for new physics. In this talk, I present the search for rare B meson decays, specifically flavour-changing neutral current (FCNC) processes. FCNC processes, such as B → K(*)+ where = e, μ, τ or ν, are highly suppressed in the Standard Model (SM), with a branching fraction ranging between 10-5 and 10-7. These rare decays are forbidden at tree level and can only occur at lowest order via 1-loop diagrams. B → K(*)+ thus provides a stringent test of the SM and a fertile ground for new physics searches. The BaBar experiment at the SLAC National Accelerator Laboratory has completed its data taking, with 424 fb-1 collected at the Υ(4S) resonance. Using data from the BaBar experiment, I present the latest results on the search for B → K(*)+, where = e, μ, τ or ν. Furthermore, the first search for B+ → K+τ+τ is presented, along with its current status and anticipated sensitivity.


Lucien Cremaldi
Department of Physics and Astronomy
University of Mississippi

Update on the Search for Gravitational Waves from LIGO

100 years after Einstein predicted the existence of gravitational waves, the National Science Foundation gathers scientists from Caltech, MIT, and the LIGO Scientific Collaboration to update the scientific community on efforts to detect them.

University of Mississippi students, faculty and staff, as well as science enthusiasts from the Oxford community, are invited to join a live viewing event at the auditorium of the Department of Physics and Astronomy on Thursday, February 11, 9:30 a.m., as the National Science Foundation brings together scientists from Caltech, MIT, and the Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration at the National Press Club in Washington, D.C. for a status report on the effort to detect gravitational waves — or ripples in the fabric of space time.

The live broadcast will begin at 9:30 a.m. in Lewis Hall, Rm. 101, preceded by a brief introduction by Dr. Lucien Cremaldi, Chair and Professor of Physics and Astronomy. Doors will open at 9:00 AM


Marco Cavaglià &Katherine Dooley
Department of Physics and Astronomy
University of Mississippi

Observation of Gravitational Waves from a Binary Black Hole Merger

Abstract: The LIGO Scientific Collaboration published a paper on Thursday, Feb. 11, 2016 announcing two discoveries: the first direct detection of gravitational waves and the observation of a binary black hole merger. This momentous achievement is the result of over 50 years of a worldwide effort to design and build a detector sensitive enough to measure these infinitesimally small distortions of spacetime that Einstein predicted should exist 100 years ago. Marco Cavaglia and Katherine Dooley, members of the LIGO team, will give a short presentation describing the results, followed by a Q&A session. LIGO's discovery marks the beginning of a new field of gravitational-wave astronomy.


Hajime Sotani
Division of Theoretical Astronomy
National Astronomical Observatory of Japan

Magnetic Oscillations in Neutron Stars

Oscillation spectra of neutron stars might tell us the interior information of neutron stars. After the discovery of quasi-periodic oscillations in giant flares observed from soft gamma repeaters, there are many attempts to explain these evidences in terms of crustal torsional oscillations and/or magnetic oscillations in neutron stars. These attempts move toward a deeper understanding of the magnetic oscillations in magnetized neutron stars. In this colloquium, I will talk about the importance of neutron star oscillations from the asteroseismologial point of view and show the previous results about magnetic oscillations as well as the open problems.


Ken Bader
Department of Internal Medicine
University of Cincinnati

Mechanical Ablation of Tissue with Focused Ultrasound

Histotripsy is a transcutaneous focused ultrasound therapy that ablates tissue through the mechanical oscillations of microbubbles, or cavitation. Preclinical studies have found histotripsy effective for the treatment of prostate pathologies, cancer, deep vein thrombosis, and congenital heart disease. In this talk, the forms of histotripsy and their ablative mechanisms will be modeled in silico, and image-guidance techniques for mechanical ablation will be discussed. An analytic model will be presented to predict the extent of the treatment zone. This analytic model can be used for treatment planning, and to aid the FDA in the development of regulatory standards for histotripsy. Image-guidance of histotripsy will be demonstrated with a new ultrasound imaging modality called passive cavitation imaging (PCI). Studies in a prostate phantom demonstrate that PCI correlates well with the width of the ablation zone, indicating PCI can be used as a predictive metricfor tissue ablation from histotripsy. Finally, PCI will be used to monitor cavitation when histotripsy is used in combination with a lytic agent to lyse clots in a model of deep vein thrombosis. A significant improvement was observed in the thrombolytic efficacy for the combination treatment over histotripsy alone, suggesting a synergistic effect between histotripsy and the lytic agent.


Thomas Sotiriou
School of Physics & Astronomy
University of Nottingham

Black Holes Without Relativity

Lorentz symmetry is central to the concept of a black hole, as it precludes superluminal motion. It is not obvious that one can even define what a black hole is if Lorentz symmetry is abandoned, so one might expect that any observational evidence supporting the existence of black holes will impose very stringent constraints on Lorentz violations. I will discuss some basic aspects of causality in theories that violate Lorentz symmetry and I will argue that, remarkably, the concept of a black hole survives in these theories. After defining the appropriate notion of black hole, I will explore their basic aspects and discuss how they differ from black holes in General Relativity.


Richard Brito
Gravitation in Técnico
Instituto Superior Técnico — CENTRA

Interaction Between Bosonic Fields and Compact Objects

Fundamental bosonic fields generically arise as possible dark matter candidates and in extensions of General Relativity, but are also a useful proxy for more complex interactions. In this talk I will discuss the rich phenomenology of fundamental bosonic fields around black holes and compact stars. In particular I will discuss: (i) the interaction of self-gravitating bosonic structures with compact stars; (ii) superradiant instabilities around black holes and how it can be used to constrain particle masses.


Pengfei Zhang
Department of Mathematics
University of Mississippi

Homoclinic Intersections for Geodesic Flows on Convex Spheres

Transverse homoclinic intersection was discovered by Poincare in the study of stability properties of periodic orbits of n-body problem. Poincare realized that this is a mechanism which not only destroys the stability of periodic orbits but also leads the existence of chaos in the phase space.

In this talk, we will study the geodesic flows on convex spheres. We show that, generically, every closed geodesic is either hyperbolic or irrationally elliptic. Moreover, every hyperbolic closed geodesic admits some transverse homoclinic intersection. Therefore, (everywhere) chaotic dynamics can happen generically on manifolds with simple/trivial topology.


Greg Dooley
Kavli Institute for Astrophysics and Space Research
Massachusetts Institute of Technology

Tidal Stripping with Self-Interacting Dark Matter

Self-interacting dark matter (SIDM) postulates that dark matter is not entirely collisionless, but self scatters at a low rate. By transforming dark matter halo cusps to cores, SIDM offers a solution to the “too big to fail” problem and cusp/core problem in the Milky Way and local field. Two classes of models exist, with velocity-independent and velocity-dependent cross sections. While tight constraints exist on velocity-independent models, constraining velocity-dependent models remain elusive. In this talk, I discuss the implications of both types of SIDM on the tidal disruption of satellite galaxies in a Milky Way-like host. While the total dark matter mass loss rate is not affected, stellar mass loss is enhanced due to lower binding energy in subhalo cores. I discuss the variables affecting the strength of the increased stellar mass loss rate, the effect on observables in the Milky Way, and where we need to look to further constrain or identify self-interacting dark matter.


Alexander B. Yakovlev
Department of Electrical Engineering
University of Mississippi

Non-local Susceptibility of the Wire Medium in the Spatial Domain Considering Material Boundaries

The interaction of electromagnetic waves and wire media has been of interest for many years, driven by applications utilizing artificial plasma, epsilon-near-zero materials, negative refraction, wave canalization and other uses. When the period of the wires is small compared to wavelength, the structure can be considered as a homogeneous (homogenized) medium. Early models of wire media neglected spatial dispersion of the homogenized material, but it has more recently been shown that non-local effects are very strong for wire media and often cannot be ignored.

In this work, we show that the non-local susceptibility for a nontranslationally invariant homogenized wire medium is, modulo a constant, given by a simple Green's function related to the material geometry. We also show that two previous methods for solving wave interaction problems for bounded wire media (wave expansion method and transport equation) are equivalent to each other, and to a third method involving particle reflection at the boundary. We discuss the importance of the dead layer or virtual interface, and find it to be analogous to the excitonic semiconductor case. Several examples are provided to clarify the material.


Ahmed Rashed
Department of Physics and Astronomy
University of Mississippi

Non-standard Tau Neutrino Interactions

We now know that neutrinos have masses and that there is a leptonic mixing matrix just as there is a quark mixing matrix. The existence of neutrino masses and mixing requires physics beyond the standard model (SM). Hence, it is not unexpected that neutrinos could have new interactions beyond the standard model, or non-standard interactions (NSI). The effects of NSI have been widely considered in neutrino phenomenology. Bounds have been set on the NSI parameters. I will discuss the impact of the NSI on the measurement of neutrino mixing parameters such as the atmospheric and reactor mixing angles, mass hierarchy, and CP violation. We include form factor effects in our calculations and find the deviation of the actual mixing angle from the measured one, assuming the standard model cross section, can be significant and can depend on the energy of the neutrino.

A key property of the SM gauge interactions is that they are lepton flavor universal. Evidence for violation of this property would be a clear sign of new physics (NP) beyond the SM. Recently, hints of lepton flavor non-universality emerged from B-meson decay channels observed in the BaBar and LHCb experiments. We proposed tests of lepton flavor non-universality in tau-neutrino scattering. Different models have been introduced in this study of which charged Higgs, W', and Leptoquark.