The University of Mississippi
Department of Physics and Astronomy

Seminars/Colloquia, Spring 2017

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 24
Lewis 101
Hartmut Grote
Division of Laser Interferometry and Gravitational Wave Astronomy
Albert Einstein Institute — Hannover, Germany
The Physics of Climate, the IPCC, and the Public Discourse:
A Tour D'Horizon of Global Warming
Tue, Jan 31
Lewis 101
No Colloquium
 
 
(Graduate Student Comprehensive Examinations)
Tue, Feb 7
Lewis 101
Mauricio Richartz
Centro de Matemática
Universidade Federal do ABC — Brazil
Analogue Black Holes: Theory and Experiments
Tue, Feb 14
Lewis 101
 
 
 
 
Tue, Feb 21
Lewis 101
Maarten Buijsman
Division of Marine Science
University of Southern Mississippi
The Equatorial Pacific "Graveyard" for Semidiurnal Internal Tides: Incoherence or Dissipation?
Fri, Mar 3
Lewis 101
Carlos Herdeiro
Departamento de Física
Universidade de Aveiro — Portugal
Can a Black Hole Have Hair?
Tue, Mar 7
Lewis 101
Seth Hopper, Laura Bernard, Andrea Nerozzi
Gravitation in Técnico
Instituto Superior Técnico — Portugal
Bound and Unbound Motion Around Static Black Holes(Seth Hopper)
Gravity
Tue, Mar 14
Lewis 101
Spring Break
 
 
 
Tue, Mar 21
Lewis 101
Sabrina Savage
Science Research Office
Marshall Space Flight Center
Solar Flares
Tue, Mar 28
Lewis 101
 
 
 
 
Tue, Apr 4
Lewis 101
 
 
 
 
Tue, Apr 11
Lewis 101
 
 
 
 
Tue, Apr 18
Lewis 101
Tanaz A. Mohayai
Department of Physics
Illinois Institute of Technology
Measurements Of Beam Cooling In Muon Ionization Cooling Experiment
Tue, Apr 25
Lewis 101
Guido Mueller
Department of Physics
University of Florida
LISA Pathfinder
Tue, May 2
Lewis 101
Bevin Etienne
McIntire School of Commerce
University of Virginia
Wind Turbines
Tue, May 9
Lewis 101
Final Exam Week  

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Abstracts of Talks


Hartmut Grote
Division of Laser Interferometry and Gravitational Wave Astronomy
Albert Einstein Institute — Hannover, Germany

The Physics of Climate, the IPCC, and the Public Discourse: A Tour D'Horizon of Global Warming

Global warming is a topic of broad scientific inquiry as well as societal relevance. I will review the basic principles of climate physics, explain the role of the IPCC in assessing different aspects of global warming, and will try to shed some light on the public discourse around global warming and forces trying to obstruct the science.


Mauricio Richartz
Centro de Matemática
Universidade Federal do ABC — Brazil

Analogue Black Holes: Theory and Experiments

Analogue models of gravity, introduced by Unruh in 1981, have been (for some time now) very helpful towards a better theoretical understanding of several crucial phenomena at the boundary of gravity and quantum field theory. Experimental research on analogue models, however, started only very recently. In this talk, I will explain the basic theory behind analogue models of gravity and how they can be used to mimick important quantum field theory effects in curved spacetimes, like Hawking radiation. I will also focus on some experimental realizations of analogue models of gravity, including one based on surface waves propagating on water. which I have been involved with very recently (arXiv: 1612.06180).


Maarten Buijsman
Division of Marine Science
University of Southern Mississippi

The Equatorial Pacific "Graveyard" for Semidiurnal Internal Tides: Incoherence or Dissipation?

The jets in the equatorial Pacific Ocean of a realistically-forced global circulation model with a horizontal resolution of 1/12.5 degree yield a strong loss of phase coherence in semidiurnal internal tides that propagate equatorward from the French Polynesian Islands and Hawaii. This loss of coherence is determined with a baroclinic energy analysis, in which the semidiurnal-band terms are separated into coherent, incoherent, and cross terms. For time scales longer than a year the coherent energy flux approaches zero values at the equator, while the total flux is 500 W/m. The time-variability of the incoherent energy flux is compared with phase speed variability computed with the Taylor-Goldstein equations. The variability of monthly-mean Taylor-Goldstein phase speeds agrees well with the phase speed variability inferred from steric sea surface height phases extracted with a plane-wave fit technique. On monthly time scales, the loss of phase coherence in the equatorward beams from the French Polynesian Islands is attributed to the time variability in the sheared background flow associated with the jets and tropical instability waves. On an annual time scale, the effect of stratification variability is of equal or greater importance than the background flow is to the loss of coherence. The model simulation suggests that low-frequency jets do not noticeably enhance the dissipation of the internal tide, but merely decohere and scatter it. Thus, the apparent demise of coherent internal tides seen in satellite altimetry maps of the equatorial Pacific may be due to incoherence rather than dissipation.


Carlos Herdeiro
Departamento de Física
Universidade de Aveiro — Portugal

Can a Black Hole Have Hair?

Black holes are one of the most fascinanting predictions of Einstein's theory of General Relativity. In their most paradigmatic guise, they are also the simplest objects in the Universe, made solely of space and time. Moreover, powerful mathematical theorems, known as uniqueness theorems, show that the way space and time can curve into a black hole is quite restricted, and these objects are only described by two parameters: their total mass and angular momentum. John Wheeler famously coined this simplicity into the mantra "Black Holes have no hair". But underlying this statement there is an unproved belief known as the "no-hair conjecture".

I will start by discussing observational evidence for the existence of black holes in the universe. Then, I will explain why the existence of some simple types of matter, even if Einstein's theory holds, could challenge the no-hair conjecture and produce "hairy" black holes. Finally, I will discuss how ongoing and forthcoming electromagnetic and gravitational waves observations could test the existence of black hole "hair" of this sort.


Seth Hopper
Gravitation in Técnico
Instituto Superior Técnico — Portugal

Bound and Unbound Motion Around Static Black Holes

A massive two-body system will interact gravitationally. Depending on the velocities and separation of bodies, their motion may be bound and periodic (as in the Earth-Sun system) or unbound (like a comet that passes the Sun only once). General relativity predicts that each of these systems will radiate energy in the form of gravitational waves. However, the qualitative difference between the systems implies that different techniques must be used to analyze them. In this talk I will briefly introduce the mathematical theory behind gravitational radiation of two body systems (specifically in the extreme mass-ratio regime) and consider how one can efficiently compute that radiation for different classes of problems.


Tanaz A. Mohayai
Department of Physics
Illinois Institute of Technology

Measurements Of Beam Cooling In Muon Ionization Cooling Experiment

The international Muon Ionization Cooling Experiment, MICE, is a high energy physics experiment located at Rutherford Appleton Laboratory in the U.K., and its aim is to demonstrate muon beam cooling for the first time. When muons are produced from pion decay, they occupy a large volume in the position-momentum phase space and the process of reducing their volume is known as beam cooling. Several beam cooling techniques exist, but the ionization cooling is the only technique fast enough to be used for muons within their short lifetime. Ionization cooling occurs when the beam loses momentum through energy loss, while traversing a material. In MICE, commonly used figures of merit for cooling are the beam emittance reduction, the phase-space volume reduction, and the phase-space density increase. Emittance is the measure of the size of the beam, and with a reduced beam emittance or phase-space volume, more muons can fit in a smaller aperture of a cost-effective accelerator. This may enable the construction of a future high-intensity muon accelerators, such as a Neutrino Factory or a Muon Collider. To demonstrate beam cooling, MICE makes use of two scintillating-fiber tracking detectors, immersed in the constant magnetic fields of the Spectrometer Solenoid modules. These trackers, one upstream and one downstream of the absorber reconstruct and measure the position and momentum coordinates of individual muons, and the absorber provides the ionization energy loss required for beam cooling. The choice of absorber material is dependent on the achievable energy loss, and the aim is to maximize beam cooling through energy loss while minimizing beam heating from multiple Coulomb scattering. In addition, given the precision with which MICE aims to demonstrate beam cooling, it is necessary to develop analysis tools that can work around any effects which may lead to inaccurate cooling measurements. Non-linear effects in beam optics is one example of such effects and it can result in apparent emittance growth or beam heating. The Kernel Density Estimation, KDE technique is an analysis tool which is insensitive to these non-linear effects and measures the muon beam phase-space density and volume. This talk will give an overview of the recent MICE results, the emittance measurement technique in the recent MICE data, and the novel application of the KDE technique in MICE.