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
Graduate Students
Department of Physics and Astronomy
University of Mississippi
Temperature Dependent Behavior of Shear Waves in a Micellar Fluid (Sunethra Dayavansha)
Development of Brain Tissue-Mimicking Phantom (Somayeh Taghizadehghahremanloo)
Negative Refraction and Super-resolution by a Steel-methanol Phononic Crystal (Ukesh Koju)
Development of a Tilt-free Seismometer (Reza Afrough)
The RKKY Interaction for Link Variables on the Square Lattice (Huu Do)
Experimental Test of an Omnidirectional Acoustic Enhancement Method (Maryam Landi)
Deforming the Fredkin Spin Chain away from its Frustration-free Point (Khagen Adhikari)
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)
The Problem of Gauge Fixing in the Newman-Penrose Formalism (Andrea Nerozzi)
Dynamics of Compact Binary Systems at the Fourth Post-Newtonian Order (Laura Bernard)
Tue, Mar 14
Lewis 101
Spring Break
 
 
 
Tue, Mar 21
Lewis 101
Sabrina Savage
Science Research Office
Marshall Space Flight Center
Reconnecting with Solar Flares
Tue, Mar 28
Lewis 101
Ulrich Sperhake
Theoretical Astrophysics
California Institute of Technology
Searching for Smoking Gun Effects of Modified Gravity in Supernova Core Collapse
Tue, Apr 4
Lewis 101
Michael Allshouse
Department of Mechanical and Industrial Engineering
Northeastern University
Internal Wave Breaking and Boluses
Tue, Apr 11
Lewis 101
Wanwei Wu
Department of Physics and Astronomy
University of Mississippi
The Muon g-2 Experiment at Fermilab
(PDF 125 MB)
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
Laser Interferometer Space Antenna (LISA)
Tue, May 2
Lewis 101
Bevin Etienne
McIntire School of Commerce
University of Virginia
The Role of Microgrids and Community Choice Aggregation in Building a Sustainable and Resilient Energy System
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 mimic 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.


Andrea Nerozzi
Gravitation in Técnico
Instituto Superior Técnico — Portugal

The Problem of Gauge Fixing in the Newman-Penrose Formalism

Since its introduction the Newman-Penrose formalism has been widely used in analytical and numerical studies of Einstein's equations, like for example for the Teukolsky master equation, or as a powerful tool for wave extraction in numerical relativity. The problem of gauge fixing, or more specifically, tetrad fixing is however still debated and only partially understood when the NP formalism is used to extract gravitational waves from numerical simulations.

In this talk I will approach the whole formalism with the goal of finding an invariant expression for all the variables in the NP formalism, namely Weyl scalars and the spin coefficients, once a specific yet generally defined tetrad is chosen.I will show that it is possible to do so, and give a general recipe for the task, as well as an indication of the quantities and identities that are required. The applications and importance of this approach to the problem of wave extraction in numerical relativity will be discussed.


Laura Bernard
Gravitation in Técnico
Instituto Superior Técnico — Portugal

Dynamics of Compact Binary Systems at the Fourth Post-Newtonian Order

Templates of coalescing compact binaries' gravitational waveform are used for the detection and precise determination of the physical parameters of gravitational waves by the current and next generations of interferometric detectors. In order to compute the waveform with high accuracy, the dynamics of compact binary systems should be known to the same precision. In this talk, I will address the question of the dynamics of non-spinning compact binary systems at the fourth post-Newtonian order in harmonic coordinates. I will present a method based on a Fokker action adapted to the specificities of the post-Newtonian formalism, including the so-called tail effects which appear for the first time in the conservative dynamics at 4PN. I will then derive the energy and periastron advance for circular orbits and show a full agreement with previous results from gravitational self-force calculations.


Sabrina Savage
Science Research Office
Marshall Space Flight Center

Reconnecting with Solar Flares

Because the Earth resides in the atmosphere of our nearest stellar neighbor, events occurring on the Sun's surface directly affect us by interfering with satellite operations and communications, astronaut safety, and in extreme circumstances, power grid stability. Solar flares, the most energetic events in our solar system, are a substantial source of hazardous space weather affecting our increasingly technology-dependent society. While flares have been observed using ground-based telescopes for over 150 years, modern space-bourne observatories have provided nearly continuous multi-wavelength flare coverage that cannot be obtained from the ground. We can now probe the origins and evolution of flares by tracking particle acceleration, changes in ionized plasma, and the reorganization of magnetic fields. I will walk through our current understanding of why flares occur, show several examples of these fantastic explosions, and describe the technology and instrumentation being developed at Marshall Space Flight Center to observe these phenomena.


Ulrich Sperhake
Theoretical Astrophysics
California Institute of Technology

Searching for Smoking Gun Effects of Modified Gravity in Supernova Core Collapse

Even though Einstein's theory of general relativity has been an incredibly successful theory and passed a plethora of tests ranging from light bending to the recent detection of gravitational waves, there are indications from theory, astrophysics and cosmology that modifications to the theory may ultimately be required. One of the most popular modifications applied to general relativity is the addition of a scalar field as an extra channel to mediate gravity. Through the introduction of additional degrees of freedom such scalar-tensor theories may explain some of the potentially troublesome phenomena in gravity while preserving compatibility with solar system and other tests. In this talk we explore the dynamics and gravitational wave emission of supernova core collapse in scalar tensor theory for the case of spherical symmetry. We analyse the resulting waveforms and explore under which conditions they may provide smoking gun signals detectable with present and future gravitational-wave detectors.


Michael Allshouse
Department of Mechanical and Industrial Engineering
Northeastern University

Internal Wave Breaking and Boluses

The shoaling of internal waves on a continental slope results in wave steepening and breaking that produces boluses, which are trapped regions of fluid that travel up the slope with the wave. Unlike a propagating solitary wave, these boluses transport material with the wave containing oxygen depleted water and induce rapid changes in temperature both of which have potential ramifications for marine biology. The dramatic difference between the fluid inside the bolus relative to the exterior may also impact local acoustic measurements of the sea floor. We extend a number of two-layer studies by investigating bolus generation and material transport in continuously stratified fluids. Laboratory experiments are conducted in a 4 m long tank and are complemented by 2-dimensional numerical simulations. The boundaries of the bolus are identified using a Lagrangian based coherent structure method relying on trajectory clustering. We use the structure identification to measure the properties of the bolus as a function of the pycnocline thickness and slope angle.


Wanwei Wu
Department of Physics and Astronomy
University of Mississippi

The Muon g-2 Experiment at Fermilab

The muon anomalous magnetic moment (g-2) has played an important role in constraining physics beyond the Standard Model for many years. The Fermilab Muon g-2 Experiment has a goal to measure it to unprecedented precision: 0.14 ppm, which will have a fourfold improvement compared to the BNL g-2 Experiment (0.54 ppm) as well as provide one of the most sensitive tests of the completeness of the Standard Model by comparing with the theory. The Fermilab g-2 Experiment is close to the end of installation and ready for the commissioning and physical running soon. In this talk, I will give an overview of the experiment and discuss the work involved by the OleMiss group.


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.


Guido Mueller
Department of Physics
University of Florida

Laser Interferometer Space Antenna (LISA)

The last 18 months did not only see the first direct detection of gravitational waves by LIGO but also the successful launch and operation of the LISA Pathfinder (LPF) mission. While the LIGO detection sparked the scientific but also the public interest in these 'mysterious' waves, the LPF results show that a space-based gravitational wave observatory is within reach.

Even prior to that, ESA selected the gravitational universe as the science theme for their L3 mission and asked an advisory team to evaluate the technical maturity of all available mission concepts and technologies for a launch of a space-based gravitational wave mission in 2034. This advisory team concluded that a space-based gravitational wave observatory should be based on laser interferometry and gravitational reference sensor technology as tested by LPF. Following the 'magic spring' of 2016, ESA released a call for mission proposals and selected the one submitted by the LISA consortium for further studies. LISA's goal is to detect the infrasound of the universe and detect gravitational waves over five decades in frequency centered around a few mHz. Expected sources range from hundred thousand compact galactic binaries to extreme mass ratio inspirals out to redshifts up to 2 to massive and supermassive black hole mergers in the million to hundred million solar mass mass ranges out to redshifts of 20. LIGO sources years before the merger have recently been added to LISA's source catalogue. Guido Mueller will discuss the technology used in LISA, its readiness, and also the status of LISA as a project within ESA and NASA.


Bevin Etienne
McIntire School of Commerce
University of Virginia

The Role of Microgrids and Community Choice Aggregation in Building a Sustainable and Resilient Energy System

Energy plays a role in every facet of our lives - from food production to clothing and shelter, to the water we drink and the air we breathe and by great extent our ability to do the work we enjoy. With that being said, the energy sector, globally, is plagued with many challenges. For example, the electric grid and most of the energy infrastructure in the US was constructed in the 1950s and 1960s with a 50-year life expectancy1 which signifies the US is due for an overhauling of the system. This does not account for the fact that the energy system of the 1950s and 1960s was not engineered to meet today's energy demands and capability to withstand severe weather related events – in 2012, Super storm Sandy demonstrated our energy system vulnerability to severe weather. All of this suggests that the time is at hand for significant investment in maintaining, upgrading and rebuilding the electric energy infrastructure. Recently conducted research suggests that the replacement value of the U.S. electric grid is $4.8 trillion2.

This discussion will focus on the use of Microgrids and Community Choice Aggregation (CCA) in addressing the impending energy crisis and assess the social, economic and environmental benefits of employing such an approach to tackling the current energy challenge. Beyond the US, microgrids and CCA offer the opportunity for developing nations to leapfrog the centralized energy infrastructure and provide a more sustainable and secure energy system for the 21st century.


1The American Society of Civil Engineers (ASCE) 2017 Infrastructure Report Card
2Tsvetana Paraskova, OilPrice.com