Department of Physics and Astronomy

University of Mississippi

Events

  • Tue
    28
    Mar
    2017
    4:00 pmLewis 101

    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.

  • Sun
    02
    Apr
    2017
    8:15 pmKennon Observatory

    We are offering astronomy open houses and viewings with our telescopes:

    • April 2, Sunday, 8:15 - 10:30 PM

    We plan to observe  the Moon,  nebulae  and  star  clusters though our telescopes.  All these events are weather permitting. Admission is free.
    Children are welcome!
    Due to the buses we have moved from Friday to Sunday nights.
    See this page for the full schedule.

  • Tue
    04
    Apr
    2017
    4:00 pmLewis 101

    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.

  • Tue
    11
    Apr
    2017
    4:00 pmLewis 101

    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.

  • Tue
    11
    Apr
    2017
    6:00 pmLuca Bakery and Cafe, 1120-1122 North Lamar Blvd Oxford, Mississippi

    Dr. Susana Martinez-Conde,
    Laboratory of Integrative Neuroscience,
    State University of New York — Downstate Medical Center

    Vision is All About Change

    Your eyes are the sharks of the human body: they never stop moving. In the past minute alone, your eyes made as many as 240 quick movements called “saccades” (French for “jolts”). A portion of our eye movements we do consciously, and are at least aware of on some level. But most of these tiny back-and-forths and ups-and-downs are unconscious and nearly imperceptible; someone staring directly at your eyes would miss most of them. Scientists long believed that we use two types of oculomotor behavior to sample the visual world, alternating between big saccades to scan our surroundings and tiny ones to fix our gaze on a location of interest. Explore, fixate, repeat, all day, every day. It seemed to make intuitive sense that we would have one brain system for exploring the environment and another for focusing on specific objects. But it turns out that exploration and gaze-fixation are not all that different processes in the brain. Instead, our eyes scan visual scenes with a same general strategy, whether the images are huge or tiny, or even when we try to fix our gaze. This insight may offer clues to understanding normal oculomotor function in the healthy brain, and oculomotor dysfunction in neurological disease.

    See this page for details.

  • Tue
    18
    Apr
    2017
    4:00 pmLewis 101

    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.

  • Tue
    25
    Apr
    2017
    4:00 pmLewis 101

    Guido Mueller
    Department of Physics
    University of Florida

    TBA

  • Tue
    02
    May
    2017
    4:00 pmLewis Hall

    Bevin Etienne
    McIntire School of Commerce
    University of Virginia

    TBA