Probing the Accelerating Universe with the Dark Energy Survey UF Physics Colloquium Physics Home

PHYSICS COLLOQUIUM SCHEDULE
Fall 2017

The Colloquia are in Room 1002 NPB on Thursday at 4:05 PM
Refreshments will be served starting at 3:15 PM in NPB 2205

Contact: A. Hebard afh@phys.ufl.edu)
Department of Physics Colloquium Committee:
Hebard (Chair), Fry, Furic, Mitselmakher, Obukhov, Ramond (members)


AUGUST 24

  Speaker Graduate Student Meeting with Dr. Xiaoguang Zhang 4:00pm in 1002 NPB

August 31

  Speaker Amlan Biswas, UF Physics
  Title Magnetoelectrism in crystals
  Abstract A discussion of the magnetic properties of matter usually addresses the effect of magnetic fields on magnetization. While the effect of an electric field on magnetism is also firmly established, we are much more familiar with the equation M = χmH than with M=αE, where χm is the magnetic susceptibility and α quantifies the magnetoelectric effect. A reason for this unfamiliarity is that α is negligible for most magnetic materials. I will discuss the origin of the magnetoelectric effect in materials and why the effect is small in single phase materials. I will describe our experiments on three materials from the perovskite family: LaPrCaMnO3, BiMnO3, and SrTiO3 and the unexpectedly large magnetoelectric coupling we observed under certain conditions. Ongoing experiments in our research group have been designed to fabricate and study these materials and further enhance their magnetoelectric properties.
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SEPTEMBER 7

  Speaker James Hamlin, UF Physics
  Title The expanding role of compressed matter in superconductivity research
  Abstract Measurements at low temperature are a standard part of the characterization of newly discovered materials. Due to their technical difficulty, measurements under high pressure conditions are not nearly as ubiquitous. Consequently, the vast majority of materials have yet to be characterized under pressure. The recent discoveries of high-temperature superconductivity in compressed iron selenide and hydrogen sulfide hint that many exciting discoveries still await in the unexplored high-pressure phases of otherwise well-studied materials. In this talk, I will provide an overview of results obtained using a new apparatus that combines designer diamond anvils with automated pressure measurement and application in order to to rapidly locate and characterize pressure induced phase transitions. Using elemental barium metal as an example, I will also present work using this apparatus to examine superconductivity in metastable structures obtainable only by varying pressure under cryogenic conditions. Finally, I will discuss an ongoing collaborative effort which combines synthesis, high pressure measurements, and high-throughput computation with the aim of accelerating the discovery of pressure-induced superconductors.
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SEPTEMBER 14

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SEPTEMBER 21

  Speaker Tim Sumner (Imperial College)
  Title Celestial Dynamics: The Mystery Deepens
  Abstract The mid-1980s saw the birth of many dedicated direct dark matter search experiments, starting up as a result of the mounting evidence for enhanced gravitational potentials in a number of astrophysical systems, and in the light of many particle-physics frameworks predicting new (suitable) particles. These experiments and indeed many other indirect search experiments have made solid progress since then but still we lack any definitive evidence. Meanwhile there has been interesting growth in alternative gravity scenarios, but also leaving us without a clear solution. This talk will review the situation and look forward to what the future might hold with new experiments and new types of observation.
Host Mueller

SEPTEMBER 28

  Speaker Klaus Honscheid, The Ohio State University
  Title Probing the Accelerating Universe with the Dark Energy Survey
  Abstract Why is the expansion of the universe speeding up? Is cosmic acceleration due to dark energy or does it require a modification of General Relativity? If itís due to dark energy, is it the energy density of the vacuum (Einstein's cosmological constant) or something else? To address these questions, the Dark Energy Survey (DES) collaboration built the 570-megapixel Dark Energy Camera for the Blanco 4-meter telescope at NOAO's Cerro Tololo Inter-American Observatory in Chile, to carry out a 5-year, deep, multi-band, optical survey of several hundred million galaxies and several thousand supernovae. The DES survey began in 2013 and recently started the fifth and final observing season. In this talk I will highlight recent results and discuss how DES is measuring the history of cosmic expansion and the growth of structure using complementary techniques including the large-scale galaxy distribution and weak gravitational lensing of the light emitted by 26 million distant galaxies.
Host Darin Acosta

OCTOBER 5

  Speaker Vivien Zapf, NHMFL
Title New path to multiferroic behavior
  Abstract Multiferroics are materials where magnetism and ferroelectricity coexist and possibly couple to each other. Research is driven by the intriguing interplay of spin, charge and lattice, as well as potential applications since they lower power consumption compared to spintronics by several orders of magnitude. To date, multiferroic research has focused on inorganic materials such as oxides. However a growing research effort is devoted to classes of materials that combine magnetic ions with organic ligands, such as metal-organic frameworks and molecular magnets. These materials offer different mechanisms for both magnetism and ferroelectricity and can have significant coupling between them due to the soft lattices. In particular, I will present a new result on creating multiferroic behavior using a spin state transition. Whereas in conventional magnetic order, the spin directions spontaneously form patterns, in spin state transitions, the total spin of the 3d magnetic ion changes due to a change in the occupation of partially-filled d orbitals. Spin state transitions can be strongly-coupled 1st order phase transitions driven by temperature, magnetic field, pressure, or other tuning parameters. Spin-state transitions can occur up to room temperature at ambient pressures in 3d transition metal-organic systems. Here, we demonstrate that these spin state transitions can lead to multiferroic behavior in a molecular magnetic materials.
Host Art Hebard

OCTOBER 12

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OCTOBER 19

  Speaker Postponed to October 26
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OCTOBER 26

  Speaker Chris Lobb (University of Maryland)
  Title Ohmís Law and Beyond for Atom Circuits
  Abstract Atomtronics is an emerging interdisciplinary field that is creating new devices and circuits where ultracold atoms, often in the superfluid state, have a role analogous to that of electrons in electronics. After giving a brief overview of some experimental neutral atom-circuit results, I will show how these results can be described by lumped-element models analogous to those used in electronics. Resistance, capacitance and inductance can be defined for neutral-atom circuits, and they are analogous to the Sharvin resistance (in the non-superfluid case), quantum capacitance, and kinetic inductance, respectively, in electronic circuits. In the superfluid case, quantum coherence leads to behavior analogous to superconducting quantum interference devices (SQUIDs) and vortex-induced resistance. In collaboration with R. B. Blakestad, G. K. Campbell, C. W. Clark, S. Eckel, M. Edwards, K. Helmerson, W. T. Hill, III, F. Jendrzejewski, J. G. Lee, B. J. McIlvain, S. R. Muniz, N. Murray, W. D. Phillips, A. Ramanathan, K. C. Wright, and M. Zelan.
Host Art Hebard


NOVEMBER 2

  Speaker Corene Matyas, UF Department of Geography
Title Hurricanes: from formation to landfall
  Abstract Tropical cyclones require specific dynamic and thermodynamic conditions to form, and those conditions have been present over much of the Atlantic Basin during the 2017 hurricane season. This presentation begins by discussing these conditions and illustrates them using examples from Hurricanes Harvey and Irma as they were discussed during the hurricanes course that I teach during fall semesters. In the second part of the presentation, I present an overview of my research that examines the spatial distribution of rainfall regions as tropical cyclones approach and move over the United States. The first study examines climatological rainfall and wind patterns for landfalls occurring during 1948-2014. The second study measures the radial and azimuthal distribution of rainfall according to radar data and illustrates how the evolution of rainfall after landfall corresponds to interaction with the relatively dry continental air mass, de-intensification, and proximity to frontal boundaries. This research is sponsored by a CAREER Award from the National Science Foundation.
Host Pierre Ramond

NOVEMBER 9

  Speaker Shane Larson, CIERA, Northwestern University
Title Probing the Stellar Graveyard: Gravitational waves from ultra-compact binaries
  Abstract The population of ultra-compact binaries in the Milky Way encodes a fossil record of stellar evolution in the galaxy. Taken as a population, the distributions of stellar types, orbital parameters, and masses encodes the signatures of processes that drive the evolution of these systems, including common envelope phases and epochs of mass transfer. LISA is a planned gravitational wave interferometer in space, a million times larger than their ground-based counterparts. The enormous size makes LISA sensitive to orbital periods in the range of hundreds to tens of thousands of seconds, a regime populated by binary systems comprised of white dwarfs, neutron stars, and black holes. All told, there should be some 10 million such systems in the Milky Way, providing an ample discovery space to map out and characterize these sources. In this talk we'll discuss LISA observations of the ultra-compact binary population. We'll discuss current work that illustrates how to use population synthesis to model the galaxy, and examine recent work that shows how joint gravitational wave and electromagnetic observations can constrain mass transfer processes in these systems.
Host Guido Mueller

SPECIAL COLLOQUIUM - FRIDAY, NOVEMBER 17

  Speaker Dan Green, Fermilab
  Title Fermilab and the Foundations of the Standard Model
  Abstract Fermilab has been a leader in the exploration of the Standard Model throughout its 50 year history. The past history will be reviewed. The present, with international collaboration between the U.S. and CERN, exploration beyond the SM (BSM) is the future with FNAL and DUNE and CERN and the high luminosity LHC (HL LHC).
Host Darin Acosta.

NOVEMBER 30

  Speaker Robert Brandenberger, McGill University
  Title Testing String Theory with Cosmological Observations
  Abstract Current paradigms of early universe cosmology suffer from a number of conceptual problems. I will explore the possibility that superstring theory could lead to a new scenario of the very early universe, and that this scenario could be tested with cosmological observations."
Host Richard Woodard



PHYSICS COLLOQUIUM SCHEDULE

Spring 2018

The Colloquia are in Room 1002 NPB on Thursday at 4:05 PM
Refreshments will be served starting at 3:15 PM in NPB 2205

Contact: A. Hebard afh@phys.ufl.edu)
Department of Physics Colloquium Committee:
Hebard (Chair), Fry, Furic, Mitselmakher, Obukhov, Ramond (members)


JANUARY 11

  Speaker Steve Kivelson (Stanford University)
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  Host Peter Hirschfeld

JANUARY 18

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JANUARY 25

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FEBRUARY 1

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FEBRUARY 8

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FEBRUARY 15

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FEBRUARY 22

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MARCH 1

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MARCH 8

  Speaker APS meeting and spring break
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MARCH 15

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March 22

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March 29

  Speaker Barry Barish, Caltech
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  Host Guenakh Mitselmakher

April 5

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APRIL 12

  Speaker Nadya Mason (UIUC)
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  Host Amlan Biswas

APRIL 19

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