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Physics Colloquium

 

Fall 2015 Colloquium Schedule

Date Speaker Title Host
August 24 Steve Abel
UTK Chemical and Biomolecular Engineering
Contact-Mediated Spatial Organization of Membranes

Tony Mezzacappa
August 31 Seunghun Lee
University of Virginia
Spin Jam Induced by Quantum Fluctuations in a Frustrated Magnet Haidong Zhou
September 7 Labor Day Holiday: No Colloquium NA NA
September 14 Timothy Gay
University of Nebraska, Lincoln
Football: Its Physics and Future Geoff Greene
September 21 Richard Wigmans
Texas Tech
  Yuri Kamyshkov
September 28 Jané Kondev
Brandeis University
  Jaan Mannik
October 5 André de Gouvêa
Northwestern
  Yuri Kamyshkov
October 12 Eric Braaten
Ohio State University
  Lucas Platter
October 19 Raph Hix
ORNL/UT
  Tony Mezzacappa
October 26 Naoko Kurahashi Neilson
Drexel University
Detecting Cosmic Neutrinos with IceCube at the Earth's South Pole Nadia Fomin
November 2 Hiroyoshi Sakurai
RIKEN
  Robert Grzywacz
November 9      
November 16 Harald Grießhammer
George Washington University
  Lucas Platter
November 23 Chen-Yu Liu
Indiana University
  Yuri Kamyshkov
November 30 Peter Abbamonte
University of Illinois
  Adolfo Eguiluz

Abstracts

August 24, 2015

Contact-Mediated Spatial Organization of Membranes
Steve Abel, UTK Chemical and Biomolecular Engineering

Intercellular communication is often facilitated by direct physical contact between cells, with receptor-ligand recognition at the cell-cell interface triggering cell signaling and response. Such communication involves a complex interplay between molecular binding, membrane organization and mechanics, and cytoskeletal interactions. In this talk, we use theoretical and computational methods to explore problems in which receptor binding and the actin cytoskeleton influence membrane organization and shape. We first study the binding and subsequent spatial reorganization of complementary molecules on apposed membranes. When two or more molecular complexes with different natural lengths are present, the species segregate into distinct spatial regions, even in the limit of vanishing membrane surface tension and bending rigidity. We then study actin in confined membrane environments such as vesicles and membrane nanotubes. Bundles of actin filaments can significantly deform the surrounding membrane and may stabilize membrane nanotubes by suppressing membrane shape fluctuations. Our approach to these problems is linked by a theoretical framework rooted in statistical mechanics and is part of our larger research program exploring the spatiotemporal dynamics of membrane-proximal events in cells.


August 31, 2015

Spin Jam Induced by Quantum Fluctuations in a Frustrated Magnet
Seunghun Lee, University of Virginia

Can a glassy state exist in the absence of defects? This long-standing problem in condensed matter physics will be addressed in this talk by discussing glassy states found in frustrated magnets. Recently, we found that although classically the ground state of a strongly frustrated magnet is a spin liquid, quantum corrections can break the classical degeneracy into a set of aperiodic spin configurations forming local minima in a rugged energy landscape. A consequence of the complex energy landscape is that, upon cooling, the system gets trapped in one of the local minima, leading to a glassy state that we call a spin jam.[1] I will present our recent experimental work on SrCr_{9p}Ga_{12-9p}O_{19} (SCGO(p)) that revealed existence of a unique spin jam state in the vicinity of the clean limit, which strongly support the possible existence of purely topological glassy states.[2]

References
[1] I. Klich, S.-H. Lee, K. Iida, Nature Comm. 5, 3497 (2014).
[2] J. Yang et al., PNAS, In Press (2015).


September 14 , 2015

Football: Its Physics and Future
Timothy J. Gay, University of Nebraska

The game of American Football is under assault. There are several reasons for this: the media have recently discovered that football is a violent game, there are a diminishing number of jobs available for the graduates of our law schools, and our scientific understanding of concussions has improved from complete ignorance to a vague resemblance of comprehension. This talk will discuss the physics and physiology of football-related concussions and their mitigation, the history of anti-football campaigns of the past, and the future of the game itself in light of the many sociological and scientific forces aligned to end it.


October 26, 2015

Detecting Cosmic Neutrinos with IceCube at the Earth's South Pole
Naoko Kurahashi Neilson, Drexel University

The universe has been studied using light since the dawn of astronomy, when starlight captured the human eye. The IceCube Neutrino Observatory observes the universe in a different and unique way: in high-energy neutrinos. IceCube's recently discovery of a diffuse flux of astrophysical neutrinos, in other words, neutrinos from beyond the solar system, started a new era of neutrino astronomy. I will motivate why neutrinos are a necessary messenger in high-energy astronomy. I will discuss the multiple diffuse flux analyses in IceCube that observe the astrophysical flux, and what each can tell us. Spatial analyses that aim to identify the sources of such astrophysical neutrinos will also be discussed, followed by an attempt to reconcile all results, to draw a coherent picture that is the state of neutrino astronomy.


Previous Physics Department Colloquia



 

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