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Events on Thursday, October 25th, 2012

R. G. Herb Condensed Matter Seminar
Majorana fermions in vortex lattices
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Rudro Rana Biswas, University of Illinois at Urbana-Champaign
Abstract: We consider Majorana fermions tunneling between vortices, within an array of such vortices in a 2D chiral p-wave superconductor. We calculate that the tunneling amplitude for Majorana fermions in a pair of vortices is proportional to the sine of half the difference between the global order parameter phases at the two vortices. Using this result we study tight-binding models of Majorana fermions in vortices arranged in a triangular or square lattice. In both cases we find that this phase-tunneling relationship leads to the creation of superlattices where the Majorana fermions form macroscopically degenerate 'flat' bands at zero energy, in addition to other dispersive bands. This finding suggests that in vortex arrays tunneling processes do not change the energies of a finite fraction of Majorana fermions and hence brighten the prospects of topological quantum computing with a large number of Majorana states.
Host: Perkins
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Astronomy Colloquium
The Magellanic Stream: Probing the Baryon Cycle in the Galactic Halo
Time: 3:25 pm - 5:00 pm
Place: 4421 Sterling Hall
Speaker: Andrew Fox, STSci
Abstract: The inflow of gas onto galaxies is a key driver of their formation and evolution.A prime local example of a gas flow is the Magellanic Stream (MS), a massive tail of material stripped out of the Magellanic Clouds and extending for almost 200 degrees across the Southern sky. The MS appears to be fragmenting and evaporating as it interacts with the hot Galactic corona, and it remains unclear how much of its neutral gas will survive to reach the Galactic disk to fuel future star formation.
I will present recent results from an ongoing observing campaign
on the MS, using UV (HST/COS) and optical (VLT/UVES) spectroscopy,
paying particular attention to the chemical and physical conditions in the gas.
Host: Bart Wakker
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Graduate Introductory Seminar
Atomic, Molecular, and Optical Physics
Time: 5:45 pm
Place: 2223 Chamberlin Hall
Speaker: Lawler, Lin, Saffman, Walker, Wehlitz, Yavuz, UW Madison
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