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Events on Thursday, November 21st, 2013

R. G. Herb Condensed Matter Seminar
Probing the chiral anomaly with nonlocal transport in Weyl semimetals
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Dmytro Pesin, University of Utah
Abstract: Weyl semimetals are three-dimensional crystalline systems where pairs of bands touch at points in momentum
space, termed Weyl nodes, that are characterized by a deinotnite topological charge: the chirality. Consequently,
they exhibit the Adler-Bell-Jackiw anomaly, which in this condensed matter realization implies that application of parallel electric (E) and magnetic (B) inotelds pumps electrons between nodes of opposite chirality at a rate proportional to E*B. We argue that this pumping is measurable via nonlocal transport experiments, in the limit of weak internode scattering. Speciinotcally, we show that as a consequence of the anomaly, applying a local magnetic inoteld parallel to an injected current induces a valley imbalance that diffuses over long distances. A probe magnetic inoteld can then convert this imbalance into a measurable voltage drop far from source and drain. Such nonlocal transport vanishes when the injected current and magnetic inoteld are orthogonal, and therefore serves as a test of the chiral anomaly. Since the nodes are analogous to valley degrees of freedom in semiconductors, this suggests that valley currents in Weyl semimetals can be controlled using electric inotelds, which has potential practical aEuro~valleytronicaEuroTM applications.
Host: Perkins
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
First Evidence of High-Energy Extraterrestrial Neutrinos at IceCube
Time: 2:30 pm
Place: 5280 Chamberlin Hall
Speaker: Claudio Kooper, UW - Madison
Abstract: The spectrum of cosmic rays includes the most energetic particles ever observed. The mechanism of their acceleration and their sources are, however, still mostly unknown. Observing astrophysical neutrinos can help solve this problem. Because neutrinos are produced in hadronic interactions and are neither absorbed nor deflected, they will point directly back to their source. This talk will cover searches for high-energy neutrinos (> 100 TeV) at the IceCube neutrino observatory, which have recently produced the first evidence for a flux beyond standard expectations from neutrinos generated in the Earth's atmosphere. This includes the detection of two events with energies above 1 PeV -- the highest energy neutrinos ever observed. The current status of these astrophysical neutrino searches and prospects for the future will be discussed.

Host: Karle
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Astronomy Colloquium
Constraining the Physics of Star Formation in Galaxies Using the JVLA and GBT
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Amanda Kepley, NRAO
Abstract: Understanding how galaxies evolve requires understanding the properties of the young massive stars that mediate their structure and evolution and understanding the conditions under which these stars form. The latest generation of radio and
submillimeter telescopes are revolutionizing our ability to probe both the young massive stars and the dense molecular gas out of which they form. In this talk, I will present observations from the JVLA and GBT that demonstrate the capabilities of these telescopes and how they can tell us about the properties
of the dense gas ionized by the young massive stars in the center of a galaxy much like our own and the properties of the dense molecular gas in a starburst environment.
Host: Professor Eric Wilcots
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Outreach and Education
Chasing the Ghost Particle Premiere
Time: 7:30 pm
Place: Milwaukee Public Museum
Speaker: Prof Francis Halzen
Abstract: You are invited to the November 21 premiere of the planetarium show Chasing the Ghost Particle: From the South Pole to the Edge of the Universe, a 30-minute film about the construction and science of the IceCube Neutrino Observatory. The premiere and first run of the movie will be held at the Milwaukee Public Museum.

Professor Francis Halzen, IceCube principal investigator, will give a short introduction starting at 7:30 pm. The show will take you from the outer reaches of the universe to inside the IceCube detector, some 2,400 meters under the Antarctic ice.

Admission to the premiere is free, but seats are limited. Reserve yours today by contacting the box office at or 414-278-6951.
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