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Events on Thursday, April 26th, 2012

R. G. Herb Condensed Matter Seminar
"Rare" Fluctuations and the Anderson Model of Localization
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Ravin Bhatt, Princeton University
Abstract: It has been over fifty years since Anderson's original paper reporting the discovery of the absence of diffusion in random lattices, and over three decades since the metal-insulator transition was understood in terms of the scaling theory of localization. Despite this long time interval, and thousands of publications on the subject, the Anderson model of localization continues to offer new insights. In this talk we examine the Anderson model at large disorder (i.e. in the insulating phase). We find, surprisingly, new singularities in this regime, which had apparently escaped attention. These singularities appear to demarcate the boundary between "typical" and "rare fluctuation" states. (The latter are the counterpart of rare fluctuation effects found to be quite pervasive in quantum many-body models with large disorder). Besides exposing a new facet of a seemingly simple and extensively studied model, our work suggests that Anderson's model of localization offers an unparalleled opportunity to understand rare fluctuation effects at a level of detail that has not been possible in numerical approaches to many-body models.
Host: Susan Coppersmith
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Dark Matter from Weak Polyplets
Time: 2:30 pm
Place: 4274 Chamberlin
Speaker: Jennifer Kile, Northwestern University
Abstract: We investigate the possibility of new fermion multiplets charged under the Standard Model gauge group, with the aim of obtaining a possible dark matter candidate. These new fermions are charged under SU(2)xU(1); their quantum numbers are determined by requiring anomaly cancellation and insisting that all new particles become massive via Yukawa couplings with the SM Higgs boson. Constraints from colliders, electroweak precision measurements, and DM direct detection are considered; we find that this model can accommodate a viable DM candidate.
Host: Michael Ramsey-Musolf
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