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Events During the Week of January 17th through January 24th, 2016

Monday, January 18th, 2016

No events scheduled

Tuesday, January 19th, 2016

Chaos & Complex Systems Seminar
The Universe: Yesterday, today, and tomorrow
Time: 12:05 pm - 1:00 pm
Place: 4274 Chamberlin Hall
Speaker: Ed Churchwell, UW Department of Astronomy
Abstract: Based on the current Standard Model, we will take an excursion in time to examine the properties of the Universe from just after the Big Bang to the present and into the future. This will begin with a discussion of the primary observations that underpin the Standard Model and the basic physical principles that connect the observations to the current model. We will end with the current best values for the Standard Model and their implications for the future evolution of the universe.<br>
Host: Sprott
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Theory Seminar (High Energy/Cosmology)
Discrete Abelian symmetries in the MSSM and its extensions
Time: 3:30 pm
Place: 5280 Chamberlin Hall
Speaker: Volodymyr Takhistov, University of California, Irvine
Abstract: Discrete symmetries play a major role in particle physics. With supersymmetry being one of the most well motivated extensions of the Standard Model, discrete symmetries have been employed in the context of minimal supersymmetric Standard Model (MSSM) to resolve various issues such as fast proton decay and the mu-problem. We systematically explore anomaly free and phenomenologically viable discrete Abelian (R-)symmetries for the MSSM, considering both R-parity conserving as well as violating (RPV) scenarios. Among the new solutions that we obtain, some RPV models are found to be compatible with the Pati-Salam unification and some favor Dirac neutrino mass. Additionally, we present a novel general algorithm for identifying a maximal discrete symmetry for a given particle content and a set of constraints.
We describe how such discrete symmetries may be used as a basis for construction of more complete models, which also address baryogenesis and flavor sector. Since proton decay is one of the most severe constraints for such models, we will briefly mention some of the novel proton decay searches at the Super-Kamiokande experiment. Finally, we will also show how the lack of stabilizing discrete Z3 symmetry in the context of lepton-flavored dark matter (DM) models can lead to interesting DM decay channels.
Host: Yang Bai
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Wednesday, January 20th, 2016

Department Meeting
Time: 12:15 pm
Place: 5310 Chamberlin Hall
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Thursday, January 21st, 2016

R. G. Herb Condensed Matter Seminar
Transport coefficients of graphene: Interplay of impurity scattering, Coulomb interaction, and optical phonons
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Hong-Yi Xie, Department of Physics and Astronomy, Rice University
Abstract: We study the electric and thermal transport of the Dirac carriers in monolayer graphene using the Boltzmann-equation approach. Motivated by a recent thermopower measurement [F. Ghahari, H.-Y. Xie, M.S. Foster, and P. Kim, in preparation], we consider the effects of quenched disorder, Coulomb interactions, and electron--optical-phonon scattering. Via an unbiased numerical solution to the Boltzmann equation we calculate the electrical conductivity, thermopower, and electronic component of the thermal conductivity, and discuss the validity of Mott's formula and of the Wiedemann-Franz law. An analytical solution for the disorder-only case shows that screened Coulomb impurity scattering, although elastic, violates the Wiedemann-Franz law even at low temperature. For the combination of carrier-carrier Coulomb and short-ranged impurity scattering, we observe the crossover from the interaction-limited (hydrodynamic) regime to the disorder-limited (Fermi-liquid) regime. In the former, the thermopower and the thermal conductivity follow the results anticipated by the relativistic hydrodynamic theory. On the other hand, we find that optical phonons become nonnegligible at relatively low temperatures and that the induced electron thermopower violates Mott's formula. Combining all of these scattering mechanisms, we obtain the thermopower that quantitatively coincides with the experimental data.
Host: Alex Levchenko
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Friday, January 22nd, 2016

No events scheduled