Calendar of Physics Talks Vienna

The absolute boundary of the random walks on the groups and graphs
Speaker:Prof. Anatoly Vershik (Steklov Institute and State University St. Petersburg)
Abstract:We will define the notion of absolute boundary (Dynkin exit boundary) and describe this notion for several classes of groups and graphs. The case of free group was studied with A. Malutin.
Date: Tue, 23.02.2016
Time: 13:00
Duration: 60 min
Location:Erwin Schrödinger International Institute, Boltzmanngasse 9, 1090 Wien, Boltzmann lecture hall

Computability of Følner sets and sofic approximations
Speaker:Dr. Matteo Cavaleri (U Rome/U Vienna)
Abstract:In the class of finitely generated groups we recall equivalent definitions for sofic groups, amenable groups, word problem and a quantification of soficity, the sofic dimension growth. We present the Minsky machines in order to define computability and to give an idea of the construction of the Kharlampovich group, a finitely presented solvable group with unsolvable word problem. We prove the computability of Følner sets and the non computability of sofic approximations for Kharlampovich group. More generally we study the classes of groups with computable Følner sets, with subrecursive sofic dimension growth and their stability properties.
Date: Wed, 24.02.2016
Time: 15:00
Location:Erwin Schrödinger International Institute, Boltzmanngasse 9, 1090 Wien, Boltzmann lecture hall

Hot carrier effects in spin-diffusion studies of semiconductors
Speaker:Tobias Kießling (Universität Würzburg)
Abstract:Pump-probe magneto-optical Kerr effect (MOKE) microscopy is a heavily used tool for the investigation of electron spin transport in semiconductors. However, while the significance of pump-induced electron heating for the diffusion of photoexcited carriers has long been understood in the related context of excitonic transport, hot electron effects have mostly been neglected in the interpretation of results on electron spin diffusion obtained by MOKE microscopy. We show that in case of the widely applied optical detection by means of continuous wave magneto-optical Kerr spectroscopy one has to carefully take into account the impact of hot carrier effects on the magneto-optical response function, which then is spatially non-uniform.
Date: Wed, 24.02.2016
Time: 16:00
Duration: 45 min
Location:Seminarraum DC rot 07 (roter Bereich, 7. OG), Wiedner Hauptstraße 8-10, 1040 Wien
Contact:Andrei Pimenov

Charmed-strange meson spectrum: past, present and future challenges
Speaker:Dr. Elisabetta Prencipe (Forschungszentrum Juelich)
Abstract:Recent observations at the LHCb experiment strongly motivate the increasing attention in charm spectroscopy, from theoretical and experimental points of view. Several questions remain opened on the correct interpretation of the charm spectrum. Different theoretical models exist, leading to different interpretations; higher precision is then demanded to the experiments to discriminate among them. An overview of the interesting measurements in charm spectroscopy performed by the past B factories and the present running CERN experiments is given, showing what has been understood up to now and which are the limitations. The future PANDA experiment at FAIR aims to conduct an antiproton-­proton experiment with a very high rate capability, up to 2x10^7 interaction/s. It is expected to feature high mass resolution... [for full abstract please visit: https://indico.smi.oeaw.ac.at/event/134/]
Date: Wed, 24.02.2016
Time: 17:00
Duration: 60 min
Location:Stefan-Meyer-Institut, Boltzmanngasse 3, 1090 Wien, Seminarraum 3-2-08 (2. Stock)
Contact:Prof. Dr. Eberhard Widmann, Dr. Martin Simon