Calendar of Physics Talks Vienna

Nanomechanical Systems
Speaker:Eva Weig (LMU Munich)
Abstract:Nanomechanical resonators are freely suspended bridges with nanoscale diameters which can be realized using top-down nanofabrication. We explore the mechanical vibrations of the resulting beams and strings. However, the physical properties of these tiny oscillators differ fundamentally from macroscopic mechanical objects: The dissipation increases with shrinking dimensions, and anharmonicities provide a nonlinear mechanical response. The investigation of nanomechanical resonators calls for novel actuation schemes, and often produces astounding results, three of which will be presented today. A mechanical shuttle transports single electrons between two electrodes and supports self-sustained oscillation without resonant actuation. Dielectric beams can be driven and analyzed in gradient fields, allowing to resolve the Brownian motion with a resolution exceeding the quantum mechanical zero-point fluctuations. And coupling to an optical cavity results in back-action induced manipulation of the mechanical response, which can give rise to self-oscillation and cooling. Thus, the investigation of nanomechanical systems bears potential for a wide spectrum of applications, ranging from high-resolution sensing and signal processing to fundamental investigations approaching the limits of quantum mechanics.
Date: Mon, 10.01.2011
Time: 17:30
Duration: 60 min
Location:Univ. Wien, Ernst-Mach-Hörsaal, Boltzmanngasse 5, 2nd floor, 1090 Wien

In-medium eta' mass reduction in Au+Au collisions at RHIC
Speaker:T. Csorgo (Department of Physics, Harvard University, Cambridge, MA and MTA KFKI RMKI, Budapest, Hungary )
Abstract:In relativistic heavy ion collisions at RHIC, BNL, USA, a perfectly flowing fluid of quarks, the strongly interacting Quark Gluon Plasma was identified in February 2010. The characteristic initial temperatures Tinit exceed 300 MeV, they are significantly above the Hagedorn limit of 170 MeV above which temperature hadrons as we know them may not exist. In this talk I first summarize the milestones of the RHIC heavy ion program, then I will focus on a recent analyzes of PHENIX and STAR data on the intercept parameter of the two-pion Bose-Einstein correlation functions in sqrt(s_{NN}) = 200 GeV Au+Au collisions in terms of different models. To describe this combined PHENIX and STAR dataset, an in-medium eta' mass reduction of at least 200 MeV was needed, at the 99.9 % confidence level in the considered model class. Such a significant eta' mass modification may indicate the restoration of the U_A(1) symmetry in a hot and dense hadronic matter and the return of the 9th "prodigal" Goldstone boson. References: T. Csörgő, R. Vértesi, J. Sziklai, Phys.Rev.Lett.105:182301,2010 R. Vértesi, T. Csörgő, J. Sziklai, Nucl.Phys.A830:631c-632c,2009
Date: Tue, 11.01.2011
Time: 14:00
Duration: 60 min
Location:Institut für Hochenergiephysik, Nikolsdorfergasse 18, Bibliothek
Contact:Dietrich Liko

Euklidische Green-Funktionen und das Osterwalder-Schrader-Theorem
Speaker:Hans-Linus Pfau und Peter Poier (Univ. Wien) (Fakultät für Physik)
Abstract:im Rahmen des Seminars für Mathematische Physik
Date: Tue, 11.01.2011
Time: 14:15
Duration: 60 min
Location:Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock, 1090 Wien
Contact:J. Yngvason

Secondary Electron Yield on Cryogenic Surfaces as a function of physisorbed gases
Speaker:Dipl.-Ing. Asena Kuzucan (Cern/CH)
Abstract:In LHC the electron cloud (EC) induced by photoelectrons, gas ionization and secondary electrons emitted from the beam pipe walls could be a limitation of the performance. The EC induces heat load on the cryogenic system, causes pressure rise, emittance growth and beam instabilities, which in the end will limit the beam’s lifetime. The secondary electron yield (SEY) is one of the key parameters for the electron cloud build up and the multipacting phenomenon. It has been extensively studied on room temperature samples but uncertainties remain for samples at cryogenic temperature. Indeed, at low surface temperature SEY is strongly dependent on the nature of the physisorbed gases and on the surface coverage. In this work the SEY of different physisorbed gases (N2, Kr, CH4, CO, CO2, C2H6) on copper and aluminium samples has been measured and discussed.
Date: Tue, 11.01.2011
Time: 16:00
Location:Technische Universität Wien, Institut für Angewandte Physik, Seminarraum 134A, Turm B (gelbe Leitfarbe), 5. OG, 1040 Wien, Wiedner Hauptstraße 8-10
Contact:Ao.Univ.Prof. Dr. Herbert Störi

On the principle of symmetric criticaliy I
Speaker:Helmuth Urbantke (Wien) (Fakultät für Physik)
Abstract:im Rahmen des Literaturseminars
Date: Thu, 13.01.2011
Time: 13:30
Duration: 60 min
Location:Arbeitsgruppe: Gravitation, Währinger Strasse 17, Seminarraum A, 2. Stock
Contact:P. Chrusciel

Alpha_s determinations and DIS fits
Speaker:Johannes Blümlein (DESY Zeuthen)
Abstract:im Rahmen des Teilchenphysikseminars
Date: Thu, 13.01.2011
Time: 14:15
Duration: 60 min
Location:Fakultät für Physik, Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock, 1090 Wien
Contact:A. Hoang, H. Neufeld