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Calendar of Physics Talks Vienna
| 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.
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| Date: | Mon, 10.01.2011 |
| Time: | 17:30 |
| Duration: | 60 min |
| Location: | Univ. Wien, Ernst-Mach-Hörsaal, Boltzmanngasse 5, 2nd floor, 1090 Wien |
| Contact: | christiane.losert@univie.ac.at; |
| 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
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| 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 |
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