Calendar of Physics Talks Vienna

Schrödinger's cat in a warm bath
Speaker:Gershon Kurizki (Weizmann Institute, Rehovot, Israel)
Abstract:I will review our recent findings that defy the common notion that entanglement in multipartite systems does not survive in thermal environments. On the contrary, we find that both harmonic oscillators and multispin (multiatom) systems may become entangled via the bath to which they couple. This prompts the basic question: is quantumness, manifest by entanglement, much more ubiquitous in nature than one might suspect? The most distinct form of such bath-induced entanglement is that of Schroedinger- cat states (or macroscopic quantum- superposition states), which are synonimous with GHZ states in multispin systems. Other entangled states obtain whenever the coupling to the bath varies from one spin (or oscillator) to another. Dynamic control aimed at preserving these naturally-formed states will also be discussed. Experimental realizations will be focused on.
Date: Mon, 11.10.2010
Time: 17:30
Duration: 60 min
Location:Universität Wien, Ernst-Mach-Hörsaal, Boltzmanngasse 5, 2nd floor, 1090 Wien
Contact:Christiane Losert-Valiente Kroon

Dynamics of the Local Group in different theories of gravity
Speaker:Christoph Saulder (Uni Wien)
Abstract:The Local Group, our home galaxy group, consists of two large galaxies, the Milky Way and M31 (Andromeda Galaxy), and about 40 known galaxies. The starting point of the investigation is the observed distribution of the galaxies in the Local Group, which differs from our expectations. The problem is that most galaxies in our galaxy group are arranged in a quite thin plane which does not correspond to the disc-plane of one of the two dominant spiral galaxies. A possible explanation for the observed distribution is an interaction of the Milky Way and M31 about 10 to 12 Gigayears ago. At this time gas from outer parts of the galaxies has been scattered in the orbital plane of these two galaxies. It is investigated for which members of the Local Group this model is realistic and to reproduce the results of Sawa and Fujimoto in 2005. Since the orbits of dwarf galaxies around the host galaxies are sensitive to the shape of the host’s potential and to dynamical friction. So the dynamics of the Local Group are a perfect laboratory to test the Dark Matter paradigm and also an alternative theory, which is called MOdified Newtonian Dynamics (MOND). In this theory the law of gravitation is modified for small accelerations which occur in the outer parts of galactic discs and also in a galaxy group. In order to do this, stellar dynamical numerical simulations using newly developed software were run. The programmes were capable of performing n-body calculations with Newtonian gravity (and Dark Matter halos) or deep-MOND gravity, Hubble expansion and dynamical friction (only in the case of Newtonian gravity). The initial conditions of the models are optimised using a genetic algorithm until the distribution after the integration is sufficiently close to the observed distribution. The results are very multifarious, in some aspects also surprising and show that the model is possible in the case of Newtonian gravity but it has significant problems in MOND.
Date: Tue, 12.10.2010
Time: 12:00
Duration: 60 min
Location:TU Wien ( Wiedner Hauptstr. 8-10, yellow area, 10th floor, seminar room E136 )
Contact:Niklas Johansson

Spectral Minimal Partitions
Speaker:Thomas Hoffmann-Ostenhof (Univ.Wien) (Fakultät für Physik)
Abstract:im Rahmen des Seminars für Mathematische Physik
Date: Tue, 12.10.2010
Time: 14:15
Duration: 60 min
Location:Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock, 1090 Wien
Contact:J. Yngvason

Water Dissociation on Modified Transition Metal Surfaces
Speaker:Prof. Dr. Georg Held (Department of Chemistry, University of Reading, UK)
Abstract:Water dissociation on surfaces of late transition metals has been a topic of intense discussion in the last few years [1-4]. It is remarkable in this context that different members of the Pt group, which normally show very similar chemical behaviour, cause water to react in very different ways. This is mainly caused by electronic differences, affecting the balance between inter-molecular hydrogen bonds and water-substrate bonds. Atomic or molecular co-adsorbates are convenient means of modifying both types of bonds and were used in a systematic study to study this effect further. We compare the reactivity of water on clean and O-modified Pd{111}, Ir{111}, Pt{111}, Rh{111} and Ru{0001} using LEED, TPD, high resolution XPS and NEXAFS. All five surfaces have the same surface symmetry and very similar lattice constants. Except for Ru{0001} and Rh{111}, no dissociation is observed on the clean surfaces, even after prolonged irradiation with X-rays. Small amounts of oxygen, however, cause water to dissociate forming mixed (OH+H2O) layers on all surfaces, whereas high oxygen coverages (> 0.25ML) tend to leave water intact with more stable surface bonds than for the clean surfaces [5,6]. On Pt{111} and Ir{111} the maximum oxygen coverage is 0.25 ML and dissociation is observed for all coverages. Molecular co-adsorbates, such as CO and methanol tend to inhibit water dissociation at low temperatures. Possible geometrical effects were investigated using Pt{111}, {110} and {531}, these surfaces represent a series with increasing atomic roughness and coordination numbers decreasing from 9 to 6. No dissociation is observed on any of the clean surfaces but small amounts of oxygen promote water dissociation on all three surfaces. High coverages (exceeding half the saturation coverage) prevent water dissociation on Pt{531} and Pt{110}, but not on Pt{111}. [1] A. Thiel, T.E. Madey, Surf. Sci. Rep. 7 (1987) 211; [2] M.A. Henderson, Surf. Sci. Rep. 46 (2002) 1. [3] A. Hodgson, S. Haq, Surf. Sci. Rep. 64 (2009) 381. [4] P.J. Feibelman, Science 295 (2002) 58. [5] M.J. Gladys, et al. Chem. Phys. Lett. 414 (2005) 311. [6] A. Shavorskiy et al. PCCP 10 (2008) 6150
Date: Tue, 12.10.2010
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:Univ.Prof. Dr. Ulrike Diebold

Helpful tools in finite group theory
Speaker:Patrick Ludl (Univ.Wien) (Fakultät für Physik)
Abstract:im Rahmen des Teilchenphysikseminars
Date: Tue, 12.10.2010
Time: 16:15
Duration: 60 min
Location:Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock, 1090 Wien
Contact:W. Grimus, H. Neufeld

From Belle to Belle II
Speaker:Peter Krizan (Ljubljana University and J. Stefan Institute)
Abstract:The seminar will first review some recent highlights of measurements of B and D meson properties that have been carried out by the Belle collaboration. We will discuss the motivation for a future Super B factory at KEK, as well as the requirements for the detector. Finally, the present status of the project will be presented together with the plans for the future.
Date: Thu, 14.10.2010
Time: 16:00
Duration: 60 min
Location:SMI, Seminar room, Boltzmanngasse 3, 1090 Wien, Room 2.08
Contact:Roland Gsell

Spectral fits for the solar neutrino experiments BOREXINO and LENA
Speaker:Felicitas Thorne (University of Technology, Munich/Germany)
Abstract:The solar neutrino experiment BOREXINO, which is based on a 300 t liquid scintillator detector and detects neutrinos via neutrino-electron scattering, is located at the Laboratori Nazionali del Gran Sasso (LNGS). It was the first experiment to be able detecting solar neutrinos below 1 MeV. The main focus of this talk is the challenging task of separating between background and neutrino recoil events in data analysis. While some background (i.e muons) can be tagged event-by-event, beta decay events cannot be distinguished from neutrino-electron scattering. Therefore neutrino spectra and beta decays have to be fitted simultaneously. In this talk the approach of performing spectral fits and the current status of the work concerning reduction of the background (11C, 10C, 210Bi) to the pep/CNO neutrino search will be shown. Furthermore this technique will be applicable in association with neutrino oscillometry in LENA (Low Energy Neutrino Astronomy), a next-generation neutrino experiment which is based on a 50 kton target of liquid scintillator.
Date: Fri, 15.10.2010
Time: 14:00
Location:Institut für Hochenergiephysik, Nikolsdorfergasse 18, 1050 Wien, Bibliothek 1. Stock
Contact:Ch. Schwanda