CPT

Calendar of Physics Talks Vienna

Coherence effects in light transport: Dicke vs Anderson localization
Speaker:Robin Kaiser (CNRS)
Abstract:The quest for Anderson localization of light is at the center of many experimental and theoretical activities. Cold atoms have emerged as interesting quantum system to study coherent transport properties of light. Initial experiments have established that dilute samples with large optical thickness allow studying weak localization of light. The goal of our research is to study coherent transport of photons in dense samples. One important aspect is the quest of Anderson localization of light with cold atoms and its relation to Dicke super- or subradiance. With large and dense samples of cold atoms the interplay between these different phenomena can be studied. In this talk I will give an overview on our research and present results on cooperative scattering of light by cold atoms.
Date: Mon, 26.03.2012
Time: 17:30
Duration: 60 min
Location:TU Wien, Schütte-Lihotzky Hörsaal, HS 7, Karlsplatz 13, 1040 Wien
Contact:Dr. Christiane Losert / Univ. of Vienna

Preparing projected entangled pair states on a quantum computer
Speaker:Martin Schwarz (University of Vienna)
Abstract:We present a quantum algorithm to prepare injective PEPS on a quantum computer. To be efficient, our algorithm requires well-conditioned PEPS projectors and, essentially, an inverse-polynomial spectral gap of the PEPS' parent Hamiltonian. Injective PEPS are the unique groundstates of their parent Hamiltonians and capture groundstates of many physically relevant many-body Hamiltonians, such as e.g. the 2D AKLT state. Even more general is the class of G-injective PEPS where symmetry group G acting on virtual tensor indices leaves the PEPS invariant. G-injective PEPS are powerful enough to represent topologically ordered quantum states. As our second result we show how to prepare G-injective PEPS under similar assumptions as well.
Date: Tue, 27.03.2012
Time: 12:30
Duration: 60 min
Location:Vienna University of Technology: Wiedner Hauptstr. 8-10, 10th floor (yellow), seminar room E136
Contact:Vienna Theory Lunch Seminar (http://www.univie.ac.at/lunch-seminar/)

Störungstheoretische AQFT: Ein erster Überblick über Störungstheorie II
Speaker:Jan Schlemmer (Univ. Wien)
Abstract:im Rahmen des Seminars für Mathematische Physik
Date: Tue, 27.03.2012
Time: 14:15
Duration: 60 min
Location:Fakultät für Physik, Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock, 1090 Wien
Contact:J. Yngvason

Existence of time functions
Speaker:Albert Fathi (ENS Lyon, et Inst. Univ. de France)
Abstract:im Rahmen des Literaturseminars
Date: Thu, 29.03.2012
Time: 14:15
Duration: 60 min
Location:Arbeitsgruppe: Gravitation, Währinger Strasse 17, Seminarraum A, 2. Stock
Contact:R. Beig

Linking models with data: the Nelder-Mead method
Speaker:Patrick Ludl (Univ.Wien)
Abstract:im Rahmen des Teilchenphysikseminars
Date: Thu, 29.03.2012
Time: 14:15
Duration: 60 min
Location:Fakultät für Physik, Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock, 1090 Wien
Contact:W. Grimus, H. Neufeld

Moving Quark in a Viscous Fluid
Speaker:Ali Davody (IPM Teheran)
Abstract:After reviewing basic aspects of Fluid/Gravity correspondence and holographic computation of drag force exerted on a quark moving through an N=4 SYM, we study the rate of energy loss of a heavy quark in the hydrodynamic regime. We use fluid/gravity duality and construct a perturbative procedure to find the string solution in gravity side. We apply this procedure to a transverse quark in Bjorken flow and compute viscous corrections to the drag force.
Date: Thu, 29.03.2012
Time: 16:00
Duration: 60 min
Location:SEM 136 (Freihaus, Wiedner Hauptstrasse 8-10), Institute for Theoretical Physics, Vienna University of Technology
Contact:Daniel Grumiller

Emergence of Ornstein-Uhlenbeck processes from large mechanical system with random initial data
Speaker:Maximilian Sadilek (Univ. Wien)
Abstract:im Rahmen der gemeinsam veranstalteten Seminare "Komplexe Stochastische Systeme" (Univ.Wien) und "Analyse Komplexer Systeme" (Med.Univ.Wien)
Date: Fri, 30.03.2012
Time: 14:00
Duration: 60 min
Location:Fakultät für Physik, Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock, 1090 Wien
Contact:H. Hüffel, Stefan Thurner

White noise limits of multiplicative colored noise
Speaker:Florentin Harbich (Univ.Wien)
Abstract:im Rahmen der gemeinsam veranstalteten Seminare "Komplexe Stochastische Systeme" (Univ.Wien) und Analyse Komplexer Systeme" (Med.Univ.Wien)
Date: Fri, 30.03.2012
Time: 15:15
Duration: 60 min
Location:Fakultät für Physik, Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:H. Hüffel, Stefan Thurner

Nonthermal fixed points, topological excitations, and superfluid turbulence in an ultracold Bose gas
Speaker:Thomas Gasenzer (Universität Heidelberg )
Abstract:Turbulence appears in situations where, e.g., an energy flux goes from large to small scales where finally the energy is dissipated. As a result the distribution of occupation numbers of excitations follows a power law with a universal critical exponent. The situation can be described as a nonthermal fixed point of the dynamical equations. Single-particle momentum spectra for a dynamically evolving Bose gas are analysed using semi-classical simulations. These give information about possible universal scaling behaviour. The connection of this scaling with the appearance of topological excitations such as solitons and vortices is discussed. For the one-dimensional case, a random-soliton model provides analytical results for the spectra, and their relation to those found in a field-theory approach to strong wave turbulence is discussed. The results open a view on solitary wave dynamics from the point of view of critical phenomena far from thermal equilibrium and on a possibility to study this dynamics in experiment without the necessity of detecting solitons in situ.
Date: Fri, 30.03.2012
Time: 15:30
Location:Seminarraum Atominstitut
Contact:Eva Haberl, Atominstitut