CPT

Calendar of Physics Talks Vienna

Spontaneous symmetry breaking and Nambu-Goldstone bosons: some news in the old story
Speaker:Tomas Brauner (University of Helsinki)
Abstract:The concept of spontaneous symmetry breaking is key to understanding of a vast range of physical phenomena such as superfluidity, ferromagnetism, or the origin of masses of elementary particles. I will provide a brief introduction to this classic topic and then review some recent results: (i) Completed classification and counting of Nambu-Goldstone bosons; (ii) A new class of states protected by symmetry: the massive Nambu-Goldstone bosons. I will conclude by outlining some yet unresolved problems, relevant for applications to a variety of quantum many-body systems.
Date: Mon, 02.12.2013
Time: 16:00
Duration: 60 min
Location:Vienna University of Technology, Wiedner Hauptstr. 8-10, yellow area, 10th floor, seminar room E136
Contact:Andreas Schmitt

Monte Carlo Simulations in Statistical Physics: Theory and Applications
Speaker:Christian Leitold (University of Vienna)
Abstract: In statistical mechanics, many quantities of interest, like a system's energy as a function of temperature, are given as a high dimensional integral in the configuration space of the system which cannot be evaluated directly. However, it is possible to approximate this integral by a sequence of random samples, distributed according to the underlying probability distribution, e. g. the Boltzmann distribution in the case of a system with fixed temperature, volume and particle number. One way to generate such a sequence is the Metropolis algorithm. In my talk, I will present the theoretical background of this algorithm and give a few examples of its applications in the field of soft and condensed matter simulations. This applications range from comparatively easy systems like the Lennard-Jones fluid to more complex cases like the sampling of typical folding pathways in a model protein.
Date: Tue, 03.12.2013
Time: 12:30
Duration: 60 min
Location:Univ. of Vienna, Faculty of Physics, Boltzmanngasse 5, 5th floor, Erwin Schrödinger Lecture Hall
Contact:Albert Georg Passegger, Peter Poier - www.univie.ac.at/lunch-seminar

Every atom counts: Controlling chemical processes in single molecules on surface
Speaker:Prof. Dr. Leonhard Grill (Department of Physical Chemistry, University of Graz)
Abstract:A fundamental understanding of functional molecules and their assembly into pre-defined architectures are key challenges in nanotechnology and of interest in various fields from molecular electronics over novel materials to molecular machines. We study chemical processes of single functional molecules on surfaces by scanning tunneling microscopy under ultrahigh vacuum conditions and at low temperatures, thus allowing submolecular resolution analysis. Various examples of how to control chemical processes will be discussed, ranging from covalent molecular linking to intramolecular reactions. The first is realized in on-surface polymerization processes where molecular building blocks are connected to two-dimensional networks or one-dimensional chains, which can act as molecular wires. On the other hand, chemical processes within individual molecular can be controlled via their environment.
Date: Tue, 03.12.2013
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

Gravity, dark energy and dark matter from quantum information
Speaker:Erik VERLINDE (Institute for Theoretical Physics, University of Amsterdam)
Abstract:I will give an overview of recent developments that relate quantum information, in particular the notion of entanglement entropy, to the origin of gravity. Black hole physics and string theory give important hints and constraints on the microscopic description of the underlying degrees of freedom. Extending these ideas to cosmology leads to a new view on dark energy, and even explains quantitative features of dark matter.
Date: Wed, 04.12.2013
Time: 16:00
Location:TU Wien Atominstitut, Seminarraum, Stadionallee 2, 1020 Wien
Contact:J. Schmiedmayer

P and T violation in heavy atoms
Speaker:Lorenz Willmann (University of Groningen, The Netherlands)
Abstract:Searches for violations of the fundamental discrete symmetries parity (P), time reversal (T) and charge conjugation (C) provide guidelines for model building beyond the Standard Model of the electroweak interactions (SM). Here, experiments are performed on many different energy scales. At low energies searches for permanent electric dipole moments (EDMs) have a robust discovery potential while measurements of atomic parity violation (APV) test the electroweak interactions. These effects are strongly enhanced in heavy atomic systems and they become accessible in precision atomic physics experiment. The sensitivity of neutral radium towards EDMs arises from its nuclear and atomic structure which result radium offers the largest known atomic enhancement factors to nuclear and electron EDMs. Furthermore atomic parity violation can be measured in a single trapped radium ion. The precision de
Date: Wed, 04.12.2013
Time: 17:00
Duration: 60 min
Location:Stefan-Meyer-Institut, ÖAW, Seminar room, Boltzmanngasse 3, Room 2.08
Contact:Ken Suzuki

Bose-Einstein condensate in an optical cavity: exploring the Dicke-type quantum phase transition
Speaker:Peter DOMOKOS (Wigner Research Centre for Physics, Budapest, Hungary)
Abstract:The coherent coupling of a single mode of the resonator with motional excitations of a Bose-Einstein condensate driven by a laser perpendicular to the cavity axis was shown to be a formal realization of the Dicke model. This system led to the first observation of the phase transition in the Dicke model which is, in fact, the zero temperature limit of the atomic self-organization in a cavity. Beyond the mapping of the phase diagram, the spontaneous symmetry breaking as well as the mode softening in the excitations spectrum at the critical point have been demonstrated experimentally. The cavity-based realization is an open system, therefore the Dicke-type Hamiltonian does not provide for a complete description. The critical behavior has been reinvestigated for the stationary state of the driven and damped system. We will show that the non-equilibrium system exhibits a dynamical quantum phase transition. The critical point as well as the mean field solution are only slightly modified with respect to the equilibrium phase transition in the ground state. However, the correlation functions describing the quantum fluctuations differ significantly in the two, equilibrium and non-equilibrium, cases. Recent experiments revealed the importance of the atom-atom s-wave scattering in quantitative description of data. Here we will show that the damping of motional excitations is very sensitive to the coupling to a photon field and the Beliaev damping rate can be resonantly tuned by the external laser drive strength.
Date: Thu, 05.12.2013
Time: 11:00
Location:TU Wien Atominstitut, Hörsaal, Stadionallee 2, 1020 Wien
Contact:P. Rabl

Relativistic motion and self-interaction
Speaker:Abraham Harte (AEI Potsdam)
Abstract:im Rahmen des Literaturseminars für Gravitation
Date: Thu, 05.12.2013
Time: 14:15
Duration: 60 min
Location:Arbeitsgruppe: Gravitation, Währinger Strasse 17, Seminarraum A, 2. Stock
Contact:H. Rumpf

Maksimovic - The story of Bruno Pontecorvo
Speaker:Filmvorführung - Idee und Drehbuch: G. Mussardo (SISSA)
Abstract:im Rahmen des Teilchenphysikseminars
Date: Thu, 05.12.2013
Time: 14:15
Duration: 60 min
Location:Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:W. Grimus, H. Neufeld

Critical Collapse in the Axion-Dilaton system in type IIB and in diverse dimensions
Speaker:Ehsan Hatefi (ICTP Trieste)
Abstract:The talk is based on two different parts. First, based on arxiv:1108.0078 (Class. Quantum Grav. 29 (2012) 025006) we study the gravitational collapse of the axion-dilaton system suggested by type IIB string theory in dimensions ranging from four to ten. We extend previous analysis concerning the role played by the global SL(2,R) symmetry and we evaluate the Choptuik exponents in the elliptic case. In the second part of the talk (based on arxiv:1307.1378, JCAP 1310 (2013) 037), we complete our previous study of critical gravitational collapse in the axion-dilaton system by analysing the hyperbolic and parabolic ansätze. We also introduce a new method to obtain perturbations and how to explore the corresponding Choptuik exponents in four-dimensions which differs from the elliptic case.
Date: Thu, 05.12.2013
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

Mathematical formulation of multi-layer networks
Speaker:Anna Chmiel (Med.Univ.Wien)
Abstract:im Rahmen der gemeinsam veranstalteten Seminare "Komplexe Stochastische Systeme" (Univ.Wien) und "Analyse Komplexer Systeme" (Med.Univ.Wien)
Date: Fri, 06.12.2013
Time: 14:15
Duration: 90 min
Location:Medizinische Universität Wien, Informatikbibliothek, Bauteil 88, E03, Spitalgasse 23, 1090 Wien
Contact:H. Hüffel, Stefan Thurner