Calendar of Physics Talks Vienna

The Milky Way satellite galaxies - a serious challenge for the Cold Dark Matter cosmology
Speaker:Gerhard Hensler (Vienna)
Abstract:The so-called cosmological concordance model of a Cold Dark Matter (CDM) dominated universe predicts a huge number of low-mass CDM subhalos to exist and to surround massive galaxies with an almost isotropic distribution. For our Milky Way and the neighboring Andromeda galaxy these both requirements are significantly contrasted by observations. Not only that the observed number of satellite galaxies is orders of magnitude smaller - the so-called missing-satellite problem – moreover, their spatial distributions are confined to thin planes with coherent orbits. Nevertheless, unusually high mass-to-light ratios are derived for the dwarf spheroidal galaxies around the Milky Way, lending strong support of their large CDM content. In order to approach consistency of the observational restrictions with the CDM cosmology, over the recent years various scenarios are constructed ....
Date: Thu, 08.01.2015
Time: 14:00
Duration: 60 min
Location:Arbeitsgruppe Gravitation, Währinger Strasse 17, Seminarraum A, 2. Stock, 1090 Wien
Contact:P.T. Chrusciel

Improving CKM Unitarity Limits via Low-Energy Nuclear Physics
Speaker:Paul E. J. Finlay (KU Leuven)
Abstract:If the current three-generation standard model is complete, then the Cabibbo-Kobayashi-Maskawa matrix, which relates the mass and weak-interaction eigenstate of the quarks, should be unitary. The strictest test of unitarity currently comes from the top-row sum, with the most precise value for the largest element, Vud, coming from superallowed Fermi beta decays. The primary challenge towards future progress in CKM unitarity tests lies with understanding the theoretical isospin-symmetry-breaking (ISB) corrections, which currently dominate the uncertainty in the superallowed Ft values. Experimental input for the improvement of these calculations is possible, and this seminar will highlight some current and proposed low-energy nuclear physics experiments aiming to contribute to the understanding and refinement of the ISB corrections.
Date: Thu, 08.01.2015
Time: 15:30
Location:Atominstitut, Stadionallee 2, Wien 2, Hörsaal
Contact:H. Abele

An introduction to Vlasov fields
Speaker:Jeremie Joudioux (University of Vienna)
Abstract:The Einstein-Vlasov system is a good model to study the large scale behavior of our universe. After presenting the model in detail, I will describe the underlying geometry of the Einstein-Vlasov system, with a focus on how the symmetries of the spacetime lift up to symmetries of Vlasov fields. In the final section, the Cauchy problem for the Einstein-Vlasov system will be shortly presented, and the methods which are used to tackle the global existence and the stability of solutions will be shortly introduced.
Date: Thu, 08.01.2015
Time: 16:00
Duration: 60 min
Location:SEM 136, TU Wien, Freihaus, 10th floor (Wiedner Hauptstr. 8-10, A-1040 Vienna)
Contact:Daniel Grumiller and Johanna Knapp

Covariant loop quantum gravity
Speaker:Wolfgang Wieland (Pennsylvania State University)
Abstract:The talk gives an introduction to covariant loop quantum gravity, and presents recent developments in the field. The kinematical Hilbert space is derived from Ashtekar’s reformulation of general relativity in terms of SU(2) Yang—Mills variables. Quantum states of geometry live on the boundary of spacetime. Areas, angles and volumes turn into operators with discrete spectra. The dynamics is given in terms of spinfoam amplitudes, which represent the continuation of spin-network boundary states into the bulk. The most crucial open problem concerns the semi-classical limit: How can we recover general relativity plus quantum corrections? Studying this question, I found a proposal for a new action for discretized gravity in terms of spinors [arXiv:1407.0025]. The action is a one-dimensional line integral over the edges of the discretization, and these edges turn into the worldlines of a system
Date: Fri, 09.01.2015
Time: 15:15
Duration: 60 min
Contact:Nils Carqueville