CPT

Calendar of Physics Talks Vienna

Loop Quantum Gravity and the Continuum
Speaker:Wolfgang Wieland (Perimeter Institute for Theoretical Physics, Waterloo, Canada)
Abstract:One of the main open problems in loop quantum gravity is to reconcile the fundamental quantum discreteness of space with general relativity in the continuum. In this talk, I present recent progress regarding this issue: I will explain, in particular, how the discrete spectra of geometric observables that we find in loop gravity can be understood from a conventional Fock quantisation of gravitational edge modes on a null surface boundary. On a technical level, these boundary modes are found by considering a quasi-local Hamiltonian analysis, where general relativity is treated as a Hamiltonian system in domains with inner null boundaries. The presence of such null boundaries requires then additional boundary terms in the action. Using Ashtekar’s original SL(2,C) self-dual variables, I will explain that the natural such boundary term is nothing but a kinetic term for a spinor . . . .
Date: Tue, 13.11.2018
Time: 13:45
Duration: 60 min
Location:TU Wien, Getreidemarkt 9, Maschinenbaugebäude, 1. Stock, HS Kleiner Schiffbau
Contact:S. Fredenhagen, D. Grumiller

Surface forces and nanoscale alignment of anisotropic fluids probed with the Surface Force Apparatus
Speaker:Bruno Zappone (Consiglio Nazionale delle Ricerche – Istituto di Nanotecnologia, c/o Universitá delle Calabria, Rende (CS)/Italy)
Abstract:Soft anisotropic materials that change their macroscopic properties in response to external stimuli such as electric field, light, heat or mechanical stress are central to several new directions of technology, including optics, micro-mechanics and bioengineering. The Surface Force Apparatus (SFA) is a powerful tool for investigating such materials at the nanometer scale and reveal the fundamental link between microscopic anisotropic order and macroscopic response. We recently developed a new method for analyzing the complex multiple-beam interference patterns arising from optically anisotropic multilayers in SFA experiments. We demonstrated that the method can be used to accurately measure both the thickness and twist angle of a nematic liquid crystal (LC) layer confined under twist-inducing parallel boundary conditions, and characterize the electro-optical response of LC films as thin
Date: Tue, 13.11.2018
Time: 16:00
Location:TU Wien, Institut für Angewandte Physik, E134 1040 Wien, Wiedner Hauptstraße 8-10 Yellow Tower „B“, 5th floor, SEM.R. DB gelb 05 B
Contact:Univ.Prof. Markus Valtiner

Double parton scattering: basics and recent theory developments
Speaker:Markus Diehl (DESY, Hamburg)
Abstract:im Rahmen des Teilchenphysikseminars: I give a brief introduction into the double parton scattering mechanism in proton-proton collisions, and then discuss several advances in their theoretical description. Aspects to be discussed are factorisation, evolution, and the distinction between single and double hard scattering.
Date: Tue, 13.11.2018
Time: 16:15
Duration: 60 min
Location:Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:A. Hoang, S. Plätzer

Semiclassical perspective on strong-field photoelectron holography
Speaker:Nikolay Shvetsov-Shilovskiy (Leibniz Universität Hannover)
Date: Thu, 15.11.2018
Time: 11:15
Location:Seminar room FH gelb 10, Institute for Theoretical Physics – Vienna University of Technology, Wiedner Hauptstraße 8 – 10, 10th floor, B (yellow tower)
Contact:Joachim Burgdörfer

The Friedrich-Butscher method for the construction of initial data in General Relativity
Speaker:Jarrod Williams (ESI)
Abstract:im Rahmen des Literaturseminars für Gravitationsphysik: The construction of initial data for the Cauchy problem in General Relativity is an interesting problem from both the mathematical and physical points of view. As such, there have been numerous methods studied in the literature - the "Conformal Method" of Lichnerowicz-Choquet-Bruhat-York and the "gluing" method of Corvino-Schoen being perhaps the best-explored. In this talk I will describe an alternative, perturbative, approach proposed by A. Butscher and H. Friedrich, and show how it can be used to construct non-linear perturbations of initial data for spatially-closed analogues of the "k = -1" FLRW spacetime. Time permitting, I will discuss possible refinements/extensions of the method, along with its generalisation to the full Conformal Constraint Equations of H. Friedrich.
Date: Thu, 15.11.2018
Time: 14:00
Duration: 60 min
Location:Arbeitsgruppe Gravitation, Währinger Strasse 17, Raum 218, 2. Stock, 1090 Wien
Contact:P.T. Chrusciel, D. Fajman