Calendar of Physics Talks Vienna

Toward massless and massive Event Shapes in the large-$\beta_0$ limit
Speaker:Néstor González Gracia (Universidad de Salamanca)
Abstract:The strong coupling and the top quark mass are among the most important parameters in the Standard Model and measurements with higher-than-current precision will be pursued at future linear colliders.Effective Field Theories provide a framework for efficiently organizing the computations relevant in this context,such as SCET and HQET. Two related aspects that deserve attention are the convergence of perturbative expansions and the size of nonperturbative corrections,that can be studied within the framework of renormalons. In this talk we present all-order results for SCET and bHQET matching coefficients and jet functions in the large-$\beta_0$ limit,as well as for their anomalous dimensions. We also study the MSR short-distance low-scale mass in this limit. Our results point to a possible solution for a long-standing problem with the normalization of differential cross sections for ...
Date: Tue, 20.04.2021
Time: 14:00
Duration: 60 min
Location:ZOOM: https://univienna.zoom.us/j/93104933847?pwd=N0FrL0E1UHlkQWRhQTlQODVkZ3kvUT09 Meeting ID: 931 0493 3847 Passcode: 674625
Contact:A. Hoang, P. Stoffer

Resurgence and BPS invariants
Speaker: Jie Gu (Geneva University)
Abstract:Asymptotic series abound in physics. Borel resummation and resurgence theory are among the powerful tools to deal with them. The former provides a way to convert asymptotic series to numbers, the latter reveals that different asymptotic series at different saddle points are related to each other by Stokes automorphism characterised by Stokes constants. We argue that the Stokes constants can be treated as new invariants of the system, and in many cases can be interpreted as counting BPS states. We support this statement with examples in Seiberg-Witten theory, complex Chern-Simons theory, and topological string theory.
Date: Tue, 20.04.2021
Time: 14:00
Duration: 60 min
Location:Zoom: https://moodle.univie.ac.at/mod/bigbluebuttonbn/guestlink.php?gid=x8o6ILSKJuC9
Contact:S. Fredenhagen, D. Grumiller, T. Schimannek

Non-singular global Kerr-NUT-(A)dS spacetimes
Speaker:Jerzy Lewandowski (Warsaw)
Abstract:The outstanding issue of a non-singular extension of the Kerr-NUT-(anti) de Sitter solutions to Einstein's equations is solved completely. The Misner's method of obtaining the extension for Taub-NUT spacetime is generalized in a non-singular manner. The Killing vectors that define non-singular spaces of non-null orbits are derived and applied. The global structure of spacetime is discussed. The non-singular conformal geometry of the null infinities is derived. The Killing horizons are present.
Date: Thu, 22.04.2021
Time: 15:00
Duration: 60 min
Location:ZOOM: https://univienna.zoom.us/j/6540036841?pwd=SytyVkZJZzNyRG9lMm13ejlHeHRRUT09
Contact:Piotr Chrusciel, David Fajman

BMS symmetry in light-cone gravity
Speaker:Sucheta Majumdar (Université Libre de Bruxelles)
Abstract:The aim of this talk is to discuss how the BMS symmetry appears in gravity in the light-cone gauge, a formulation where all unphysical degrees of freedom are integrated out. By checking the invariance of the light-cone Hamiltonian, we obtain a set of residual gauge transformations that satisfy the BMS algebra realized on the two physical fields in the theory. Hence, the BMS algebra appears as a consequence of residual gauge invariance in the bulk without any reference to asymptotic limits. Alternatively, one can also obtain the BMS algebra as a local extension of the Poincaré symmetry in light-cone gravity in four dimensions. In the light-cone formalism, the dynamical part of the Poincaré algebra is enhanced to accommodate the supertranslations, yielding the infinite-dimensional BMS algebra.
Date: Thu, 22.04.2021
Time: 16:30
Duration: 60 min
Contact:Laura Donnay

Light-induced dipole-dipole interactions in a dense BEC: theory and experiment
Speaker:Matthias Sonnleitner (Universität Innsbruck)
Abstract:The interaction between light and a dense cloud of atoms is like a ping-pong between action and back-action: light induces dipoles, the dipoles interact with each other and collectively they reshape of the light field. We discuss the theoretical basis of light-induced dipole-dipole interaction and how an experiment at the Atominstitut is testing the limits of this theory.
Date: Fri, 23.04.2021
Time: 14:00
Duration: 45 min
Contact:Philipp Haslinger