Calendar of Physics Talks Vienna

Topological Gravity as the Early Phase of our Universe
Speaker:Prateek Agrawal (Oxford U.)
Abstract:I will present a scenario motivated by string dualities and the swampland where the early universe is described by a topological phase of gravity. Many cosmological puzzles can be explained in terms of the topological nature of this phase. To obtain phenomenological predictions, a concrete realization of this scenario using Witten's four dimensional topological gravity will be presented. In this model, the CMB power spectrum is controlled by conformal anomaly coefficients. The model predicts the absence of tensor modes in the CMB fluctuations and significant non-Gaussianities in 4- and higher point functions.
Date: Tue, 26.01.2021
Time: 14:00
Duration: 60 min
Contact:Céline Zwikel

Dark portals at direct detection
Speaker:Leonie EINFALT (Uni Wien and HEPHY, Vienna)
Abstract:Despite intense efforts in the experimental frontier, determining the nature of dark matter remains to be one of the unsolved problems in the 21st century. Among the ways to search for dark matter, direct detection experiments are an important avenue. In the context of direct detection, we explore scenarios where a dark matter particle interacts with Standard Model particles via two mediators. Both vector and scalar mediators, as well as mixtures thereof, are considered with one mediator being heavier than the other one in all cases. Adding a second mediator to the dark matter - Standard Model interaction leads to interference terms in the cross sections. We investigate novel signatures emerging from such complex phenomenology in the form of the shape of differential recoil spectra and exclusion limits at current and future low-threshold dark matter direct detection experiments.
Date: Tue, 26.01.2021
Time: 16:00
Duration: 60 min
Location:The seminars start at 16:15 but the meetings will be open already at 16:00. The link will be provided via email by Simon Plätzer (simon.plaetzer@univie.ac.at)
Contact:A. Hoang, M. Procura, S. Plätzer

Limits of JT gravity
Speaker:Jakob Salzer (Harvard)
Abstract:Jackiw—Teitelboim (JT) gravity is a model of two-dimensional dilaton gravity that has been central to many interesting developments (e.g., SYK model, random matrix models, island proposal) in the last couple of years. In this talk I will discuss various limits of JT gravity, including Newton—Cartan (non-relativistic) and Carrollian (ultra-relativistic) versions of two-dimensional dilaton gravity. After defining suitable boundary conditions, I will then discuss the issue of constructing boundary actions that capture the non-trivial dynamics at the boundary of these models.
Date: Thu, 28.01.2021
Time: 16:30
Duration: 60 min
Contact:Laura Donnay

Gravitational coupling of microscopic source masses: challenges for future quantum Cavendish experiments
Speaker:Markus Aspelmeyer (Universität Wien)
Abstract:No experiment today provides evidence that gravity requires a quantum description. It has been suggested that one can at least exclude the possibility for semiclassical gravity by performing an experiment whose outcome cannot be explained by a purely classical mass configuration. It turns out that such “quantum Cavendish” experiments are challenging, to say the least. I highlight some of the practical aspects of this challenge using the concrete example of our recent measurement of the gravitational field of a 1mm gold sphere, the smallest source mass to date in table-top gravity experiments.
Date: Fri, 29.01.2021
Time: 10:00
Duration: 45 min
Contact:Jörg Schmiedmayer