Calendar of Physics Talks Vienna

The Role of Sources in Flat Space Holography (Vienna Theory Lunch Seminar)
Speaker: Adrien Fiorucci (TU Wien)
Abstract: The aim of this talk is to review the main obstacles to the construction of flat space holography on the basis of the celebrated AdS/CFT correspondence – namely the null nature of the conformal boundary and the non-conservation of gravitational charges in the presence of radiation – and to discuss how to deal with them. It will be argued that the putative holographic dual theory is a Carrollian conformal field theory, coupled to external sources that account for the radiation reaching the boundary. To formalise this coupling, a generalised concept of variational symmetries must be introduced, for which Noether’s first theorem yields flux-balance laws instead of conservation laws. Some implications of this new formalism will be discussed, both in classical mechanics and in quantum field theory. [[part of the "Vienna Theory Lunch Seminar, see https://lunch-seminar.univie.ac.at ]]
Date: Tue, 31.10.2023
Time: 12:30
Duration: 75 min
Location:TU Wien: Wiedner Hauptstr. 8-10, yellow area, 10th floor, seminar room DB10E11
Contact:Florian Lindenbauer

Topology change and heterotic flux vacua
Speaker:Ilarion Melnikov (James Madison Univ. / IPhT Saclay)
Abstract:I will review the status of heterotic flux compactification with 8 and 4 supercharges. The underlying geometry of these compactifications is a principal torus bundle over a K3 surface, and T-duality in the torus fiber leads to equivalences between topologically distinct configurations. In particular, I will argue that all such vacua that preserve 8 supercharges can be related to more conventional (flux free) compactifications. These dualities lead to a rich interconnected web of stringy geometries with a fairly direct worldsheet CFT interpretation. Orbifolds of such configurations can partially break supersymmetry and reduce the gauge group rank. On the other hand, there are four-dimensional configurations that cannot be T-dualized to configurations without flux; these configurations place strong constraints on the underlying K3 geometry.
Date: Tue, 31.10.2023
Time: 14:00
Duration: 60 min
Location:Sem. R. DB gelb 03 - TU Wien Freihaus, Wiedner Hauptstrasse 8, 3rd floor, yellow tower
Contact:S. Fredenhagen, D. Grumiller, T. Tran, A. Fiorucci

Structure of epitaxial thin oxide films investigated in situ by x-ray diffraction using synchrotron radiation
Speaker:Maurizio De Santis (Institut Néel, CNRS, Université Grenoble Alpes, Grenoble/France)
Abstract:Combining Grazing Incidence X-Ray Diffraction (GIXRD) and X-Ray Reflectivity (XRR) allows to solve the structure of crystal surfaces and epitaxial ultrathin films, and to investigate thin films growth. After a general introduction to the technique, I will show some studies of oxide films. The first example concerns the growth mode and the structure of an ultrathin MgO film on Ag(001). MgO ultrathin films are employed as decoupling layers between metallic substrates and electronic states of molecules or atoms deposited on top. In the following I will discuss the growth of CuO and TiO2-anatase films on SrTiO3(001), both obtained through a post-deposition annealing in oxygen. These films are investigated for their multiferroic and catalytic properties, respectively. The measurements I will show were performed on the French BM32 beamline at the European Synchrotron Radiation Facility (ESRF).
Date: Tue, 31.10.2023
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:Ao.Univ.Prof. Dr. Michael Schmid