Calendar of Physics Talks Vienna

Using Matrix Product States to Classify Quantum Phases in (1+1)D (Vienna Theory Lunch Seminar)
Speaker: David Blanik (Universität Wien)
Abstract: Understanding the phase diagram of correlated quantum many-body systems is among the most important and most challenging tasks towards a comprehensive understanding of such systems. In this talk I will give a brief introduction to tensor networks and explain how to use tensor network methods, in particular Matrix Product States (MPS), to classify gapped quantum phases. Specifically, we will derive the well known classification of symmetry-protected topological (SPT) phases in (1+1)D. [[This talk is part of the "Vienna Theory Lunch Seminar", a weekly seminar aimed at both graduate and advanced undergraduate students, jointly organized by the University of Vienna and TU Wien. The focus of the seminar is on recent theoretical research done by Master students, PhDs and PostDocs. Free lunch (pizza) will be provided at the seminar. More information: https://lunch-seminar.univie.ac.at ]]
Date: Tue, 21.11.2023
Time: 12:30
Duration: 75 min
Location:Boltzmanngasse 5, 5th floor, Schrödinger Lecture Hall
Contact:Florian Lindenbauer

Ion-induced Nanopatterning: New Insights from in-situ X-Ray Scattering Studies and Numerical Simulations
Speaker:Stefan Facsko (Ion Beam Center, Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden/Germany)
Abstract:A plethora of self-organized nanoscale patterns emerge on surfaces which are irradiated by low-energy ion beams. Depending on the irradiation conditions, hexagonally ordered dot or pit patterns, checkerboard patterns, as well as periodic ripple patterns are formed spontaneously due to the non-equilibrium conditions induced by continuous ion irradiation. In-situ studies of the surface morphology can reveal the kinetics of the patterning process, yielding further insight into the dominant mechanisms and thus enabling to gain precise process control. For instance, by real-time in-situ Grazing Incidence Small Angle X-Ray Scattering (GISAXS) investigation the significant morphological parameters of the surface are deduced, thus tracking the development of the crystalline Ge(100) surface morphology during ion irradiation. Observing the kinetics of pattern formation in the non-linear regime, we
Date: Tue, 21.11.2023
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:Prof. Dr. Richard Wilhelm

Rigidity of extremal horizons and black hole uniqueness
Speaker: James Lucietti (Edinburgh)
Abstract:I will present a recent proof which shows that the intrinsic geometry of compact cross-sections of any vacuum extremal horizon, possibly with a cosmological constant, must admit a Killing vector field. In particular, this implies that the extremal Kerr horizon is the most general such horizon in four-dimensional General Relativity and completes the classification of the associated near-horizon geometries. I will also discuss a recent uniqueness proof which shows that any analytic Einstein spacetime, that contains a static extremal horizon with a maximally symmetric compact cross-section, is the extremal Schwarzschild de Sitter spacetime or its near-horizon geometry.
Date: Wed, 22.11.2023
Time: 14:15
Duration: 60 min
Location:Seminarraum A, Waehringer Straße 17, 2. Stock
Contact:P. Chrusciel, D. Fajman

Fiber Fabry-Pérot Fabrication for Enhanced Atom-Cavity Coupling
Speaker:Isabelle Safa (TU Wien, Atominstitut)
Abstract:Cold atoms are a leading platform for quantum computation thanks to their coherence properties, microscopic controllability, and scalability. While current quantum processors with neutral atoms are limited to local interactions, our experiment aims to reach programmable and large scale connectivity between Rubidium atoms by means of optical cavity-generated interactions. For this purpose, a small yet open cavity with compact mode geometry is required. Suitable devices are thereupon fiber Fabry-Pérot cavities (FFPC), the mirrors of which are directly machined on the end facets of two face-to-face optical fibers. These micrometer-scale, concave mirrors thus form a miniaturized Fabry-Pérot interferometer. In this talk, I will present the work done during my master thesis at the ATI in the group of Julian Léonard, in which I started to build a setup for this micro-mirror machining. The proce
Date: Wed, 22.11.2023
Time: 16:15
Duration: 45 min
Location:Helmut Rauch Hörsaal ATI
Contact:Julian Leonard

Speaker:Bharat Ratra (Kansas State University)
Abstract:Experiments and observations over the last two decades have provided strong support for a "standard" model of cosmology that describes the evolution of the universe from an early epoch of inflation to the complex hierarchy of structure seen today. I review the basic physics, astronomy, and history of ideas, on which this model is based. I describe the data which persuade cosmologists that (as yet not directly detected) dark energy and dark matter are by far the main components of the energy budget of the universe. I conclude with a list of open cosmological questions.
Date: Thu, 23.11.2023
Time: 17:00
Location:Technische Universitaet Wien, Freihaus, Hoersaal 5, Wiedner Hauptstrasse 8, 1040 Wien
Contact:Prof. Hartmut Abele

Quantum Field Simulator: From Cosmology via Ramsauer-Townsend Effect to Supersolids
Speaker:Markus Oberthaler (Universität Heidelberg)
Abstract:Recently it has been shown that two dimensional ultracold gases allow for the study of time dependent curved space-time of the form discussed in cosmology. With the assumption of homogeneity and isotropy of the universe the metric for large scale is given by the Friedmann-Lemaitre-Robertson-Walker metric, which is characterized via the sign of the curvature and a general scale factor. I will discuss how both, the curvature as well as the scale factor, are experimentally accessible with ultracold gases leading to curved trajectories as well as to particle production in an expanding universe [1]. How the particle production can be connected to the Ramsauer-Townsend effect will be presented and motivates the study of oscillating – expanding and compressing – universes. This regime leads to emergent non-linear structures of space-time indicating that backaction is already present in the expe
Date: Fri, 24.11.2023
Time: 10:00
Duration: 45 min
Location:Helmut Rauch Hörsaal ATI
Contact:Julian Leonard