Calendar of Physics Talks Vienna

Growth, Distribution, and Photosynthesis of Chlamydomonas Reinhardtii in 3D Hydrogels
Speaker:Jeong-Joo Oh (Delft University of Technology, The Netherlands)
Abstract:Engineered living materials (ELMs) are emerging class of functional materials, often fabricated by incorporating living cells within an inert polymer matrix to form desired functions. Photosynthetic microorganisms can be integrated into polymeric matrices to form ELMs with plant-like qualities, allowing them to photosynthesize and thus to provide a localized O2 source and/or CO2 sink. Unraveling the formation, spatial localization, and behavior of photosynthetic cell populations within an artificial niche is a prerequisite for predicting and intensifying the functions of living materials. Our group focuses on the growth and spatial distribution of eukaryotic microalgae Chlamydomonas reinhardtii within hydrogel networks for the strategic fabrication of living materials with intensified CO2 capture. Existing unicellular microalgae within scaffolds form multicellular algal aggregates, calle
Date: Tue, 12.03.2024
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. R.A. Wilhelm

On staticity of bifurcate Killing horizons
Speaker:Marc Mars (U of Salamanca)
Abstract:In this talk I will study the necessary and sufficient conditions that a spacetime admitting a bifurcate Killing horizon must satisfy to be static, i.e. such that the Killing of the horizon is hypersurface orthogonal. The result involves a bulk condition on the Ricci curvature, which is automatically satisfied for $\Lambda$-vacuum spacetimes, and a boundary condition on the data at the bifurcation surface. The problem is solved in arbitrary dimension, and requires a different treatment in the region where the Killing is timelike (the exterior of the horizon) or spacelike (inside the horizon). This is joint work with Piotr. T. Chrusciel.
Date: Wed, 13.03.2024
Time: 14:15
Duration: 60 min
Location:Seminarraum A, Waehringer Strasse 17, 2nd Floor
Contact:P. Chrusciel

An exciting hint towards the solution of the neutron lifetime puzzle?
Speaker:Ben Koch (TU Wien, Atominstitut)
Abstract:We revisit the neutron lifetime puzzle, a discrepancy between beam and bottle measurements of the weak neutron decay. Since both types of measurements are realized at different times after the nuclear production of free neutrons, we argue that the existence of an excited state could be responsible for the different lifetimes. We elaborate on the required properties of such a state and construct a concrete toy model with several of the required characteristics.
Date: Wed, 13.03.2024
Time: 16:15
Duration: 45 min
Location:Helmut Rauch Hörsaal ATI
Contact:Maximilian Prüfer

Probing electronic band topology by magneto-optics
Speaker:Istvan Kezsmarki (Augsburg University)
Abstract:Giant anomalous Hall effect (AHE) and magneto-optical activity can emerge in magnets with topologically non-trivial degeneracies. However, identifying the specific band structure features like Weyl points, nodal lines or planes which generate the anomalous response is a challenging issue, requiring reliable spectroscopic techniques. Since the low-energy interband transitions can govern the static AHE, we address this question in prototypical magnetic Weyl semimetals Co3Sn2S2 and Fe3Sn2. We show that magneto-optical spectroscopy, in combination with material-specific theory, can reveal Berry phase hot spots in the Brillouin zone and relate the optical Hall effect to previously predicted nodal lines in these kagome compounds. In Co3Sn2S2, we also trace how electronic band topology is varied by changing the orientation of the magnetization. F.Schilberth et al., PRB 106,144404; 107,214441
Date: Thu, 14.03.2024
Time: 15:00
Duration: 45 min
Location:Freihaus DB gelb 09 Stock, https://tuw-maps.tuwien.ac.at/?q=DB09E23
Contact:Andrei Pimenov

Memory attacks in network nonlocality and self-testing
Speaker:Mirjam Weilenmann (University of Geneva)
Abstract:Networks of quantum systems give us new approaches for understanding the foundations of quantum theory and for developing new applications for quantum technology. I will introduce this subject as a generalization of the famous Bell scenario and introduce recent research trends, including self-testing as well as the role of memory attacks for cryptography. I will then present a recent work, where we study what can or cannot be certified in communication scenarios in such networks where the assumption of independence and identical distribution (iid) between experimental rounds fails. In this respect, we prove that membership tests for non-convex sets of correlations cannot be formulated in the non-iid regime. Similarly, it is impossible to self-test non-extreme quantum operations, such as mixed states, or noisy quantum measurements, unless one allows more than a single use thereof within
Date: Fri, 15.03.2024
Time: 10:00
Duration: 45 min
Location:Helmut Rauch Hörsaal ATI
Contact:Nicolai Friis

The ADM decomposition 'done right'
Speaker:Robert Beig (U of Vienna)
Abstract:I review the 3+1-decomposition of GR or other field theories done in such a way that the time leaves need not form a foliation, i.e. where the lapse function can become zero or even change sign. I make remarks on local existence as well as on the relation with the 'hypersurface deformation algebra' put forward by Teitelboim, Kuchar and others.
Date: Fri, 15.03.2024
Time: 14:30
Duration: 60 min
Location:Library, Waehringer St. 17
Contact:P. Chrusciel