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Calendar of Physics Talks Vienna
| 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 |
| 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 |
| 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 |
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