Vorträge in der Woche 29.06.2026 bis 05.07.2026
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Mittwoch, 01.07.2026: On surfaces of constant spacetime mean curvature in Minkowski spacetime
Prof. Dr. Carla Cederbaum (Universität Tübingen))
Abstract: Surfaces of constant spacetime (or co-dimension $2$) mean curvature (STCMC) have been shown to be abundant in the asymptotic end(s) of any asymptotically Minkowskian spacetime of non-vanishing mass (C.—Sakovich ’21). It has since been an open question how many STCMC-surfaces there are in Minkowski spacetime. We will explain why there are in fact many STCMC-surfaces in Minkowski spacetime. Our analysis is based on a characterization of local STCMC-foliations in relativistic initial data sets by Metzger—Pe\~nuela which in turn goes back to a local CMC-foliation result in Riemannian manifolds by Ye. We will also briefly touch on the corresponding Riemannian result by Yau who argues for rigidity of co-dimension $2$ constant mean curvature (CMC) surfaces in Euclidean $4$-space. In particular, we will indicate how the stark difference between the Euclidean and Minkowskian results can be resolved.
| Uhrzeit: | 15:30 |
| Ort: | C2A17 |
| Gruppe: | Oberseminar Geometrische Analysis, Differentialgeometrie und Relativitätstheorie |
| Einladender: | Carla Cederbaum |
Donnerstag, 02.07.2026: On a conjecture by Horowitz and Tod
Salvatore Vultaggio (Universität Tübingen)
In 1982, Tod and Horowitz proposed a “unified framework for discussing energy in General Relativity”, which allowed to simultaneously treat the otherwise seemingly incompatible null and space-like asymptotic regimes. The final steppingstone in the paper is a conjecture: our effort is being concentrated on a formal analysis of this conjecture, making use of the Conformal Methods pioneered by Friedrich.
| Uhrzeit: | 14:00 |
| Ort: | C4H33 and virtual via zoom, for zoom link please contact Abir Seghirate |
| Gruppe: | Oberseminar Geometrische Analysis, Differentialgeometrie und Relativitätstheorie |
| Einladender: | Carla Cederbaum, Gerhard Huisken, zusammen mit Jan Metzger (Potsdam) |
Donnerstag, 02.07.2026: Topological phases of non-interacting systems: A general approach based on states
Prof. Giuseppe de Nittis (Pontificia Universidad Católica de Chile)
In this work we provide a classification scheme for topological phases of certain systems whose observable algebra is described by certain (trivial) C*-bundles. The classification is based on the study of the homotopy classes of configurations, which are maps from a quantum parameter space to the space of pure states of a reference fiber C*-algebra. Both the quantum parameter space and the fiber algebra are naturally associated with the observable algebra. A list of various examples described in the last part shows that the common classification scheme of non-interacting topological insulators of type A is recovered inside this new formalism.
| Uhrzeit: | 14:30 |
| Ort: | C3N14 |
| Gruppe: | Oberseminar Mathematical Physics |
| Einladender: | Keppeler, Lemm, Pickl, Teufel, Tumulka |
Donnerstag, 02.07.2026: Rapid mixing in long-range Lindbladians and static properties in their fixed points
Angela Capel Cuevas (Cambridge/Tübingen)
The classification of mixed-state phases requires criteria beyond two-point correlation functions, such as the decay of the mutual information (MI) and the conditional mutual information(CMI), with the latter encapsulated in the notion of Markov length. In this talk, we show how such static properties of the fixed point of a Lindbladian follow from natural dynamical features of its generator: rapid mixing and frustration-freeness. We focus on systems with long-range interactions, and prove i)that local Lindbladians satisfying (global) rapid mixing and frustration-freeness have fixed-points whose CMI decays with the shielding distance, and ii) that (local) rapid mixing together with primitivity and regularity implies global decay of MI. For long-range interactions both quantities decay polynomially rather than exponentially, in contrast to the finite- and short-range regimes where exponential decay (a finite Markov length) is expected within a phase. We further show that Gibbs states of long-range, non-commuting Hamiltonians satisfy a local Markov property at any temperature.
| Uhrzeit: | 16:00 |
| Ort: | C3N14 |
| Gruppe: | Oberseminar Mathematical Physics |
| Einladender: | Keppeler, Lemm, Pickl, Teufel, Tumulka |