News — English

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