8 May 2025 (note the unusual day!)
3:40pm CEST
MARC MARS
(University of Salamanca, Spain)
Title: Null geometry and applications to existence of spacetimes
Abstract: Non-null hypersurfaces can be easily viewed as geometric objects detached from the spacetime where they are embedded. This process of “detachment” is more complicated in the case of null hypersurfaces. In this talk I will introduce the notion of “null manifold”, together with related concepts such as “ruled null manifold” or “metric hypersurface data”, as a way to study null hypersurfaces from a fully detached point of view. With this framework at hand, I will then discuss three applications related to existence of spacetimes. Specifically, I will present a detached version of the characteristic initial value problem, a general analysis of transverse expansions across a null hypersurface and an existence and asymptotic uniqueness result of Λ-vacuum spacetimes from data on a (detached) non-degenerate Killing horizon. The three applications are joint work with Gabriel Sánchez Pérez.