Gabriel Sánchez-Pérez, University of Salamanca
Understanding null hypersurfaces is fundamental to general relativity, as several key concepts in the theory are modeled by them, such as black hole event horizons, Cauchy horizons, and the null infinity of asymptotically flat spacetimes. In this talk, I will present a formalism capable of treating null hypersurfaces in an intrinsic, abstract manner. I will highlight several of its key applications, namely the formulation of the characteristic Cauchy problem in geometric terms, the existence and uniqueness properties of spacetimes near a single null hypersurface (with particular focus on Killing horizons), and the asymptotic behavior of spacetimes near
their null infinity. This talk is based on Chapters 2, 3, 5 and 6 of arXiv:2604.19668.
