Title
The intrinsic geometry of extremal horizons
Abstract
We study the geometry of extremal horizons in a spacetime, which arise most prominently as the event horizons of extremal black holes in General Relativity. The Einstein equations induce a system of elliptic PDEs on a compact (Riemannian) cross-section of the horizon that can be analysed without reference to the exterior spacetime.
Building on work by Dunajski and Lucietti, we prove a rigidity theorem for extremal horizons in a spacetime of arbitrary dimension and with general matter content: any compact cross-section of a rotating extremal horizon must admit a Killing field. Restricting to four-dimensional Einstein-Maxwell theory, we discuss how this result completes the classification of extremal horizons. In particular, any rotating horizon must have spherical cross-sections and arises from an extremal Kerr-Newman spacetime.
Please note that the seminar will take place in person in room 140 of Huxley Building.