My research interests are black holes, and more generally the theory of General Relativity.

My first line of research involved the study of non-smooth horizons. The event horizons of dynamical black holes generically exhibit non-smooth features, including creases and caustics. With collaborators, I studied these features, provided a classification of such features in 4 dimensions, and described their properties. I explored the merger of two Kerr black holes and showed that these features are indeed present, and have the correct mathematical properties. I also showed that these features exist on dynamical cosmological horizons.

My current research relates to the third law of black hole mechanics. A counterexample was recently found in spherical symmetry, but the rotating case remains open. My goal is to find a spacetime in which an extremal rotating black hole is formed in finite time, or to find evidence that such a construction is not possible.

Email: mjhg2@cam.ac.uk