The Rotating Black Hole Interior: Insights from Gravitational Collapse in (2+1)D

We address a hole in the space of existing toy models for the astrophysical black hole (BH) interior by simulating the gravitational collapse of \textit{rotating} matter in (2+1)D classical general relativity. We compare and contrast our time-dependent numerical solution to the stationary analytic solution due to Ba\~nados, Teitelboim, and Zanelli (BTZ), as well as to the celebrated Kerr solution. We focus on three features in the dynamical case: the singularity structure, the regularity of the Cauchy horizon, and the geodesic-focusing effect first described by Marolf \& Ori. We observe the latter effect for the first time in a BH formed from gravitational collapse. We also find that curvature singularities form at the origin and Cauchy horizon for low spin, but disappear entirely for sufficiently high spins, signaling a violation of the $C^0$ and $C^2$ formulations of the strong cosmic censorship conjecture.