Quantum Criticality in Black Hole Scattering

Black hole perturbation theory captures a few important effects in the dynamics of binary mergers, such as tidal deformations and the decay of ringdown modes. It also describes the physics of the photon ring. However, extracting qualitative results that lead to robust predictions within this theory has remained a long-standing challenge.

Motivated by the remarkable experimental progress of the last decade, and the corresponding need for qualitative theoretical predictions, I will describe a new critical phenomenon emerging in the theory of perturbations around Kerr black holes. At zero black hole temperature the theory exhibits a critical point, which in turn governs a broad finite-temperature regime dominated by critical perturbations. Much like in quantum many-body systems, the physics in this regime is described exclusively by a set of critical exponents. This universality leads to robust and distinctive predictions that are unique to the Kerr geometry.