Joint Theory Seminar: Henrik Johansson

Title: Scattering of Kerr black holes from higher-spin QFT

Abstract: Over the past few years it has become increasingly clear that quantum scattering amplitudes can be used to gain insights into the dynamics of Kerr black holes. A simple infinite family of three-point amplitudes, describing the primary gravitational interaction of a black hole with quantum spin s, is by now well established. However, the corresponding Compton four-point tree-level amplitudes are only know up to s=2 with certainty, and beyond s>2 there exists conjectures. Compton amplitudes are needed for post-Minkowskian scattering and post-Newtonian calculations of inspiraling black-hole systems. In this talk, I will discuss the observation that the established Kerr three-point amplitudes can be uniquely predicted from the principle of gauge symmetry. In particular, I will consider a family of EFTs with Stuckelberg higher-spin fields that describe the Kerr black holes. The EFTs enjoy massive higher-spin gauge symmetry, which ensures the correct 2s+1 degrees of freedom. In parallel, I will consider a chiral higher-spin QFT that automatically has the correct DoFs, at the expense of non-manifest parity, and turns out to be surprisingly efficient for Compton amplitude computations. Finally, I will present an infinite spin-s family of quantum Compton amplitudes that matches the known rational terms from explicit GR calculations in Kerr background.