Scattering waveforms for Kerr black holes from the soft expansion

In this thesis, I will study the classical scattering problem of two Kerr black holes in general relativity with novel quantum field theory techniques in the Post-Minkowskian (PM) expansion, generalizing the subleading soft theorem to the case of spinning particles. The leading order term in the soft expansion is uniquely determined by the universal Weinberg pole, but the subleading one depends on the angular momentum of the external particles and receives a new spin corrections for classically spinning black holes. Using this approach, I will compute the gravitational Compton amplitude, both in the quantum and classical theory. I will then compute the tree-level five-point amplitude of two spinning point particles emitting a graviton, using the spinor-helicity formalism combined with the soft expansion. Finally, I will use the KMOC formalism to derive the analytic time-domain waveform for the scattering of two Kerr black holes at leading order in the PM expansion.