Radiation reaction for spinning black-hole scattering

TL;DR

This paper calculates the effects of radiation reaction in spinning black-hole scattering at two loops, providing new insights into energy, angular momentum loss, and deflection angles for various spins using amplitude methods.

Contribution

It introduces a novel amplitude-based approach to compute radiation reaction effects for spinning black holes at two loops, including spin orientations.

Findings

Agreement with supersymmetric worldline results for spin one

Derived deflection angles and angular momentum loss for arbitrary spins

Computed energy spectrum in the zero frequency limit

Abstract

Starting from the leading soft term of the 5-point amplitude, involving a graviton and two Kerr black holes, that factorises into the product of the elastic amplitude without the graviton and the leading soft factor, we compute the infrared divergent contribution to the imaginary part of the two-loop eikonal. Then, using analyticity and crossing symmetry, we determine the radiative contribution to the real part of the two-loop eikonal and from it the radiative part of the deflection angle for spins aligned to the orbital angular momentum, the loss of angular momentum and the zero frequency limit of the energy spectrum for any spin and for any spin orientation. For spin one we find perfect agreement with recent results obtained with the supersymmetric worldline formalism.