Scattering Angles in Kerr Metrics

TL;DR

This paper derives scattering angles for probes in Kerr black hole metrics, using a method that sums all orders in black hole spin, and extends results to spinning probes up to second order in spin, aligning with amplitude-based calculations.

Contribution

It introduces a method that naturally resums all orders in Kerr black hole spin and extends scattering angle calculations to spinning probes up to second order in spin.

Findings

Results agree with amplitude and worldline methods at third Post-Minkowskian order.

Method effectively resums all orders in black hole spin.

Extended calculations to spinning probes up to second order in spin.

Abstract

Scattering angles for probes in Kerr metrics are derived for scattering in the equatorial plane of the black hole. We use a method that naturally resums all orders in the spin of the Kerr black hole, thus facilitating comparisons with scattering-angle computations based on the Post-Minkowskian expansion from scattering amplitudes or worldline calculations. We extend these results to spinning black-hole probes up to and including second order in the probe spin and any order in the Post- Minkowskian expansion, for probe spins aligned with the Kerr spin. When truncating to third Post-Minkowskian order, our results agree with those obtained by amplitude and worldline methods.