"Waveforms" at the Horizon

TL;DR

This paper analyzes how a light particle scattering off a Schwarzschild black hole induces perturbations and calculates the resulting energy and angular momentum fluxes entering the black hole, providing new post-Minkowskian results.

Contribution

It derives the horizon fields and fluxes for gravitational, electromagnetic, and scalar radiation in the PM regime, including a novel angular momentum absorption result.

Findings

Agreement with recent energy absorption computations

New PM result for angular momentum absorption

Quantitative description of horizon perturbations in scattering events

Abstract

We study perturbations induced by a light particle scattering off a Schwarzschild black hole. Exploiting recent results for the wave propagation in this geometry, we derive the fields that this process induces on the horizon to leading order in the post-Minkowskian (PM) regime, when the light probe is far from the black hole. We then use these results to calculate the fluxes of energy and angular momentum that enter the black hole. We consider the effects due to gravitational, electromagnetic and scalar radiation, finding agreement with recent computations of the absorbed energy, while the absorbed angular momentum provides a new PM result.