Soft Black Hole Absorption Rates as Conservation Laws

TL;DR

This paper demonstrates that the absorption rates of soft electromagnetic radiation by black holes are determined by conservation laws, linking them to large gauge symmetries and Ward identities, and extends previous analytic results.

Contribution

It establishes a connection between black hole absorption rates and conservation laws, providing a new interpretation via large gauge transformations and Ward identities.

Findings

Absorption rates are fixed by conservation of energy and gauge symmetries.

Re-derivation and extension of previous results for scalar and photon absorption.

Linking absorption phenomena to fundamental symmetry principles.

Abstract

The absorption rate of low-energy, or soft, electromagnetic radiation by spherically symmetric black holes in arbitrary dimensions is shown to be fixed by conservation of energy and large gauge transformations. We interpret this result as the explicit realization of the Hawking-Perry-Strominger Ward identity for large gauge transformations in the background of a non-evaporating black hole. Along the way we rederive and extend previous analytic results regarding the absorption rate for the minimal scalar and the photon.