Perturbations and absorption cross-section of infinite-radius black rings

TL;DR

This paper investigates scalar field perturbations on black ring geometries, demonstrating stability and analyzing absorption cross-sections in the infinite-radius limit, revealing relationships to the horizon area.

Contribution

It provides the first analysis of scalar perturbations and absorption cross-sections for black rings in the infinite-radius limit, including stability results.

Findings

Both geometries are stable against scalar perturbations.

Absorption cross-section equals horizon area in supersymmetric case.

Proportional absorption cross-section in non-supersymmetric case.

Abstract

We study scalar field perturbations on the background of non-supersymmetric black rings and of supersymmetric black rings. In the infinite-radius limit of these geometries, we are able to separate the wave equation, and to study wave phenomena in its vicinities. In this limit, we show that (i) both geometries are stable against scalar field perturbations, (ii) the absorption cross-section for scalar fields is equal to the area of the event horizon in the supersymmetric case, and proportional to it in the non-supersymmetric situation.