Bulk emission of scalars by a rotating black hole

TL;DR

This paper analyzes scalar Hawking radiation emitted into the bulk by higher-dimensional rotating black holes, revealing that bulk emission is generally smaller than brane emission and is influenced by black hole angular momentum and dimensionality.

Contribution

It provides detailed numerical calculations of bulk scalar emission, including angular eigenvalues, transmission factors, and emission ratios, for rotating higher-dimensional black holes.

Findings

Bulk emission is enhanced by black hole angular momentum.

Superradiance effects are observed in the emission spectra.

Bulk emission remains significantly smaller than brane emission across scenarios.

Abstract

We study in detail the scalar-field Hawking radiation emitted into the bulk by a higher-dimensional, rotating black hole. We numerically compute the angular eigenvalues, and solve the radial equation of motion in order to find transmission factors. The latter are found to be enhanced by the angular momentum of the black hole, and to exhibit the well-known effect of superradiance. The corresponding power spectra for scalar fields show an enhancement with the number of dimensions, as in the non-rotating case. We compute the total mass loss rate of the black hole for a variety of black-hole angular momenta and bulk dimensions, and find that, in all cases, the bulk emission remains significantly smaller than the brane emission. The angular-momentum loss rate is also computed and found to have a smaller value in the bulk than on the brane. We present accurate bulk-to-brane emission ratios for a range of scenarios.