Greybody factors for rotating black holes in four dimensions

TL;DR

This paper derives the wave equation for scalar fields around rotating four-dimensional black holes, calculates greybody factors for Hawking radiation, and interprets the emission spectrum via an effective string theory approach.

Contribution

It provides a detailed analysis of greybody factors for rotating 4D black holes, extending previous 5D results, and offers a string theory interpretation of Hawking radiation spectra.

Findings

Greybody factors calculated for non-extremal black holes.

Emission spectrum analyzed for large partial wave numbers.

Effective string theory description of Hawking radiation spectrum.

Abstract

We present the wave equation for a minimally coupled scalar field in the background of a rotating four-dimensional black hole that is parametrized by its mass, angular momentum, and four independent U(1) charges. The near horizon structure is identical to the five-dimensional case, and suggestive of an underlying description in string theory that is valid in the general non-extremal case. We calculate the greybody factors for the Hawking radiation. For sufficiently large partial wave number the emission spectrum can be calculated for general non-extremal black holes and any particle energy. We interpret this spectrum in terms of a multi-body process in an effective string theory.