Bounding the Greybody Factors for Non-rotating Black Holes

TL;DR

This paper derives bounds on the greybody factors for non-rotating black holes, showing how charge, extra dimensions, and cosmological constant influence Hawking radiation emission.

Contribution

It introduces a transfer matrix formalism to establish bounds on greybody factors for charged and higher-dimensional black holes, highlighting the effects of charge, extra dimensions, and cosmological constant.

Findings

Black hole charge acts as an effective barrier.

Extra dimensions can shield Hawking radiation.

Cosmological constant increases Hawking radiation emission rate.

Abstract

Semiclassical black holes emit radiation called Hawking radiation. Such radiation, as seen by an asymptotic observer far outside the black hole, differs from original radiation near the horizon of the black hole by a redshift factor and the so-called "greybody factor". In this paper, we concentrate on the greybody factor-various bounds for the greybody factors of non-rotating black holes are obtained, concentrating on charged Reissner-Nordstrom and Reissner-Nordstrom-de Sitter black holes. These bounds can be derived by using a 2x2 transfer matrix formalism. It is found that the charges of black holes act as efficient barriers. Furthermore, adding extra dimensions to spacetime can shield Hawking radiation. Finally, the cosmological constant can increase the emission rate of Hawking radiation.