Greybody factors for topological massless black holes

TL;DR

This paper analyzes greybody factors for topological massless black holes, revealing that certain modes contribute to absorption at zero frequency and confirming the conservation relation between reflection and transmission coefficients.

Contribution

It provides new insights into the low-energy absorption cross section for topological black holes, highlighting the role of specific modes and the validity of flux conservation.

Findings

Modes with lowest angular momentum contribute to zero-frequency absorption.

The sum of reflection and transmission coefficients equals one for these black holes.

Certain modes contribute to the absorption cross section at zero frequency.

Abstract

We study the reflection coefficient, the transmission coefficient and the greybody factors for black holes with topologically non trivial transverse sections in 4 and d-dimensions, in the limit of low energy. Considering a massive scalar field in a topological massless black hole background, which is non minimally coupled to the curvature and assuming the horizon geometry with a negative constant curvature. Mainly, we show that there is range of modes which contribute to the absorption cross section in the zero-frequency limit, at difference of the result existing in the literature. Where, the mode with lowest angular momentum contribute to the absorption cross section. Also we show that the condition that the sum of the reflection coefficient and the transmission coefficient is equal to one is always satisfied for these kind of black holes.