Scattering of scalar particles by a black hole

TL;DR

This paper calculates how scalar particles are absorbed by a Schwarzschild black hole, revealing that low-energy absorption vanishes due to horizon reflection effects, a property likely true for particles of any spin.

Contribution

It introduces the impact of horizon reflection on absorption cross sections, extending understanding beyond the well-known greybody factor effects.

Findings

Absorption cross section diminishes at low energies due to horizon reflection.

The cross section approaches zero in the infrared limit for scalar particles.

The effect is argued to be general for particles of arbitrary spin.

Abstract

The absorption cross section for scalar particle impact on a Schwarzschild black hole is found. The process is dominated by two physical phenomena. One of them is the well-known greybody factor that arises from the energy-dependent potential barrier outside the horizon that filters the incoming and outgoing waves. The other is related to the reflection of particles on the horizon (Kuchiev 2003). This latter effect strongly diminishes the cross section for low energies, forcing it to vanish in the infrared limit. It is argued that this is a general property, the absorption cross section vanishes in the infrared limit for scattering of particles of arbitrary spin.