Dark matter annihilation in the gravitational field of a black hole

TL;DR

This paper models dark matter annihilation near black holes, revealing increased density and high-energy effects that influence gamma-ray signals and have potential observational implications.

Contribution

It provides an exact distribution function for infalling dark matter particles and analyzes the impact on gamma-ray flux and spectra near black holes.

Findings

Dark matter density increases significantly near black holes.

Particle collision energies become very high close to black holes.

Altered annihilation cross-sections affect gamma-ray signals.

Abstract

In this paper we consider dark matter particle annihilation in the gravitational field of black holes. We obtain exact distribution function of the infalling dark matter particles, and compute the resulting flux and spectra of gamma rays coming from the objects. It is shown that the dark matter density significantly increases near a black hole. Particle collision energy becomes very high affecting relative cross-sections of various annihilation channels. We also discuss possible experimental consequences of these effects.