Matter Accretion by Brane-World Black Holes

TL;DR

This paper investigates matter accretion onto brane-world black holes using relativistic hydrodynamics, deriving profiles of physical parameters, and suggests astrophysical observations could distinguish brane-world models from standard black holes.

Contribution

It develops a general formalism for relativistic accretion onto static, spherically symmetric brane-world black holes, including velocity, temperature, and density profiles.

Findings

Flow transitions to supersonic speeds near black holes

Profiles of gas velocity, temperature, and density are obtained

Accretion properties vary across different brane-world black hole models

Abstract

The brane-world description of our universe entails a large extra dimension and a fundamental scale of gravity that might be lower by several orders of magnitude compared to the Planck scale. An interesting consequence of the brane-world scenario is in the nature of spherically symmetric vacuum solutions to the brane gravitational field equations, with properties quite distinct as compared to the standard black-hole solutions of general relativity. We consider the spherically symmetric accretion of matter onto brane-world black holes in terms of relativistic hydrodynamics by assuming that the inflowing gas obeys a polytropic equation of state. As a first step in this study, we consider the accretion process in an arbitrary static, spherically symmetric space-time, and show that the relativistic equations require a transition to a supersonic flow in the solution. The velocity, temperature, and density profiles are obtained for the case of the polytropic equation of state. We apply the general formalism to the study of the accretion properties of several classes of brane-world black holes, and we obtain the distribution of the main physical parameters of the gas. The astrophysical determination of these physical quantities could discriminate, at least in principle, between the different brane-world models, and place some constraints on the existence of the extra dimensions.