Galileon accretion

TL;DR

This paper investigates the steady-state accretion of galileon fields onto Schwarzschild black holes, analyzing stability, existence of critical flows, and implications for black hole thermodynamics within a cosmological context.

Contribution

It provides a detailed analysis of galileon accretion, identifying conditions for critical flow existence and stability, and explores the impact on black hole thermodynamics.

Findings

Critical flow exists for certain parameters but can be unstable.

Critical flow solutions may not exist for some parameter ranges.

The sound horizon can be inside or outside the Schwarzschild horizon, affecting thermodynamics.

Abstract

We study steady-state spherically symmetric accretion of a galileon field onto a Schwarzschild black hole in the test fluid approximation. The galileon is assumed to undergo a stage of cosmological evolution, thus setting a non-trivial boundary condition at spatial infinity. The critical flow is found for some parameters of the theory. There is a range of parameters when the critical flow exists, but the solution is unstable. It is also shown that for a certain range of parameters the critical flow solution does not exist. Depending on the model the sound horizon of the flow can be either outside or inside of the Schwarzschild horizon. The latter property may make it problematic to embed the galileon theory in the standard black hole thermodynamics.