Black holes in asymptotic safety with higher derivatives: accretion and stability analysis

TL;DR

This paper investigates steady accretion onto a quantum-corrected black hole in asymptotic safety, analyzing different fluids and stability, revealing new physical solutions and quantum effects on stability.

Contribution

It demonstrates the existence of physical accretion solutions for ultra-relativistic fluids in asymptotic safety, correcting previous claims, and studies quantum effects on accretion stability.

Findings

Existence of subsonic, supersonic, and transonic accretion solutions in AS.

Quantum effects can either stabilize or destabilize accretion.

Accretion solutions differ from classical GR predictions.

Abstract

We review the issue of steady spherically symmetric accretion onto a renormalization group improved Schwarzschild space-time which is solution to an asymptotically safe theory (AS) containing high-derivative terms. We use a Hamiltonian dynamical system approach for the analysis of the accretion of four types of isothermal test fluids: ultra-stiff fluid, ultra-relativistic fluid, radiation fluid, and sub-relativistic fluid. An important outcome of our study is that, contrary to what claimed in a recent work, there exist physical solutions for the accretion of an ultra-relativistic fluid in AS which include subsonic, supersonic and transonic regimes. We also study quantum corrections to the known stability of the accretion in general relativity (GR). To this end we use a perturbative procedure based on the continuity equation with the mass accretion rate being the perturbed quantity. Two classes of perturbations are studied: standing waves and travelling waves. We find that quantum gravity effects either enhance or diminish the stability of the accretion depending on the type of test fluid and depending on the radial distance to the central object.