Black Holes in the Ghost Condensate

TL;DR

This paper explores how ghost condensates interact with black holes, showing they accrete similarly to pressureless dust with negligible rates for large black holes, and discusses implications for dark matter.

Contribution

It demonstrates that ghost condensates behave like geodesic flows and accrete into black holes at negligible rates, even considering higher derivative effects.

Findings

Ghost condensate acts like pressureless dust near black holes.

Accretion rate is negligible for large black holes.

Implications for ghost condensate as dark matter.

Abstract

We investigate how the ghost condensate reacts to black holes immersed in it. A ghost condensate defines a hypersurface-orthogonal congruence of timelike curves, each of which has the tangent vector u^\mu=-g^{\mu\nu}\partial_\nu\phi. It is argued that the ghost condensate in this picture approximately corresponds to a congruence of geodesics. In other words, the ghost condensate accretes into a black hole just like a pressure-less dust. Correspondingly, if the energy density of the ghost condensate at large distance is set to an extremely small value by cosmic expansion then the late-time accretion rate of the ghost condensate should be negligible. The accretion rate remains very small even if effects of higher derivative terms are taken into account, provided that the black hole is sufficiently large. It is also discussed how to reconcile the black hole accretion with the possibility that the ghost condensate might behave like dark matter.