Are black holes a serious threat to scalar field dark matter models?

TL;DR

This paper investigates the stability of scalar field configurations around black holes, demonstrating the existence of long-lived quasi-stationary solutions that support scalar fields as dark matter candidates.

Contribution

It provides a detailed analytical and numerical analysis of scalar fields near black holes, showing conditions for long-lived configurations relevant to dark matter models.

Findings

Existence of quasi-stationary scalar field solutions around black holes.

Scalar fields can survive for cosmological time-scales near black holes.

Conditions for stability of scalar fields in Schwarzschild spacetime.

Abstract

Classical scalar fields have been proposed as possible candidates for the dark matter component of the universe. Given the fact that super-massive black holes seem to exist at the center of most galaxies, in order to be a viable candidate for the dark matter halo a scalar field configuration should be stable in the presence of a central black hole, or at least be able to survive for cosmological time-scales. In the present work we consider a scalar field as a test field on a Schwarzschild background, and study under which conditions one can obtain long-lived configurations. We present a detailed study of the Klein-Gordon equation in the Schwarzschild spacetime, both from an analytical and numerical point of view, and show that indeed there exist quasi-stationary solutions that can remain surrounding a black hole for large time-scales.