Schwarzschild black holes can wear scalar wigs

TL;DR

This paper demonstrates that certain scalar field configurations around Schwarzschild black holes can persist for extremely long times, potentially explaining phenomena like dark matter halos and axion-like particles around black holes.

Contribution

It shows the existence of long-lived scalar field configurations around Schwarzschild black holes, applicable to dark matter and primordial black holes, with generic initial data evolving into these states.

Findings

Scalar fields can form long-lived configurations around black holes.

Ultra-light scalar dark matter can survive cosmological times.

Results are robust for a wide range of initial conditions.

Abstract

We study the evolution of a massive scalar field surrounding a Schwarzschild black hole and find configurations that can survive for arbitrarily long times, provided the black hole or the scalar field mass is small enough. In particular, both ultra-light scalar field dark matter around supermassive black holes and axion-like scalar fields around primordial black holes can survive for cosmological times. Moreover, these results are quite generic, in the sense that fairly arbitrary initial data evolves, at late times, as a combination of those long-lived configurations.