From scalar clouds around evaporating black holes to boson star

TL;DR

This paper investigates how scalar clouds around evaporating black holes can evolve into boson stars, revealing a new formation mechanism that could enhance the detectability of bosonic dark matter.

Contribution

It introduces the first simulation of scalar cloud evolution around evaporating black holes, demonstrating a novel pathway for boson star formation during black hole evaporation.

Findings

Scalar clouds can survive as boson stars if black holes evaporate slowly.

Black hole evaporation can produce micro-boson stars with high occupation numbers.

This mechanism may improve prospects for detecting bosonic dark matter.

Abstract

We study, for the first time, the evolution of a scalar cloud bound to an evaporating black hole. Our simulations of the associated Schr\"odinger-Poisson system for non-relativistic and spherically symmetric clouds reveal that a scalar cloud may (partially) survive as a self-gravitating boson star if the black hole evaporates adiabatically until its mass becomes less than one half of the cloud's mass. This yields a novel mechanism for boson star formation and shows that, as previously conjectured, bosonic dark matter production by light primordial black holes may result in micro-boson stars with very large occupation numbers, greatly enhancing their potential detectability even for very weakly interacting dark matter particles.