Quasistationary solutions of self-gravitating scalar fields around collapsing stars

TL;DR

This paper demonstrates through numerical simulations that scalar fields can form long-lived, quasistationary configurations around black holes resulting from collapsing supermassive stars, supporting their role as dark matter candidates.

Contribution

The study provides the first numerical evidence that scalar fields can survive stellar collapse and form quasistationary states around black holes.

Findings

Scalar fields form long-lived configurations post-collapse.

Quasistationary scalar field states persist around black holes.

Collapse of supermassive stars does not destroy scalar field structures.

Abstract

Recent work has shown that scalar fields around black holes can form long-lived, quasistationary configurations surviving for cosmological timescales. With this requirement, scalar fields cannot be discarded as viable candidates for dark matter halo models in galaxies around central supermassive black holes (SMBH). One hypothesis for the formation of most SMBHs at high redshift is the gravitational collapse of supermassive stars (SMS) with masses of $\sim10^5 \rm {M_{\odot}}$. Therefore, a constraint for the existence of quasi-bound states of scalar fields is their survival to such dynamic events. To answer this question we present in this paper the results of a series of numerical relativity simulations of gravitationally collapsing, spherically symmetric stars surrounded by self-gravitating scalar fields. We use an ideal fluid equation of state with adiabatic index $\Gamma=4/3$ which is adequate to simulate radiation-dominated isentropic SMSs. Our results confirm the existence of oscillating, long-lived, self-gravitating scalar field configurations around non-rotating black holes after the collapse of the stars.