Assessing the stability of ultracompact spinning boson stars with nonlinear evolutions

TL;DR

This study uses advanced numerical relativity simulations to investigate the stability of ultracompact spinning boson stars with light rings, finding no signs of instability over long timescales despite various perturbations.

Contribution

It provides the first comprehensive nonlinear stability analysis of ultracompact spinning boson stars with light rings using multiple formulations of Einstein's equations.

Findings

No evidence of instability over timescales of tμ ~ 10^4

Perturbations decay slowly, indicating stability

Results suggest ultracompact spinning boson stars are stable under various conditions

Abstract

We reinvestigate the stability properties of ultracompact spinning boson stars with a stable light ring using fully nonlinear 3+1 and 2+1 numerical relativity simulations and two different formulations of the Einstein equations. We find no evidence of an instability on timescales of $t \mu \sim 10^4$ (in units of the scalar mass), when allowing the star to be perturbed either solely by discretization error or by imposing various types of perturbations to our initial data. We find that the initially imposed perturbations exhibit slow decay, even for magnitudes just below the order where immediate collapse is induced.