Evolution of a mass-less test scalar field on Boson Stars space-times

TL;DR

This study numerically investigates how a massless scalar field behaves on boson star and black hole backgrounds, revealing oscillatory quasi-normal modes in compact boson stars and suggesting limitations on boson stars mimicking black holes.

Contribution

It introduces a numerical method using conformal compactification to analyze scalar fields on boson star space-times, highlighting the restricted parameter space for black hole mimicking.

Findings

Scalar field exhibits quasi-normal-mode oscillations in compact boson stars

No tail decay observed in the explored parameter space

Results suggest boson stars as black hole mimickers are limited to compact configurations

Abstract

We numerically solve the mass-less test scalar field equation on the space-time background of boson stars and black holes. In order to do so, we use a numerical domain that contains future null infinity. We achieve this construction using a scri-fixing conformal compactification technique based on hyperboloidal constant mean curvature foliations of the space-time and solve the conformally invariant wave equation. We present two results: the scalar field shows oscillations of the quasi- normal-mode type found for black holes only for boson star configurations that are compact, and no signs of tail decay is found in the parameter space we explored. Even though our results do not correspond to the master equation of perturbations of boson star solutions, they indicate that the parameter space of boson stars as black hole mimickers is restricted to compact configurations.