Lifetime of scalar cloud formation around a rotating regular black hole

TL;DR

This paper investigates how a regularized rotating black hole with a Minkowski core affects the formation timescale of scalar clouds, finding that the regularization shortens the growth time and enhances detection prospects.

Contribution

It introduces a novel regular black hole model with a Minkowski core and demonstrates its impact on scalar cloud formation timescales, extending understanding of superradiant instabilities.

Findings

Regular black hole model shortens scalar cloud formation time

Shorter timescales improve gravitational wave detection prospects

Regularization parameter does not affect superradiant instability regime

Abstract

Does circumventing the curvature singularity of the Kerr black hole affects the timescale of the scalar cloud formation around it? By definition, the scalar cloud, forms a gravitational atom with hydrogen-like bound states, lying on the threshold of a massive scalar field's superradiant instability regime (time-growing quasi-bound states) and beyond (time-decaying quasi-bound states). By taking a novel type of rotating hollow regular black hole proposed by Simpson and Visser which unlike its standard rivals has an asymptotically Minkowski core, we address this question. The metric has a minimal extension relative to the standard Kerr, originating from a single regularization parameter $\ell$, with length dimension. We show with the inclusion of the regularization length scale $\ell$ into the Kerr spacetime, without affecting the standard superradiant instability regime, the timescale of scalar cloud formation gets shorter. Since the scalar cloud after its formation, via energy dissipation, can play the role of a continuum source for gravitational waves, such a reduction in the instability growth time improves the phenomenological detection prospects of new physics because the shorter the time, the more astrophysically important.