Stimulated radiation from superradiant scalar cloud in scalar-tensor theory

TL;DR

This paper explores how superradiant scalar clouds around Kerr black holes in scalar-tensor theories can produce detectable electromagnetic signals through stimulated decay, offering a new observational signature for fundamental scalars.

Contribution

It demonstrates that stimulated decay of scalar clouds in scalar-tensor theories can generate observable signals, highlighting the role of matter distribution and scalar-matter coupling in this process.

Findings

Stimulated decay produces detectable electromagnetic signals.

Growth of scalar clouds depends on surrounding matter distribution.

Stimulated emission can distinguish fundamental scalars from other bosons.

Abstract

Scalar-tensor theories predict fundamental scalar fields of considerable interest in astrophysics and cosmology. We investigate the superradiant instability of scalar clouds around Kerr black holes, showing that stimulated decay generates detectable electromagnetic signals. The growth of the superradiant scalar cloud differs from that of other bosonic fields and depends sensitively on the matter distribution surrounding the black hole, which originates from the scalar-matter coupling realized by the chameleon mechanism in modified gravity theories. In non-uniform matter distributions, stimulated emission from scalar clouds offers an observational signature that distinguishes fundamental scalars from other light bosonic fields.