Acoustic black-hole bombs and scalar clouds in a photon-fluid model

TL;DR

This paper demonstrates that a rotating photon-fluid model can exhibit phenomena analogous to black-hole superradiant instabilities and scalar clouds, providing a potential platform for analogue gravity experiments.

Contribution

It shows that vortex flows in a photon-fluid can produce superradiant instabilities and stationary scalar clouds, mimicking astrophysical black-hole phenomena.

Findings

Superradiant phonon instabilities in photon-fluids

Existence of stationary modes synchronized with the horizon

Photon-fluid system as an analogue for black-hole scalar clouds

Abstract

Massive bosonic fields in the background of a Kerr black hole can either trigger superradiant instabilities (black-hole bombs) or form equilibrium configurations corresponding to pure bound states, known as stationary scalar clouds. Here, similar phenomena are shown to emerge in the fluctuation dynamics of a rotating photon-fluid model. In the presence of suitable vortex flows, the density fluctuations are governed by the massive Klein-Gordon equation on a (2+1) curved spacetime, possessing an ergoregion and an event horizon. We report on superradiant instabilities originating from quasi-bound phonon states trapped by the vortex background and, remarkably, on the existence of stationary modes in synchronous rotation with the horizon. These represent the acoustic counterpart of astrophysical scalar clouds. Our system offers a promising platform for analogue gravity experiments on superradiant instabilities of massive bosons and black-hole-field equilibrium configurations.