Acoustic clouds: standing sound waves around a black hole analogue

TL;DR

This paper demonstrates that sound waves in a fluid can form stationary cloud-like structures around rotating acoustic black hole analogues, providing a potential experimental platform to study black hole cloud phenomena.

Contribution

It introduces the concept of acoustic clouds around rotating acoustic black holes and compares them to scalar clouds around Kerr black holes, highlighting their potential for experimental investigation.

Findings

Acoustic clouds form stationary waves around rotating acoustic black holes.

Comparison between acoustic clouds and scalar clouds around Kerr black holes.

Potential for experimental testing of black hole cloud phenomena using analog models.

Abstract

Under certain conditions sound waves in fluids experience an acoustic horizon with analogue properties to those of a black hole event horizon. In particular, a draining bathtub-like model can give rise to a rotating acoustic horizon and hence a rotating black hole (acoustic) analogue. We show that sound waves, when enclosed in a cylindrical cavity, can form stationary waves around such rotating acoustic black holes. These acoustic perturbations display similar properties to the scalar clouds that have been studied around Kerr and Kerr-Newman black holes; thus they are dubbed acoustic clouds. We make the comparison between scalar clouds around Kerr black holes and acoustic clouds around the draining bathtub explicit by studying also the properties of scalar clouds around Kerr black holes enclosed in a cavity. Acoustic clouds suggest the possibility of testing, experimentally, the existence and properties of black hole clouds, using analog models.