Perturbing the vortex: quasinormal and quasibound spectra of rotating acoustic geometries

TL;DR

This paper introduces a novel acoustic geometry model simulating rotating black hole features in laboratory fluids, analyzing quasinormal and quasibound spectra to explore strong-field gravity phenomena.

Contribution

It presents a new effective geometry for rotating acoustic black holes, including azimuthal circulation, and computes their quasinormal and quasibound spectra semi-analytically and exactly.

Findings

Spectra match co-rotating and counter-rotating surface waves.

Behavior aligns with recent superfluid experiments.

Provides a quantum-field-theory simulator for rotating spacetimes.

Abstract

Strong-field gravity simulators are laboratory experiments that can investigate a wide range of both classical and quantum phenomena occurring in nature. In this work, we introduce an effective geometry that captures most of the characteristics of the strong-field regime of astrophysical, rotating black holes. This geometry can represent a vortex made from a variety of fluid and superfluid profiles with zero viscosity, making it a promising finite-temperature quantum-field-theory simulator for rotating curved spacetimes. Our geometry includes not only the typical radial flow which gives rise to an acoustic horizon, but also azimuthal circulation of the fluid. We compute the quasinormal modes, semi-analytically, and the exact quasibound states of acoustic excitations interacting with this effective geometry. The resulting spectra can be identified for both co-rotating and counter-rotating surface acoustic waves. In particular, the behavior of our acoustic geometry with circulation aligns with the phenomenology observed in recent experiments that include superfluids.