Laval nozzle as an acoustic analogue of a massive field

TL;DR

This paper demonstrates how to design a Laval nozzle that acts as an acoustic analogue of a massive scalar field around a Schwarzschild black hole, enabling laboratory observation of quasinormal modes.

Contribution

It introduces a method to shape Laval nozzles so that acoustic perturbations mimic the wave equation of a massive scalar field in black hole spacetime.

Findings

Designed a Laval nozzle matching the wave equation of a massive scalar field

Proposed laboratory setup to observe black hole quasinormal ringing

Identified conditions for long-living oscillations in the spectrum

Abstract

We study a gas flow in the Laval nozzle, which is a convergent-divergent tube that has a sonic point in its throat. We show how to obtain the appropriate form of the tube, so that the acoustic perturbations of the gas flow in it satisfy any given wavelike equation. With the help of the proposed method we find the Laval nozzle, which is an acoustic analogue of the massive scalar field in the background of the Schwarzschild black hole. This gives us a possibility to observe in a laboratory the quasinormal ringing of the massive scalar field, which, for special set of the parameters, can have infinitely long-living oscillations in its spectrum.