Instability of the superfluid flow as black-hole lasing effect

TL;DR

This paper demonstrates that the decay of one-dimensional superfluid flow through a barrier is caused by a black-hole lasing effect, where resonant modes in an effective cavity lead to dynamical instability, with critical velocity determined by horizon configuration.

Contribution

It introduces the black-hole lasing effect as the mechanism behind superfluid flow instability and provides an analytical expression for the critical velocity based on horizon configuration.

Findings

Critical velocity is analytically determined by horizon configuration.

Instability arises from modes resonating in an effective cavity formed by horizons.

Broad barriers recover Hawking-like radiation spectrum and Landau instability.

Abstract

We show that the instability leading to the decay of the one-dimensional superfluid flow through a penetrable barrier are due to the black-hole lasing effect. This dynamical instability is triggered by modes resonating in an effective cavity formed by two horizons enclosing the barrier. The location of the horizons is set by $v(x)=c(x)$, with $v(x),c(x)$ being the local fluid velocity and sound speed, respectively. We compute the critical velocity analytically and show that it is univocally determined by the horizons configuration. In the limit of broad barriers, the continuous spectrum at the origin of the Hawking-like radiation and of the Landau energetic instability is recovered.