Black hole lasers in Bose-Einstein condensates

TL;DR

This paper explores how Bose-Einstein condensates with supersonic flows can exhibit laser-like instabilities analogous to black hole horizons, leading to self-amplified Hawking radiation signatures.

Contribution

It demonstrates the existence of a laser effect in Bose-Einstein condensates with black hole and white hole horizon analogs, including numerical computation of complex frequencies.

Findings

Identification of discrete complex frequency modes causing laser effect

Numerical computation of density-density correlations showing specific patterns

Evidence of self-amplified Hawking radiation in the system

Abstract

We consider elongated condensates that cross twice the speed of sound. In the absence of periodic boundary conditions, the phonon spectrum possesses a discrete and finite set of complex frequency modes that induce a laser effect. This effect constitutes a dynamical instability and is due to the fact that the supersonic region acts as a resonant cavity. We numerically compute the complex frequencies and density-density correlation function. We obtain patterns with very specific signatures. In terms of the gravitational analogy, the flows we consider correspond to a pair of black hole and white hole horizons, and the laser effect can be conceived as a self-amplified Hawking radiation. This is verified by comparing the outgoing flux at early time with the standard black hole radiation.