Black hole lasers in Bose-Einstein condensates

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.

iopams, 37 pages, 14 figures, 1 table; for associated gif animations, see http://people.sissa.it/~finazzi/bec_bhlasers/movies/ or http://iopscience.iop.org/1367-2630/12/9/095015/media. Published on New. J. Phys. (http://iopscience.iop.org/1367-2630/12/9/095015/). V2: few new comments, modified figures