Black hole lasers in Bose Einstein condensates

Renaud Parentani

Being the end of the gravitation evolution, black holes should be stable objects. However, under specific conditions, they are subject to various types of instabilities. Some of them are also found when considering analogue black holes, and a neat example is provided by the "black hole laser" in Bose Einstein condensates. When the condensate crosses twice the speed of sound, the phonon spectrum possesses a discrete and finite set of complex frequency modes. In classical terms, these encode a dynamical instability. At the quantum level, they engender a laser effect. In terms of the gravitational analogy, this effect can be conceived as a self-amplified Hawking radiation. This is verified by comparing the phonon flux at early time with the standard black hole radiation.