SPEAKER: Antonin Coutant (Max Planck Institute for Gravitational Physics)
ABSTRACT: I will discuss the analog process of Hawking radiation in Bose-Einstein condensates. As understood by Unruh, for long wavelengths, phonons perceive the background condensate as a space-time metric. Near an acoustic horizon, the redshift at the heart of the Hawking effect imposes to take into account the micro-structure of the condensate, that is, deviations from the relativistic dispersion relation. I will show how the Hawking process is recovered when scales are well separated. I will explain how it arises from an amplication of short wavelength phonons being converted to long wavelength ones. In the presence of two horizons, the Hawking effect is drastically altered. The second horizon provides a "mirror", which feed back the black hole with its own radiation. This results in an instability, called "black hole laser", that have recently been detected experimentally.