Sonic holes in Bose-Einstein Condensates
Dr. Alessio Recati (INO-CNR BEC Center and Dipartimento di Fisica, Università di Trento & TUM München)

In this talk I review some recent results concerning the effects of the coexistence of supersonic and subsonic regions — a.k.a sonic holes — in a flowing Bose-Einstein Condensates (BECs).
The analogies with models in gravitation, like Hawking radiation and the Jacobson-Corley black hole laser are pointed out.
In particular:
(i) The analogy between Hawking-like radiation and Bogoliubov modes is discussed in details. Correlated photons from the sonic horizon give rise to new signatures in the inner-hole - outer-hole density correlation functions.
(ii) Casimir-like photon emission in the process of generating the sonic hole is produced.
Experiment on the measurement of the emitted correlated photons due to vacuum change have been performed by the group of Chris Westbrook in Paris.
(iii) Very recently a first experimental evidence has been reported by Jeff Steinauer at Technion on a BEC equivalent of a black-hole laser.
I will show that such instability is at the origin of the long-standing problem of the current decay of a compressible superfluid through a barrier.