title: Instability of the Superfluid Flow as Black-Hole Lasing Effect.
abstract: We show that the critical velocity of a superfluid flow through a penetrable barrier coincides with the onset of the analog black-hole lasing effect. This dynamical instability is triggered by modes resonating in an effective cavity formed by two horizons enclosing the barrier. The location of the horizons is set by v(x)=c(x), with v(x),c(x) being the local fluid velocity and sound speed, respectively. We compute the critical velocity analytically and show that it is univocally determined by the configuration of the horizons. In the limit of broad barriers, the continuous spectrum at the origin of the Hawking-like radiation and of the Landau energetic instability is recovered.
authors.affiliation: Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot-Paris 7 and CNRS, Bâtiment Condorcet, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France.
authors.forename: S
authors.initials: S
authors.lastname: Finazzi
authors.affiliation: Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Piazza
authors.affiliation: INO-CNR BEC Center and Dipartimento di Fisica, Università di Trento, 38123 Povo, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Abad
authors.affiliation: QSTAR, INO-CNR and LENS, Largo Enrico Fermi 2, 50125 Firenze, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Smerzi
authors.affiliation: Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany.|INO-CNR BEC Center and Dipartimento di Fisica, Università di Trento, 38123 Povo, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Recati