title: Hawking-like radiation does not require a trapped region.
abstract: We discuss the issue of quasiparticle production by "analogue black holes" with particular attention paid to the possibility of reproducing Hawking radiation in a laboratory. By constructing simple geometric acoustic models, we obtain a somewhat unexpected result: We show that, in order to obtain a stationary and Planckian emission of quasiparticles, it is not necessary to create a trapped region in the acoustic spacetime (corresponding to a supersonic regime in the fluid flow). It is sufficient to set up a dynamically changing flow asymptotically approaching a sonic regime with sufficient rapidity in laboratory time. This result is generic to curved-space quantum field theory, the "analogue spacetimes" we consider providing a guide to physical intuition, and a possible route to laboratory experiments.
authors.affiliation: Instituto de Astrofísica de Andalucía, CSIC, Camino Bajo de Huétor 50, 18008 Granada, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Barceló
authors.forename: Stefano
authors.initials: S
authors.lastname: Liberati
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Sonego
authors.forename: Matt
authors.initials: M
authors.lastname: Visser