project title: Event horizon for ripplons
project leader: Prof. Ulf Leonhardt
access given (in days): 7
access used (in days): 3
local host: Prof. Grigory Volovik
home institution: University of St Andrews
country of institution: UK
starting date (yyyy-mm-dd): 2008-03-29
Ripplons are gravity waves on the surface of a liquid, or the surface waves at the interface between two superfluids (3He-A and 3He-B). Under condition that the wavelength exceeds the thickness of the liquid layer, the spectrum of ripplons becomes linear function of the wave number, and thus simulates the spectrum of relativistic particles, such as photons. The flow of the liquid produces the effective metric of the effective space in which ripplons move along the geodesic curves. That is why the velocity field simulates the gravity experienced by ripplons. This allows us to construct experimentally the effective metrics which are inreresting for the general relativity, such as horizons of black and white holes, and ergoregion, and to study the problems of quantum fields in the background of such metric fields, including Hawking and Unruh effect of radiation of ripplons. The goal of the project is to discuss possible experimental realizations of the analogs of Hawking radiation and other quantum effects of general relativity in liquids and superfluids.
The studies revealed that the observation of the Hawking radiation in condensed matter system would be possible if there is some special mechanism of amplification of the Hawking radiation. The natural mechanism of amplification is the so called "black hole laser", which can be constructed using two horizons. Corley and Jacobson have shown that in the presence of the black-hole and white-hole horizons the superluminal dispersion leads to an amplification of the particle production in the case of bosons. The formation of pair of the black-hole and white-hole acoustic or ripplon horizons is rather natural in the moving liquids. This opens the prospect of exponentially amplified Hawking radiation.