Black-hole horizon and metric singularity at the brane separating two sliding superfluids
G. E. Volovik
Low Temperature Laboratory, Helsinki University of Technology, FIN-02015 HUT, Finland
Landau Institute for Theoretical Physics RAS, 117940 Moscow, Russia
PACS: 04.50.+h, 04.70.Dy, 47.20.Ft, 67.57.De
Abstract
An analog of black hole can be realized in the low-temperature
laboratory. The horizon can be constructed for the `relativistic' ripplons
(surface waves) living on the brane. The brane is represented by the
interface between two superfluid liquids,
3He-A and 3He-B, sliding along each other without friction. Similar
experimental arrangement has been recently used for the observation and
investigation of the Kelvin-Helmholtz type of instability in superfluids
[Kelvin-HelmholtzInstabilitySuperfluids]. The
shear-flow instability in superfluids is characterized by two critical
velocities. The lowest threshold measured in recent experiments
[Kelvin-HelmholtzInstabilitySuperfluids] corresponds to
appearance of the ergoregion for ripplons. In the
modified geometry this will give rise to the black-hole event horizon
in the effective metric experienced by ripplons. In the region
behind the horizon, the brane vacuum is unstable due to interaction with
the higher-dimensional world of bulk superfluids. The time of the
development of instability can be made very long at low temperature. This
will allow us to reach and investigate the second critical velocity - the
proper Kelvin-Helmholtz instability threshold. The latter corresponds to
the singularity inside the black hole, where the determinant of the
effective metric becomes infinite.