Black hole analogue produces sonic Hawking radiation

New Scientist : In 2009, Jeff Steinhauer of the Technion–Israel Institute of Technology in Haifa and his colleagues made a model of a black hole using a Bose–Einstein condensate (BEC) and a pair of lasers. The first laser held the BEC in a narrow tube, and the second accelerated a portion of the material so that it flowed faster than the speed of sound. That created two horizons, one where the material transitioned from still to supersonic and another inside that one where the material slowed again. Now Steinhauer’s group says that they have seen an analogue to Hawking radiation —the release of particles due to quantum effects near a black hole’s event horizon. For their sonic black hole, the radiation is in the form of phonons , “particles” of sound, which are created in pairs, with one phonon escaping and the other being trapped between the two horizons. It is the trapped phonons that the researchers saw, because as the particles bounce between the horizons, they create more phonon pairs, which amplifies the signal to the point that it could be detected.