FTheory: Hawking Radiation in Fluid Flows
The emission of thermal radiation by black holes, discovered by Hawking, is now a broadly accepted and major prediction of quantum field theory in curved space-times. In 81, Unruh showed that sound waves in a moving fluid propagate exactly like the radiation field in a curved geometry, and proposed to test the Hawking mechanism in fluid flows.
I will discuss under which conditions the Hawking process is recovered in black hole flows, and what replaces the relativistic notion of horizon. In white hole flows, despite the similarity of the scattering problem, a specific and new physical phenomenon occurs. The large amplification of low frequencies through the Hawking effect leads to the emission of a large, classical wave of zero frequency but finite wavelength. We present the properties of this wave, and its birth, when it is triggered by quantum or thermal fluctuations.