In 74, Hawking derived one of the main predictions of quantum field theory in curved spacetimes. He showed that black holes should emit a steady and thermal flux of particles. Later, Unruh proposed to mimic the behavior of fields around black hole geometries by looking at perturbations waves on a moving fluid. A fluid whose velocity crosses the speed of sound behaves much like a horizon, where the Hawking effect can be studied.
In this talk, we first present the general ideas of analog models. To study the Hawking effect, the infinite redshift on the horizon forces us to take into account the necessary violations of Lorentz invariance at short wavelengths. Using improved WKB technics, we establish under which conditions the Hawking process is recovered in black or white hole flows.
In a second part, we study a peculiar effect specific to analog white hole flows. We show that in this background, 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. If time allows it, we will also discuss modifications introduced when the excitation field is massive.
