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Résumé |
When the velocity of flowing water surpasses the speed of surface waves, these propagate in exactly the same way as radiation near a black hole horizon. In particular, it is in theory possible to reproduce in such systems the (classical) analog of the Hawking effect. Unfortunately, it is in practice quite hard to obtain controllable flows that reach the wave velocity. It turns out that if the flow accelerates, even below the threshold velocity, there is still an imprint of the Hawking effect, which has been experimentally observed in Vancouver and in Poitiers. I will describe the nature of this imprint, as well as its spectrum for low frequency waves. In particular, I will show that the production of Hawking-like modes is governed by a new type of horizon, which is reached for complex values of the position. This “complex horizon” governs both the region of this mode production and its spectrum. |
