GRASP seminar, Benjamin APFFEL, 21/3/22: "Wave propagation in time-varying media: from frequency conversion to inverted buoyancy"
Benjamin Apffel (ESPCI, Paris) will give a presentation entitled "Wave propagation in time-varying media: from frequency conversion to inverted buoyancy" in the next GRASP seminar that will take place on Monday 21 March 2022 at 9.00 in room 3/14 (B5a building).
Wave propagation in time varying media offers several original properties compared to wave propagation in static media. During this presentation, I will show several experimental implementation of such media for surface waves. After a short introduction on time-varying media, two particular regime will be discussed. When the modulation is slow compared to the wave propagation, we show that arbitrary frequency conversion of an initial wave packet can be achieved. In contrary when the modulation is fast, an effective medium theory arises and the dispersion relation of the waves is modified compared to the non-modulated case. In particular unstable modes can be stabilized by the modulation, opening the way for the creation of levitating liquid layers of typically ten centimeters.