Sound waves and spontaneous oscillations in polar active matter
I will experimentally demonstrated how sound waves almost freely propagate in active colloidal liquid despite the strongly over-damped dynamics of its elementary units. I will then show how to fully infer the hydrodynamics of this
spontaneously flowing liquid from its fluctuation spectrum. Finally I will address and elucidate the intrinsically nonlinear response of flocking phases and show how it can be exploited to devise autonomous oscillators.