HydroClub: Hydrodynamic description of Landau instabilities in superfluid

Superfluid systems are effectively described by hydrodynamics at large scales compared to the local equilibration scales. In general they become unstable once the superfluid velocity reaches an upper bound, which is given by the so-called Landau criterion.

I will explain how one can describe Landau instabilities and the related critical velocity by means of a purely hydrodynamic treatment,without the need to take into consideration the microscopic details of the system (such as the roton modes in Helium 4). To this end I will give a complete description of dissipative superfluid hydrodynamics in the probe limit and of momentum relaxed superfluid hydrodynamics at a nonzero background superfluid velocity. I will show how these instabilities are signaled by the divergence of some static susceptibilities. Furthermore, I will point out how the  hydrodynamic prediction of the critical velocity is confirmed by a holographic model of superfluidity with background superfluid velocity.

Zoom link: https://us06web.zoom.us/j/97266085185?pwd=QzZ4cmlLa29lQ1FCR0RHcXpEMVRIUT09