HET Journal club: Niels Obers

Speaker: Niels Obers

Title: Hydrodynamics for Homogeneous and Isotropic Media

Abstract: Relativistic fluids are Lorentz invariant, and a non-relativistic limit of such fluids leads to the well-known Navier-Stokes equation. However, for fluids moving with respect to a reference system, or in critical systems with generic dynamical exponent z, the assumption of Lorentz invariance (or its non-relativistic version) does not hold. In this talk I will discuss a more general theory of fluids assuming only homogeneity and isotropy. Remarkably, such systems have not been treated in full generality in the literature so far. I will first consider this at the perfect fluid level, which includes a more general stress tensor, corresponding corrections to the Euler equations for boost non-invariant systems as well
as new expressions for the the speed of sound. As a concrete illustration, the case of ideal classical and quantum Lifshitz gasses will be exhibited. If time permits, I will briefly turn to the transport behavior of such fluids, 
corrections to the Navier-Stokes equation,  along with the determination of all dissipative and non-dissipative first order transport coefficients and their effect on the sound, shear and diffusion modes.