## Hydrodynamic modes of homogeneous and isotropic fluids

Jan de Boer, Jelle Hartong, Niels A. Obers, Watse Sybesma, Stefan Vandoren

SciPost Phys. 5, 014 (2018) · published 13 August 2018

- doi: 10.21468/SciPostPhys.5.2.014
- Submissions/Reports

### 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. We are thus led to consider the most general fluid assuming only homogeneity and isotropy and study its hydrodynamics and transport behaviour. Remarkably, such systems have not been treated in full generality in the literature so far. Here we study these equations at the linearized level. We find new expressions for the speed of sound, corrections to the Navier-Stokes equation and determine all dissipative and non-dissipative first order transport coefficients. Dispersion relations for the sound, shear and diffusion modes are determined to second order in momenta. In the presence of a scaling symmetry with dynamical exponent z, we show that the sound attenuation constant depends on both shear viscosity and thermal conductivity.

### Cited by 3

### Ontology / Topics

See full Ontology or Topics database.### Authors / Affiliations: mappings to Contributors and Organizations

See all Organizations.-
^{1}Jan de Boer, -
^{1}Jelle Hartong, -
^{2}Niels Obers, -
^{3}Waste Sybesma, -
^{3}Stefan Vandoren

^{1}Institute of Physics, University of Amsterdam [IoP, UvA]^{2}Københavns Universitet / University of Copenhagen [UCPH]^{3}Universiteit Utrecht / University of Utrecht [UU]