On the mode structure of imperfect fluids

TL;DR

This paper explores the mode structure of imperfect fluids in relativistic thermodynamics, comparing the causal MIS theory with the traditional Eckart theory to clarify their differences in long-wavelength perturbations.

Contribution

It provides a simplified, pedagogical analysis of the mode structure in relativistic non-equilibrium thermodynamics, focusing on the relation between MIS and Eckart theories.

Findings

Clarifies the relation between long-wavelength modes of MIS and Eckart theories.

Highlights essential features without requiring full formalism of the complete theory.

Provides insights into the stability and behavior of relativistic imperfect fluids.

Abstract

This paper tries to obtain a simple picture of several aspects of the mode structure in relativistic non-equilibrium thermodynamics. Its pedagogical focus is on the relation between long-wavelength perturbation modes of the causal M\"{u}ller-Israel-Stewart (MIS) theory and those of the traditional Eckart theory. Principally, this issue was clarified in a series of papers by Hiscock and Lindblom (see [8-10]). Here, I put together some essential features which do not require the entire formalism of the complete theory.