The Rayleigh-Brillouin Spectrum in Special Relativistic Hydrodynamics

TL;DR

This paper compares three relativistic thermodynamics models by calculating the Rayleigh-Brillouin spectrum, finding that Eckart's model predicts no spectrum, thus questioning its validity and highlighting the need for further investigation.

Contribution

It evaluates the Rayleigh-Brillouin spectrum in relativistic fluids across three models, revealing differences and challenging Eckart's approach.

Findings

Eckart's model predicts no spectrum, questioning its validity.

Two alternative models produce finite spectra, differing from each other.

The results prompt further examination of relativistic non-equilibrium thermodynamics.

Abstract

In this paper we calculate the Rayleigh-Brillouin spectrum for a relativistic simple fluid according to three different versions available for a relativistic approach to non-equilibrium thermodynamics. An outcome of these calculations is that Eckart's version predicts that such spectrum does not exist. This provides an argument to question its validity. The remaining two results, which differ one from another, do provide a finite form for such spectrum. This raises the rather intriguing question as to which of the two theories is a better candidate to be taken as a possible version of relativistic non-equilibrium thermodynamics. The answer will clearly require deeper examination of this problem.