Breakdown of the linear approximation in the perturbative analysis of heat conduction in relativistic systems

TL;DR

This paper investigates how thermal conduction affects relativistic fluids shortly after symmetry breaking, revealing that the effective inertial mass density can vanish or turn negative, impacting causality considerations.

Contribution

It demonstrates the breakdown of linear approximation in relativistic heat conduction analysis near critical points, highlighting potential issues with causality.

Findings

Effective inertial mass density vanishes at a critical point.

Mass density becomes negative beyond the critical point.

Implications for causality conditions in relativistic fluids.

Abstract

We analyze the effects of thermal conduction in a relativistic fluid just after its departure from spherical symmetry, on a time scale of the order of relaxation time. Using first order perturbation theory, it is shown that, as in spherical systems, at a critical point the effective inertial mass density of a fluid element vanishes and becomes negative beyond that point. The impact of this effect on the reliability of causality conditions is discussed.