On the equivalence of nonadiabatic fluids

TL;DR

This paper demonstrates that under certain conditions, anisotropic and isotropic nonadiabatic fluids in spherical symmetry can be equivalent, providing a new approximation method for studying dissipative fluids.

Contribution

It establishes a theoretical equivalence between anisotropic and isotropic nonadiabatic fluids and introduces a numerical model illustrating this relationship.

Findings

Quantitative differences are minimal between the two fluid types.

Equivalence depends on specific initial-boundary conditions.

The approach offers a first order approximation for dissipative fluid studies.

Abstract

Here we show how an anisotropic fluid in the diffusion limit can be equivalent to an isotropic fluid in the streaming out limit, in spherical symmetry. For a particular equation of state this equivalence is total, from one fluid we can obtain the other and vice versa. A numerical master model is presented, based on a generic equation of state, in which only quantitative differences are displayed between both nonadiabatic fluids. From a deeper view, other difference between fluids is shown as an asymmetry that can be overcome if we consider the appropriate initial-boundary conditions. Equivalence in this context can be considered as a first order method of approximation to study dissipative fluids.