On Radiative Fluids in Anisotropic Spacetimes

TL;DR

This paper applies Israel-Stewart theory to a radiative fluid in anisotropic cosmology, examining its evolution and role in the Universe's expansion, showing it approaches thermal equilibrium slowly and does not explain acceleration.

Contribution

It demonstrates the late-time behavior of radiative fluids in anisotropic spacetimes using a realistic thermodynamic model, contrasting previous mathematical fluid models.

Findings

Radiative fluid approaches thermal equilibrium slowly at late times.

Transport properties alone do not account for accelerated expansion.

The model provides realistic insights into early Universe dissipative phenomena.

Abstract

We apply the second-order Israel-Stewart theory of relativistic fluid- and thermodynamics to a physically realistic model of a radiative fluid in a simple anisotropic cosmological background. We investigate the asymptotic future of the resulting cosmological model and review the role of the dissipative phenomena in the early Universe. We demonstrate that the transport properties of the fluid alone, if described appropriately, do not explain the presently observed accelerated expansion of the Universe. Also, we show that, in constrast to the mathematical fluid models widely used before, the radiative fluid does approach local thermal equilibrium at late times, although very slowly, due to the cosmological expansion.