Viscous dissipative effects in isotropic brane cosmology

TL;DR

This paper investigates how viscous dissipative effects influence the evolution of isotropic brane cosmologies within the Randall-Sundrum framework, highlighting entropy production and non-inflationary dynamics.

Contribution

It provides exact solutions for viscous brane cosmologies using full causal thermodynamics, extending understanding of dissipative effects in higher-dimensional models.

Findings

Solutions describe non-inflationary brane worlds starting from a singular state

Viscous dissipation leads to increasing entropy over time

Large entropy production occurs due to viscous effects

Abstract

We consider the dynamics of a viscous cosmological fluid in the generalized Randall-Sundrum model for an isotropic brane. To describe the dissipative effects we use the Israel-Hiscock-Stewart full causal thermodynamic theory. In the limiting case of a stiff cosmological fluid with pressure equal to the energy density, the general solution of the field equations can be obtained in an exact parametric form for a cosmological fluid with constant bulk viscosity and with a bulk viscosity coefficient proportional to the square root of the energy density, respectively. The obtained solutions describe generally non-inflationary brane worlds, starting from a singular state. During this phase of evolution the comoving entropy of the Universe is an increasing function of time, and thus a large amount of entropy is created in the brane world due to viscous dissipative processes.