Bulk viscous FWR with time varying constants revisited

TL;DR

This paper investigates a cosmological model with flat FRW symmetry where gravitational and cosmological constants vary over time, analyzing the effects of a variable speed of light on the field equations and thermodynamics.

Contribution

It identifies specific power-law forms of G, c, and Lambda that make the field equations integrable, revealing a relationship G/c^2 = constant and the behavior of these constants over time.

Findings

G and c are found to grow over time.

Lambda decreases as a negative function.

The model's thermodynamics are consistent with these varying constants.

Abstract

We study a full causal bulk viscous cosmological model with flat FRW symmetries and where the ``constants'' $G,c$ and $\Lambda $ vary. We take into account the possible effects of a $c-$variable into the curvature tensor in order to outline the field equations. Using the Lie method we find the possible forms of the ``constants'' $G$ and $c$ that make integrable the field equations as well as the equation of state for the viscous parameter. It is found that $G,c$ and $\Lambda $ follow a power law solution verifying the relationship $G/c^{2}=\kappa .$ Once these possible forms have been obtained we calculate the thermodynamical quantities of the model in order to determine the possible values of the parameters that govern the quantities, finding that only a growing $G$ and $c$ are possible while $% \Lambda $ behaves as a negative decreasing function.