Full causal bulk viscous LRS Bianchi I with time varying constants

TL;DR

This paper investigates the evolution of a LRS Bianchi I universe with bulk viscous fluid, where gravitational and speed of light constants vary over time, revealing models with increasing G and c and decreasing negative Lambda.

Contribution

It introduces a model considering time-varying G, c, and Lambda in a bulk viscous universe, highlighting the conditions for physical solutions with ultrastiff matter.

Findings

G and c are increasing functions of time.

Lambda is a negative decreasing function.

Energy density follows ultrastiff matter equation of state.

Abstract

In this paper we study the evolution of a LRS Bianchi I Universe, filled with a bulk viscous cosmological fluid in the presence of time varying constants "but" taking into account the effects of a c-variable into the curvature tensor. We find that the only physical models are those which ``constants'' $G$ and $c$ are growing functions on time $t$, while the cosmological constant $\Lambda$ is a negative decreasing function. In such solutions the energy density obeys the ultrastiff matter equation of state i.e. $\omega=1$.