The Universe With Bulk Viscosity

TL;DR

This paper derives exact solutions for an anisotropic universe model incorporating bulk viscosity, variable gravitational constant, and cosmological constant, revealing inflationary behavior, isotropization, and evolving fundamental constants over cosmic time.

Contribution

It introduces new exact solutions for a universe with variable G, Λ, and bulk viscosity, highlighting their dynamic evolution and impact on cosmic expansion and isotropization.

Findings

Universe isotropizes during expansion

Gravitational constant increases over time

Cosmological constant decreases as t^{-2}

Abstract

Exact solutions for a model with variable $G$, $\Lambda$ and bulk viscosity are obtained. Inflationary solutions with constant (de Sitter-type) and variable energy density are found. An expanding anisotropic universe is found to isotropize during its course of expansion but a static universe is not. The gravitational constant is found to increase with time and the cosmological constant decreases with time as $\Lambda \propto t^{-2}$.