Anisotropic cosmological models with perfect fluid and dark energy revisited

TL;DR

This paper revisits anisotropic Bianchi type-I cosmological models incorporating perfect fluid and dark energy, deriving exact solutions that describe universes with various geometries and singularity properties.

Contribution

It provides new exact solutions for Bianchi type-I models with mixed fluids, exploring their implications for universe geometry and evolution.

Findings

Universe can be spatially finite or infinite depending on parameters.

Models include both singular and oscillatory non-singular solutions.

Dark energy influences the universe's anisotropy and evolution.

Abstract

We consider a self-consistent system of Bianchi type-I (BI) gravitational field and a binary mixture of perfect fluid and dark energy. The perfect fluid is taken to be the one obeying the usual equation of state, i.e., $p = \zeta \ve$, with $\zeta \in [0, 1]$ whereas, the dark energy is considered to be obeying a quintessence-like equation of state. Exact solutions to the corresponding Einstein equations are obtained. The model in consideration gives rise to a Universe which is spatially finite. Depending on the choice of problem parameters the Universe is either close with a space-time singularity, or an open one which is oscillatory, regular and infinite in time.