Accelerating dark energy models with anisotropic fluid in Bianchi type-$VI_{0}$ space-time

TL;DR

This paper presents two accelerating dark energy models within Bianchi type-$VI_{0}$ space-time featuring anisotropic fluids, demonstrating transition from deceleration to acceleration, compatibility with observations, and stability of solutions.

Contribution

It introduces novel anisotropic dark energy models in Bianchi type-$VI_{0}$ space-time with a specific scale factor, showing their observational viability and late-time isotropization.

Findings

Models exhibit transition from deceleration to acceleration.

Dark energy EoS parameter is time-dependent and observationally consistent.

Cosmological constant decreases over time, approaching a small positive value.

Abstract

Motivated by the increasing evidence for the need of a geometry that resembles Bianchi morphology to explain the observed anisotropy in the WMAP data, we have discussed some features of the Bianchi type-$VI_{0}$ universes in the presence of a fluid that wields an anisotropic equation of state (EoS) parameter in general relativity. We present two accelerating dark energy (DE) models with an anisotropic fluid in Bianchi type-$VI_{0}$ space-time. To prevail the deterministic solution we choose the scale factor $a(t) = \sqrt{t^{n}e^{t}}$, which yields a time-dependent deceleration parameter (DP), representing a class of models which generate a transition of the universe from the early decelerating phase to the recent accelerating phase. Under the suitable condition, the anisotropic models approach to isotropic scenario. The EoS for dark energy $\omega$ is found to be time-dependent and its existing range for derived models is in good agreement with the recent observations of SNe Ia data (Knop et al. 2003), SNe Ia data with CMBR anisotropy and galaxy clustering statistics (Tegmark et al. 2004) and latest combination of cosmological datasets coming from CMB anisotropies, luminosity distances of high redshift type Ia supernovae and galaxy clustering (Hinshaw et al. 2009; Komatsu et al. 2009). For different values of $n$, we can generate a class of physically viable DE models.The cosmological constant $\Lambda$ is found to be a positive decreasing function of time and it approaches to a small positive value at late time (i.e. the present epoch) which is corroborated by results from recent type Ia supernovae observations. We also observe that our solutions are stable. The physical and geometric aspects of both the models are also discussed in detail.