Bianchi type-II models in the presence of perfect fluid and anisotropic dark energy

Abstract

Spatially homogeneous but totally anisotropic and non-flat Bianchi type II cosmological model has been studied in general relativity in the presence of two minimally interacting fluids; a perfect fluid as the matter fluid and a hypothetical anisotropic fluid as the dark energy fluid. The Einstein's field equations have been solved by applying two kinematical ansätze: we have assumed the variation law for the mean Hubble parameter that yields a constant value of deceleration parameter, and one of the components of the shear tensor has been considered proportional to the mean Hubble parameter. We have particularly dwelled on the accelerating models with non-divergent expansion anisotropy as the Universe evolves. Yielding anisotropic pressure, the fluid we consider in the context of dark energy, can produce results that can be produced in the presence of isotropic fluid in accordance with the ΛCDM cosmology. However, the derived model gives additional opportunities by being able to allow kinematics that cannot be produced in the presence of fluids that yield only isotropic pressure. We have obtained well behaving cases where the anisotropy of the expansion and the anisotropy of the fluid converge to finite values (include zero) in the late Universe. We have also showed that although the metric we consider is totally anisotropic, the anisotropy of the dark energy is constrained to be axially symmetric, as long as the overall energy momentum tensor possesses zero shear stress.

Second law of gravitational thermodynamics in the locally rotationally symmetric Bianchi type-II universe

“…Kumar and Akarsu [54] showed that the anisotropy of the dark energy is constrained to be axially symmetric considering Bianchi type-II models.…”

Statefinder Diagnostic for Binary Mixture of Anisotropic Dark Energy and Perfect Fluid in Bianchi Type-IX Universe

“…where p and  are the pressure and energy density of DE and  is an EoS parameter which is useful to describe cosmic acceleration. A number of authors [7][8][9][10][11][12][13][14][15] have studied binary mixture of perfect fluid (PF) and anisotropic DE for Bianchi type-I, II, III, V, VI0, plane symmetric, kaluza-klein as well as higher dimensional cosmological models too. Recently, the anisotropic dark energy has been studied for Bianchi type-IX space-time [16].…”

Anisotropic bulk viscous string cosmological models of the Universe under a time-dependent deceleration parameter

“…Recently, Asseo and Sol [13] and Roy & Banerjee [14] stressed the importance of B-type-II and proscribed LRS cosmological model. Kumar and Akarsu [15] mentioned B-type-II universe with anisotropic dark energy and perfect fluid. Wang [16]− [18] has investigated the models of Letelier-type within the theoretical account of LRS B-type-II.…”