Anisotropic minimally interacting dark energy models with cosmic strings and a massive scalar field

This paper deals with the construction of locally rotationally symmetric (LRS) Bianchi type-II (B-II) cosmological models obtained by solving Einstein field equations coupled with an attractive massive scalar field (MSF) when the source of gravitation is the mixture of cosmic string cloud and anisotropic dark energy (DE) fluid which are minimally interacting. We have obtained exact cosmological models by using (i) shear scalar is proportional to the scalar expansion of the space–time and (ii) a power-law relation between the average scale factor of the universe and the scalar field. Our models represent string cosmological model and DE model in the presence of MSF. Using our model, we determine cosmological parameters such as energy densities, deceleration parameter, statefinders and equation of state parameter. We, also, present the tension density and energy density of the string. We discuss the physical aspects of these cosmological parameters. It is observed that our models represent accelerated expansion phenomenon of our universe as confirmed by Supernova Ia experiment.

Kantowski–Sachs universe with dark energy fluid and massive scalar field

This study is mainly concerned with a spatially homogeneous and anisotropic Kantowski–Sachs cosmological model with anisotropic dark energy fluid and massive scalar field. We solve the field equations using (i) the shear scalar proportionality to the expansion scalar and (ii) a mathematical condition that is a consequence of the power law between the scalar field and the average scale factor of the universe, and the corresponding dark energy model is presented. The cosmological parameters of the model are computed and discussed, as well as the relevance of its dynamical aspects to the recent scenario of the accelerated expansion of the universe.

Interactions in the dark sector within the scope of Bianchi type-V model

We are building a cosmological model that has small anisotropy and curvature. For this purpose, the Bianchi type-V (BV) model with dark matter (DM) and anisotropic dark energy (DE) is considered. Assuming a law for deviation from the equation of state (Eos) of DE is linear, we study the transition from decelerated to late accelerated expansion of the Universe. In the proposed model, the linear interaction of the two components alleviates the coincidence problem of the present Universe. Examples of model parameter values compatible with observational data are given.

Anisotropic dark energy models in Brans Dicke theory of gravitation with different expansion laws: A comparative study

In this paper, we have derived the general solutions of the field equations of the Scalar–Tensor theory of gravitation, proposed by Brans and Dicke (1961) within the framework of a locally rotationally symmetric (LRS) metric. We have discussed the anisotropic dark energy models by assuming the time-dependent general scale factor [Formula: see text]. Further, we have discussed the physical and geometric behaviors of the model using different forms of the scale factors. We have also performed a comparative study of the results obtained in various cases. We have observed that the solutions obtained using Hybrid Expansion Law (HEL) are more consistent with recent observations as compared to the rest. Stability of the solutions is also compared using metric perturbations.