Anisotropic Dark Energy Research Articles

LRS Bianchi type I models with anisotropic dark energy and constant deceleration parameter

Locally rotationally symmetric (LRS) Bianchi Type I cosmological models are examined in the presence of dynamically anisotropic dark energy and perfect fluid. We assume that the dark energy (DE) is minimally interacting, has dynamical energy density, anisotropic equation of state parameter (EoS). The conservation of the energy-momentum tensor of the DE is assumed to consist of two separately additive conserved parts. A special law is assumed for the deviation from isotropic EoS, which is consistent with the assumption on the conservation of the energy-momentum tensor of the DE. Exact solutions of Einstein's field equations are obtained by assuming a special law of variation for the mean Hubble parameter, which yields a constant value of the deceleration parameter. Geometrical and kinematic properties of the models and the behaviour of the anisotropy of the dark energy has been carried out. The models give dynamically anisotropic expansion history for the universe that allows to fine tune the isotropization of the Bianchi metric, hence the CMB anisotropy.

Stable gravastars of anisotropic dark energy

Dynamical models of prototype gravastars made of anisotropic dark energy fluid are constructed, in which an infinitely thin spherical shell of a perfect fluid with the equation of state p = (1−γ)σ divides the whole spacetime into two regions, the internal region is filled with an anisotropic dark energy fluid, and the external region is the Schwarzschild. It is found that in some cases the models represent the ``bounded excursion''stable gravastars, where the thin shell is oscillating between two finite radii, while in other cases they collapse until the formation of black holes or normal stars. In the phase space, the region for the ``bounded excursion'' gravastars is very small in comparison to that of black holes, but not empty, as found in our previous papers. Therefore, although the existence of gravastars can not be completely excluded from current analysis, the opposite is not possible either,that is, even if gravastars exist, they do not exclude the existence of black holes.