Anisotropic cosmologies with ghost dark energy models in f (R, T) gravity

Abstract.

In this work, the generalized Quantum Chromodynamics (QCD) ghost model of dark energy in the framework of Einstein gravity is investigated. For this purpose, we use the squared sound speed $v_{s}^{2}$ whose sign determines the stability of the model. At first, the non-interacting ghost dark energy in a Bianchi type-I (BI) background is discussed. Then the equation-of-state parameter, $\omega_D=p_{D}/\rho_{D}$, the deceleration parameter, and the evolution equation of the generalized ghost dark energy are obtained. It is shown that the equation-of-state parameter of the ghost dark energy can cross the phantom line ( $\omega=-1$ in some range of the parameter spaces. Then, this investigation was extended to the general scheme for modified $f(R,T)$ gravity reconstruction from a realistic case in an anisotropic Bianchi type-I cosmology, using the dark matter and ghost dark energy. Special attention is taken into account for the case in which the function f is given by $f(R,T)=f_{1}(R) +f_{2}(T)$. We consider a specific model which permits the standard continuity equation in this modified theory. Besides $\Omega_{\Lambda}$ and $\Omega$ in standard Einstein cosmology, another density parameter, $\Omega_{\sigma}$, is expected by the anisotropy. This theory implies that if $\Omega_{\sigma}$ is zero then it yields the FRW universe model. Interestingly enough, we find that the corresponding f (R, T) gravity of the ghost DE model can behave like phantom or quintessence of the selected models which describe the accelerated expansion of the universe.