A class of transient acceleration models consistent with Big Bang Cosmology

Abstract

Is it possible that the current cosmic accelerating expansion will turn into a decelerating one? Can this transition be realized by some viable theoretical model that is consistent with the standard Big Bang cosmology? We study a class of phenomenological models of a transient acceleration, based on a dynamical dark energy with a very general form of equation of state $p_{de}=\alpha\rho_{de}-\beta\rho_{de}^m$. It mimics the cosmological constant $\rho_{de}\rightarrow$ const for small scale factor $a$, and behaves as a barotropic gas with $\rho_{de}\rightarrow a^{-3(\alpha+1)}$ with $\alpha\ge 0$ for large $a$. The cosmic evolution of four models in the class has been examined in details, and all yields a smooth transient acceleration. Depending on the specific model, the future universe may be dominated either by the dark energy or by the matter. In two models, the dynamical dark energy can be explicitly realized by a scalar field with an analytical potential $V(\phi)$. Moreover, the statistical analysis shows that the models can be as robust as $\Lambda$CDM in confronting the observational data of SN Ia, CMB, and BAO. As improvements over the previous studies, our models overcome the over-abundance problem of dark energy during early eras, and satisfy the constraints on the dark energy from WMAP observations of CMB.