Dynamical dark energy models with singularities in the view of the forthcoming results of the growth observations

Abstract

The question of the origin of the recent acceleration of the Universes expansion is still pending. What is making the situation even worst, it is impossible to distinguish the vast majority of the proposed models of the dynamical dark energy and modified gravity from the $\Lambda CDM$ in view of recent geometrical and dynamical, observational data. On the other hand on scales much smaller than the present Hubble scale, there are differences in the growth of the matter perturbations for different modes of the perturbations in the $\Lambda CDM$. In the view of the new planned observations that will give insight into the perturbations of the dark sector this issue is being worth of further investigation. We analyze the evolution of the dark matter perturbations in the dynamical dark energy models with the singularities, such as the sudden future singularity and the finite scale factor singularity. We employ the Newtonian gauge formulation for derivation of the perturbation equations for the growth function. We abandon the sub-Hubble approximation, what leads to the scale dependent solutions for the perturbations. Treating the growth function as a scale dependent allows to differentiate the dynamical dark energy models with the singularities and the dynamical dark energy models and the $\Lambda CDM$. The new data constraining growth of the perturbations will be able to rule out the whole range of the values of the parameters allowed by the present data of the dynamical dark energy models with the sudden future singularity and the finite scale factor singularity.