Cosmological Perturbations in Phantom Dark Energy Models

Abstract

The CDM paradigm, characterised by a constant equation of state w = -1 for dark energy, is the model that better fits observations. However, the same observations strongly support the possibility of a dark energy content where the corresponding equation of state is close to but slightly smaller than -1. In this regard, we focus on three different models where the dark energy content is described by a perfect fluid with an equation of state which can evolve or not. The three proposals show very similar behaviour at present, while the asymptotic evolution of each model drives the Universe to different abrupt events known as (i) Big Rip; (ii) Little Rip (LR); and (iii) Little Sibling of the Big Rip. With the aim of comparing these models and finding possible imprints in their predicted matter distribution, we compute the matter power spectrum and the growth rate fs. We conclude that the model which induces a LR seems to be favoured by observations.