The growth index of matter perturbations using the clustering of dark energy

Abstract

We have put forward a new unified framework which provides a consistent and rather complete account of the growth index of matter perturbations in the regime where the dark energy is allowed to have clustering. In particular, we find that the growth index is not only affected by the cosmological parameters but rather it depends on the choice of the considered dark energy (homogeneous or clustered). Using the Planck priors and performing a standard χ 2 -minimization between theoretical expectations and growth data, we statistically quantify the ability of the growth index to represent the observations. Finally, based on the growth index analysis we find that the growth data favor the clustered dark energy scenario.

Constraints to Dark Energy Using PADE Parameterizations

“…Moreover, the growth of cosmic structures are also affected by perturbations of DE when we deal with dynamical DE models with time varying EoS parameter w 1 de ¹ - (Erickson et al 2002;Bean & Doré 2004;Hu & Scranton 2004;Basilakos & Voglis 2007;Mota et al 2007;Ballesteros & Riotto 2008;Basilakos et al 2009aBasilakos et al , 2010Gannouji et al 2010;Sapone & Majerotto 2012;Batista & Pace 2013;Dossett & Ishak 2013;Basse et al 2014;Batista 2014;Nesseris & Sapone 2015;Pace et al 2014aPace et al , 2014bBasilakos 2015;Mehrabi et al 2015aMehrabi et al , 2015bMehrabi et al , 2015cMalekjani et al 2015Malekjani et al , 2017.…”

“…In particular, we can set up a more general formalism in which the background expansion data, including SN Ia, BAO, CMB shift parameter, Hubble expansion data, joined with the growth rate data of LSSs in order to put constraints on the parameters of cosmology and DE models (see Cooray et al 2004;Corasaniti et al 2005;Mota et al 2007Mota et al , 2008Basilakos et al 2010;Gannouji et al 2010;Mota et al 2010;Blake et al 2011b;Nesseris et al 2011;Basilakos & Pouri 2012;Chuang et al 2013;Contreras et al 2013;Llinares & Mota 2013;Llinares et al 2014;Li et al 2014;Yang et al 2014;Basilakos 2015;Mehrabi et al 2015aMehrabi et al , 2015bBasilakos 2016;Bonilla Rivera & Farieta 2016;Fay 2016;Malekjani et al 2017).…”

Dark energy homogeneity in general relativity: Are we applying it correctly?

“…This may be owing to the behaviour of w x for homCPL, which suggests that DE sets in relatively earlier for the homCPL -hence causing the matter perturbations to have less time to cluster, thereby resulting in relatively lower power spectra. Obviously, Case 1 (38) implies that for equal values of c 2 sx , the difference between a homogeneous DE and a clustering DE is mainly governed by the background, with little to do with the perturbations. However, one may expect that this difference strongly pertains perturbations, and that a homogeneous DE results in higher power spectra on large scales, relative to a clustering DE -given that the perturbative effect of the homogeneous DE should be negligible (or even absent).…”

“…Thus by Eq. (42), c 2 ax = c 2 sx , which then disallows Case 1 (38). Therefore, w x may oscillate (see, e.g.…”

“…Thus Case 2 (43), being defined in comoving gauge, can lead to (physical) observable implications in the power spectrum. Moreover, the effect of Case 2 (43) on the matter perturbations will be imposed directly, rather than indirectly via the background evolutions -as in Case 1 (38). This way, the imprint of the given homogeneous DE will bear directly on the growth of structure.…”