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We analyze the global behaviour of the growth index of cosmic inhomogeneities in an isotropic homogeneous universe filled by cold non-relativistic matter and dark energy (DE) with an arbitrary equation of state. Using a dynamical system approach, we find the critical points of the system. That unique trajectory for which the growth index $gamma$ is finite from the asymptotic past to the asymptotic future is identified as the so-called heteroclinic orbit connecting the critical points $(Omega_m=0,~gamma_{infty})$ in the future and $(Omega_m=1,~gamma_{-infty})$ in the past. The first is an attractor while the second is a saddle point, confirming our earlier results. Further, in the case when a fraction of matter (or DE tracking matter) $varepsilon Omega^{rm tot}_m$ remains unclustered, we find that the limit of the growth index in the past $gamma_{-infty}^{varepsilon}$ does not depend on the equation of state of DE, in sharp contrast with the case $varepsilon=0$ (for which $gamma_{-infty}$ is obtained). We show indeed that there is a mathematical discontinuity: one cannot obtain $gamma_{-infty}$ by taking $lim_{varepsilon to 0} gamma^{varepsilon}_{-infty}$ (i.e. the limits $varepsilonto 0$ and $Omega^{rm tot}_mto 1$ do not commute). We recover in our analysis that the value $gamma_{-infty}^{varepsilon}$ corresponds to tracking DE in the asymptotic past with constant $gamma=gamma_{-infty}^{varepsilon}$ found earlier.
We derive for the first time the growth index of matter perturbations of the FLRW flat cosmological models in which the vacuum energy depends on redshift. A particularly well motivated model of this type is the so-called quantum field vacuum, in whic
We study how the cosmological constraints from growth data are improved by including the measurements of bias from Dark Energy Survey (DES). In particular, we utilize the biasing properties of the DES Luminous Red Galaxies (LRGs) and the growth data
The observational fact that the present values of the densities of dark energy and dark matter are of the same order of magnitude, $rho_{de0}/rho_{dm0} sim mathcal{O}(1)$, seems to indicate that we are currently living in a very special period of the
We investigate the cosmology of massive spinor electrodynamics when torsion is non-vanishing. A non-minimal interaction is introduced between the torsion and the vector field and the coupling constant between them plays an important role in subsequen
The field equations in FRW background for the so called C-theories are presented and investigated. In these theories the usual Ricci scalar is substituted with $f(mathcal{R})$ where $mathcal{R}$ is a Ricci scalar related to a conformally scaled metri