The $\Lambda$CDM growth rate of structure revisited

TL;DR

This paper re-evaluates the growth rate of cosmic structures in the standard $\Lambda$CDM model using recent observational data, testing different models for the growth index and improving parameter constraints.

Contribution

It introduces a comprehensive analysis of multiple growth index models with updated data, enhancing the understanding of structure formation in cosmology.

Findings

Adding recent growth data improves statistical constraints.

Constant growth index yields $\Omega_{m0}=0.273 ext{ and }\gamma=0.586$.

Multiple models are statistically compared against observations.

Abstract

We re-examine the growth index of the concordance $\Lambda$ cosmology in the light of the latest 6dF and {\em WiggleZ} data. In particular, we investigate five different models for the growth index $\gamma$, by comparing their cosmological evolution using observational data of the growth rate of structure formation at different redshifts. Performing a joint likelihood analysis of the recent supernovae type Ia data, the Cosmic Microwave Background shift parameter, Baryonic Acoustic Oscillations and the growth rate data, we determine the free parameters of the $\gamma(z)$ parametrizations and we statistically quantify their ability to represent the observations. We find that the addition of the 6dF and {\em WiggleZ} growth data in the likelihood analysis improves significantly the statistical results. As an example, considering a constant growth index we find $\Omega_{m0}=0.273\pm 0.011$ and $\gamma=0.586^{+0.079}_{-0.074}$.