Agegraphic dark energy: growth index and cosmological implications

TL;DR

This paper investigates the cosmological properties and growth of matter fluctuations in the agegraphic dark energy model, comparing its predictions with the standard ΛCDM model at both expansion and perturbation levels.

Contribution

It provides the first analysis of the asymptotic growth index in the homogeneous agegraphic dark energy model and compares clustered versus homogeneous scenarios.

Findings

The growth index asymptotically approaches 5/9 for homogeneous agegraphic dark energy.

Clustered dark energy yields a growth index around 1/2, about 8% smaller than ΛCDM.

The model's parameters are constrained using the latest cosmological data.

Abstract

We study the main cosmological properties of the agegraphic dark energy model at the expansion and perturbation levels. Initially, using the latest cosmological data we implement a joint likelihood analysis in order to constrain the cosmological parameters. Then we test the performance of the agegraphic dark energy model at the perturbation level and we define its difference from the usual $\Lambda$CDM model. Within this context, we verify that the growth index of matter fluctuations depends on the choice of the considered agegraphic dark energy (homogeneous or clustered). In particular, assuming a homogeneous agegraphic dark energy we find, for the first time, that the asymptotic value of the growth index is $\gamma \approx 5/9$, which is close to that of the usual $\Lambda$ cosmology, $\gamma^{(\Lambda)} \approx 6/11$. Finally, if the distribution of dark energy is clustered then we obtain $\gamma \approx 1/2$ which is $\sim 8\%$ smaller than that of the $\Lambda$CDM model.