arXiv2015
We apply the statefinder hierarchy plus the fractional growth parameter to explore the extended Ricci dark energy (ERDE) model, in which there are two independent coefficients $α$ and $β$. By adjusting them, we plot evolution trajectories of some typical parameters, including Hubble expansion rate $E$, deceleration parameter $q$, the third and fourth order hierarchy $S_3^{(1)}$ and $S_4^{(1)}$ and fractional growth parameter $ε$, respectively, as well as several combinations of them. For the case of variable $α$ and constant $β$, in the low-redshift region the evolution trajectories of $E$ are in high degeneracy and that of $q$ separate somewhat. However, the $Λ$CDM model is confounded with ERDE in both of these two cases. $S_3^{(1)}$ and $S_4^{(1)}$, especially the former, perform much better. They can differentiate well only varieties of cases within ERDE except $Λ$CDM in the low-redshift region. For high-redshift region, combinations $\{S_n^{(1)},ε\}$ can break the degeneracy. Both of $\{S_3^{(1)},ε\}$ and $\{S_4^{(1)},ε\}$ have the ability to discriminate ERDE with $α=1$ from $Λ$CDM, of which the degeneracy cannot be broken by all the before-mentioned parameters. For the case of variable $β$ and constant $α$, $S_3^{(1)}(z)$ and $S_4^{(1)}(z)$ can only discriminate ERDE from $Λ$CDM. Nothing but pairs $\{S_3^{(1)},ε\}$ and $\{S_4^{(1)},ε\}$ can discriminate not only within ERDE but also ERDE from $Λ$CDM. Finally we find that $S_3^{(1)}$ is surprisingly a better choice to discriminate within ERDE itself, and ERDE from $Λ$CDM as well, rather than $S_4^{(1)}$.