English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

We propose two improved parameterized form for the growth index of the linearmatter perturbations: (I) $\gamma(z)=\gamma_0+(\gamma_{\infty}-\gamma_0){z\overz+1}$ and (II) $\gamma(z)=\gamma_0+\gamma_1\frac{z}{z+1}+(\gamma_{\infty}-\gamma_1-\gamma_0)(\frac{z}{z+1})^{\alpha}$.With these forms of $\gamma(z)$, we analyze the accuracy of the approximationthe growth factor $f$ by $\Omega^{\gamma(z)}_m$ for both the $\omega$CDM modeland the DGP model. For the first improved parameterized form, we find that theapproximation accuracy is enhanced at the high redshifts for both kinds ofmodels, but it is not at the low redshifts. For the second improvedparameterized form, it is found that $\Omega^{\gamma(z)}_m$ approximates thegrowth factor $f$ very well for all redshifts. For chosen $\alpha$, therelative error is below 0.003% for the $\Lambda$CDM model and 0.028% for theDGP model when $\Omega_{m}=0.27$. Thus, the second improved parameterized formof $\gamma(z)$ should be useful for the high precision constraint on the growthindex of different models with the observational data. Moreover, we also showthat $\alpha$ depends on the equation of state $\omega$ and the fractionalenergy density of matter $\Omega_{m0}$, which may help us learn moreinformation about dark energy and DGP models.

Improved parametrization of the growth index for dark energy and DGP models