Growth factor parametrization and modified gravity

Understand

The growth rate of matter perturbation and the expansion rate of the Universe can be used to distinguish modified gravity and dark energy models in explaining the cosmic acceleration.

• The growth rate is parametrized by the growth index $\gamma$.
• We discuss the dependence of $\gamma$ on the matter energy density $\Omega$ and its current value $\Omega_0$ for a more accurate approximation of the growth factor.
• The observational data, including the data of the growth rate, are used to fit different models.