The growth factor of matter perturbations in an f(R) gravity

TL;DR

This paper investigates the growth of matter perturbations in a specific f(R) gravity model, using observational data to constrain the model and assess its consistency with current cosmological measurements.

Contribution

It introduces three parametric forms of the growth index and evaluates their compatibility with observational data within the Starobinsky f(R) model.

Findings

Starobinsky model is consistent with observations at 2σ confidence level.

All three growth index parametrizations fit the data only at 2σ, not 1σ.

Constraints on the model parameters are derived from growth factor data.

Abstract

The growth of matter perturbations in the $f(R)$ model proposed by Starobinsky is studied in this paper. Three different parametric forms of the growth index are considered respectively and constraints on the model are obtained at both the $1\sigma$ and $2\sigma$ confidence levels, by using the current observational data for the growth factor. It is found, for all the three parametric forms of the growth index examined, that the Starobinsky model is consistent with the observations only at the $2\sigma$ confidence level.