Characterizing the linear growth rate of cosmological density perturbations in an f(R) model

We investigate the linear growth rate of cosmological matter density perturbations in a viable f(R) model both numerically and analytically. We find that the growth rate in the scalar-tensor regime can be characterized by a simple analytic formula. We also investigate a prospect of constraining the Compton wavelength scale of the f(R) model with a future weak lensing survey.