Cosmological Perturbations in f(R) Gravity
Gu, Je-An (LeCosPA Center, National Taiwan University)

We investigate the evolution of the cosmological perturbations in f(R) gravity, an alternative of dark energy. In many cases one invokes approximated evolution equations, e.g., those in general relativity for the early times and those with the sub-horizon and matter-dominated approximations for the late times. We examine the validity of these approximations and develop a new method for calculating the evolution of the perturbed quantities, in particular the matter density perturbation and the metric perturbations.