Cosmological density perturbations in modified gravity theories
Abstract
In the context of f(R) theories of gravity, we study the cosmological evolution of scalar perturbations by using a completely general procedure. We find that the exact fourth-order differential equation for the matter density perturbations in the longitudinal gauge, reduces to a second-order equation for sub-Hubble modes. This simplification is compared with the standard (quasi-static) equation used in the literature. We show that for general f(R) functions the quasi-static approximation is not justified. However for those f(R) adequately describing the present phase of accelerated expansion and satisfying local gravity tests, it does give a correct description for the evolution of perturbations.
Cite
@article{arxiv.0812.3048,
title = {Cosmological density perturbations in modified gravity theories},
author = {A. de la Cruz-Dombriz and A. Dobado and A. L. Maroto},
journal= {arXiv preprint arXiv:0812.3048},
year = {2015}
}
Comments
4 pages, 2 figures. Contribution to the proceedings of Spanish Relativity Meeting 2008, Salamanca, Spain, 15-19 September 2008