Structure formation in modified gravity

We pursue a (l+3)-covariant analysis of cosmological peculiar velocity of pressure-free matter induced by the matter density perturbations in modified f(R) gravity theories. Instead of working in a quasi-Newtonian Eulerian frame, we select a curvature comoving Lagrangian frame, which means the shear and heat energy flux are non-zero. This is part of ongoing work on the end-structure of a generic over-density in f(R) gravity. © 2009 American Institute of Physics.