Palatini f (R) gravity in the solar system : post-Newtonian equations of motion and complete PPN parameters.

Abstract

We perform a post-Newtonian (PN) solar system analysis for Palatini fðRÞ theories considering finite volume nonspherical planets and with emphasis to fðRÞ functions that are analytical about R 1⁄4 0. First we consider the Will-Nordtvedt parametrized post-Newtonian (PPN) formalism, from which the metric is shown to depend, in general, on terms not covered by the standard PPN potentials. Hence, a full analysis of the PN equations of motion is performed. From the latter we conclude that, apart from redefinitions on the internal energy and the pressure, which cannot be constrained by solar system tests, the center-of-mass orbits are the same as in general relativity. We discuss further the physics of these redefinitions and use an argument to extend our analytical fðRÞ results towards some nonanalytical functions.