N ov 2 00 8 Constraining Post - Newtonian f ( R ) Gravity in the Solar System Matteo Luca Ruggiero

We consider some models of f(R) gravity that can be used to describe, in a suitable weak-field limit, the gravitational field of the Sun. Using a perturbative approach, we focus on the impact that the modifications of the gravitational field, due to the non-linearity of the gravity Lagrangian, have on the Solar System dynamics. We compare the theoretical predictions for the precession of the longitude of the pericentre ̟ of a test particle with the corrections to the standard Newtonian-Einsteinian precessions of the longitudes of perihelia of some planets of the Solar System recently estimated by E.V. Pitjeva by fitting large data sets with various versions of the EPM ephemerides. Subject headings: Experimental tests of gravitational theories; Modified theories of gravity; Celestial mechanics; Orbit determination and improvement; Ephemerides, almanacs, and calendars