PostNewtonian constraints on f(R) cosmologies in Palatini formalism
Abstract
We compute the complete postNewtonian limit of the Palatini form of f(R) gravities using a scalartensor representation. By comparing the predictions of these theories with laboratory and solar system experiments, we find a set of inequalities that any lagrangian f(R) must satisfy. The constraints imposed by those inequalities allow us to find explicit functions that bound from above and from below the possible nonlinear terms of the lagrangian. We conclude that the lagrangian f(R) must be almost linear in R and that nonlinear corrections that grow at low curvatures are incompatible with observations. This result shows that modifications of gravity at very low cosmic densities cannot be responsible for the observed cosmic speedup.
 Publication:

arXiv eprints
 Pub Date:
 May 2005
 DOI:
 10.48550/arXiv.grqc/0505136
 arXiv:
 arXiv:grqc/0505136
 Bibcode:
 2005gr.qc.....5136O
 Keywords:

 Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 8 pages, no figures