Solar system and equivalence principle constraints on f(R) gravity by chameleon approach

TL;DR

This paper investigates constraints on f(R) gravity models from solar system and equivalence principle tests, finding tight bounds on model parameters and assessing their deviation from the standard LambdaCDM cosmology.

Contribution

It provides new experimental bounds on specific f(R) models using solar system and equivalence principle tests, highlighting their near indistinguishability from LambdaCDM.

Findings

Bound n > 0.5 from post-Newtonian gamma constraints

Bound n > 0.9 from equivalence principle violations

Model p < 10^{-10} is nearly indistinguishable from LambdaCDM

Abstract

We study constraints on f(R) dark energy models from solar system experiments combined with experiments on the violation of equivalence principle. When the mass of an equivalent scalar field degree of freedom is heavy in a region with high density, a spherically symmetric body has a thin-shell so that an effective coupling of the fifth force is suppressed through a chameleon mechanism. We place experimental bounds on the cosmologically viable models recently proposed in literature which have an asymptotic form f(R)=R-lambda R_c [1-(R_c/R)^{2n}] in the regime R >> R_c. From the solar-system constraints on the post-Newtonian parameter gamma, we derive the bound n>0.5, whereas the constraints from the violations of weak and strong equivalence principles give the bound n>0.9. This allows a possibility to find the deviation from the LambdaCDM cosmological model. For the model f(R)=R-lambda R_c(R/R_c)^p with 0<p<1 the severest constraint is found to be p<10^{-10}, which shows that this model is hardly distinguishable from the LambdaCDM cosmology.