f(R) Gravity and Chameleon Theories

Abstract

We analyse f(R) modifications of Einstein's gravity as dark energy models in the light of their connection with chameleon theories. Formulated as scalar-tensor theories, the f(R) theories imply the existence of a strong coupling of the scalar field to matter. This would violate all experimental gravitational tests on deviations from Newton's law. Fortunately, the existence of a matter dependent mass and a thin shell effect allows one to alleviate these constraints. The thin shell condition also implies strong restrictions on the cosmological dynamics of the f(R) theories. As a consequence, we find that the equation of state of dark energy is constrained to be extremely close to -1 in the recent past. We also examine the potential effects of f(R) theories in the context of the Eot-wash experiments. We show that the requirement of a thin shell for the test bodies is not enough to guarantee a null result on deviations from Newton's law. As long as dark energy accounts for a sizeable fraction of the total energy density of the Universe, the constraints which we deduce also forbid any measurable deviation of the dark energy equation of state from -1. All in all, we find that both cosmological and laboratory tests imply that f(R) models are almost coincident with a Lambda-CDM model at the background level.

18 pages, 5 figures

References in corpus (13)

• Models of f(R) Cosmic Acceleration that Evade Solar-System Tests
• Observational Constraints on the Nature of the Dark Energy: First Cosmological Results from the ESSENCE Supernova Survey
• A Parameterized Post-Friedmann Framework for Modified Gravity
• Constraining f(R) Gravity as a Scalar Tensor Theory
• The Cosmology of f(R) Gravity in the Metric Variational Approach
• Dark Energy and Dark Gravity
• Constraints on scalar-tensor models of dark energy from observational and local gravity tests
• Cosmological Constraints on f(R) Acceleration Models
• Compatibility of the chameleon-field model with fifth-force experiments, cosmology, and PVLAS and CAST results
• Detecting Chameleons through Casimir Force Measurements
• Next Generation Redshift Surveys and the Origin of Cosmic Acceleration
• Testing Chameleon Theories with Light Propagating through a Magnetic Field
• How (Not) to Palatini

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• Detecting Chameleons: The Astronomical Polarization Produced by Chameleon-like Scalar Fields
• Comments on Scalar-Tensor Representation of $f(R)$ Theories