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f(R) gravity and chameleon theories

Brax, P., van de Bruck, C., Davis, A.C. and Shaw, D.J. (2008) f(R) gravity and chameleon theories. Physical Review D, 79 (10). Art. No. 104021. ISSN 1550-2368

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We analyze 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 Eöt-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 that 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 ΛCDM model at the background level.

Item Type: Article
Copyright, Publisher and Additional Information: © 2008 The American Physical Society. This is an author produced version of a paper subsequently published in 'Physical Review D.' Uploaded in accordance with the publisher's self-archiving policy.
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > School of Mathematics and Statistics (Sheffield)
Depositing User: Mrs Megan Hobbs
Date Deposited: 24 Mar 2010 15:29
Last Modified: 17 Nov 2015 02:26
Published Version: http://dx.doi.org/10.1103/PhysRevD.78.104021
Status: Published
Publisher: American Physical Society
Refereed: No
Identification Number: 10.1103/PhysRevD.78.104021
Related URLs:
URI: http://eprints.whiterose.ac.uk/id/eprint/10571

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