f(R) gravity and chameleon theories

By P. Brax, C. Bruck, A. Davis, D. Shaw. 2008

244 citations recorded by the source corpus.

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 Eoet-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 testsmore » imply that f(R) models are almost coincident with a {lambda}CDM model at the background level.« less

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/57226fb7a2cf023e8d0655fc398e81437d721797

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Citations in the corpus

f(R) Theories (2010, background): “The effect of the chameleon mechanism [344, 343] becomes important in this nonlinear regime (δR≫ R0) [251, 306, 134, 101].”
Beyond the Cosmological Standard Model (2014, unknown): “Various considerations constrain the functional form of the potential V (φ) and the coupling function A(φ) [184, 185, 247, 274]:16 • In order to have interesting effects, we want to balance the two contributions to the effective potential in (5.”
Accurate halo-model matter power spectra with dark energy, massive neutrinos and modified gravitational forces (2016, background): “It was shown that f (R) models can exhibit the chameleon mechanism by Li & Barrow (2007), Hu & Sawicki (2007b) and Brax et al. (2008).”
Equivalence Principle Implications of Modified Gravity Models (2009, background): “Indeed, neither theory is completely satisfactory: acceptable f(R) models accelerate the universe mostly by a cosmological constant rather than by a genuine modified gravity effect [26]; also from an effective field theory standpoint they are not favored in any sense over more general scalar-tensor ”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, background): “We mention here only that the presence of chameleon mechanisms [234, 887, 885, 235, 621, 236, 380] can, for example, modify the coupling depending on the environment.”
Modified Gravity and Cosmology (2011, unknown): “[237] [867] [1084] [452] [174] [1101] [217] [576].”