Cosmological Constraints on f(R) Acceleration Models

TL;DR

This paper investigates f(R) gravity models that modify cosmic acceleration, analyzing various cosmological data sets to constrain the models, especially focusing on the integrated Sachs-Wolfe effect and large-scale structure signatures.

Contribution

It provides the first comprehensive constraints on f(R) models using multiple cosmological observations, emphasizing the impact on the integrated Sachs-Wolfe effect.

Findings

Constraints on the Compton wavelength are of order the Hubble scale.

Galaxy power spectrum yields weak constraints due to nonlinear uncertainties.

Enhanced low multipole power in the CMB indicates potential signatures of f(R) models.

Abstract

Models which accelerate the expansion of the universe through the addition of a function of the Ricci scalar f(R) leave a characteristic signature in the large-scale structure of the universe at the Compton wavelength scale of the extra scalar degree of freedom. We search for such a signature in current cosmological data sets: the WMAP cosmic microwave background (CMB) power spectrum, SNLS supernovae distance measures, the SDSS luminous red galaxy power spectrum, and galaxy-CMB angular correlations. Due to theoretical uncertainties in the nonlinear evolution of f(R) models, the galaxy power spectrum conservatively yields only weak constraints on the models despite the strong predicted signature in the linear matter power spectrum. Currently the tightest constraints involve the modification to the integrated Sachs-Wolfe effect from growth of gravitational potentials during the acceleration epoch. This effect is manifest for large Compton wavelengths in enhanced low multipole power in the CMB and anti-correlation between the CMB and tracers of the potential. They place a bound on the Compton wavelength of the field be less than of order the Hubble scale.