Date Published:

April 1, 2014

Abstract:

We use the observed anisotropic clustering of galaxies in the BaryonOscillation Spectroscopic Survey Data Release 11 CMASS sample to measurethe linear growth rate of structure, the Hubble expansion rate and thecomoving distance scale. Our sample covers 8498 deg² andencloses an effective volume of 6 Gpc³ at an effectiveredshift of bar{z} = 0.57. We find fσ₈ = 0.441 ±0.044, H = 93.1 ± 3.0 km s^-1 Mpc^-1 andD_A = 1380 ± 23 Mpc when fitting the growth andexpansion rate simultaneously. When we fix the background expansion tothe one predicted by spatially flat Λ cold dark matter(ΛCDM) model in agreement with recent Planck results, we findfσ₈ = 0.447 ± 0.028 (6 per cent accuracy). Whileour measurements are generally consistent with the predictions ofΛCDM and general relativity, they mildly favour models in whichthe strength of gravitational interactions is weaker than what ispredicted by general relativity. Combining our measurements with recentcosmic microwave background data results in tight constraints on basiccosmological parameters and deviations from the standard cosmologicalmodel. Separately varying these parameters, we find w = -0.983 ±0.075 (8 per cent accuracy) and γ = 0.69 ± 0.11 (16 percent accuracy) for the effective equation of state of dark energy andthe growth rate index, respectively. Both constraints are in goodagreement with the standard model values of w = -1 and γ = 0.554.

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