We use the observed anisotropic clustering of galaxies in the Baryon Oscillation Spectroscopic Survey ( BOSS ) Data Release 11 CMASS sample to measure the linear growth rate of structure , the Hubble expansion rate and the comoving distance scale .
Our sample covers 8498 { deg } ^ { 2 } and encloses an effective volume of 6 { Gpc } ^ { 3 } at an effective redshift of \bar { z } = 0.57 .
We find f \sigma _ { 8 } = 0.441 \pm 0.044 , H = 93.1 \pm 3.0 { \mathrm { km } \mathrm { s } ^ { -1 } \mathrm { Mpc } ^ { -1 } } and D _ { A } = 1380 \pm 23 { Mpc } when fitting the growth and expansion rate simultaneously .
When we fix the background expansion to the one predicted by spatially-flat \Lambda CDM model in agreement with recent Planck results , we find f \sigma _ { 8 } = 0.447 \pm 0.028 ( 6 per cent accuracy ) .
While our measurements are generally consistent with the predictions of \Lambda CDM and General Relativity , they mildly favor models in which the strength of gravitational interactions is weaker than what is predicted by General Relativity .
Combining our measurements with recent cosmic microwave background data results in tight constraints on basic cosmological parameters and deviations from the standard cosmological model .
Separately varying these parameters , we find w = -0.983 \pm 0.075 ( 8 per cent accuracy ) and \gamma = 0.69 \pm 0.11 ( 16 per cent accuracy ) for the effective equation of state of dark energy and the growth rate index , respectively .
Both constraints are in good agreement with the standard model values of w = -1 and \gamma = 0.554 .