Jason Dossett, Mustapha Ishak
It is well known that allowing for spatial curvature affects constraints on cosmological parameters such as the dark energy equation of state parameters. Here we study the effect of curvature on constraints on parameters used to test General Relativity (GR) at cosmological scales, commonly known as modified growth (MG) parameters. Using the latest cosmological data sets we find that MG parameters are correlated with the curvature parameter $\Omega_k$ and the constraints on the MG parameters are weakened compared to when $\Omega_k$ is not included in the parameter analysis. We next use various future simulated data sets including, cosmic microwave background, weak lensing, and ISW-galaxy cross correlations, where the fiducial model is spatially curved but we assume a flat model when fitting the MG parameters. We find the assumption of a spatially flat model on a spatially curved universe does indeed cause an artificial shift in the constraints on the MG parameters, in some cases even producing an apparent deviation from GR in the MG parameter space. The apparent deviations from GR manifest themselves for fiducial models with $\abs{\Omega_k} \geq 0.02$ and the shift in the parameter space is produced even for smaller values of spatial curvature. We find that for negatively curved models the apparent deviation is more significant. The manifestation of this apparent deviation from GR due to the assumption of spatial flatness above leads one to conclude that, when using future high precision data to perform these tests, spatial curvature must be included in the parameter analysis along with the other core cosmological parameters and the MG parameters.
View original:
http://arxiv.org/abs/1205.2422
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