We test General Relativity (GR) using current cosmological data: the cosmicmicrowave background (CMB) from WMAP5 (Komatsu et al. 2009), the integratedSachs-Wolfe (ISW) effect from the cross-correlation of the CMB with six galaxycatalogs (Giannantonio et al. 2008), a compilation of supernovae Type Ia (SNe)including the latest SDSS SNe (Kessler et al. 2009), and part of the weaklensing (WL) data from CFHTLS (Fu et al. 2008, Kilbinger et al. 2009) thatprobe linear and mildly non-linear scales. We first test a model where theeffective Newton's constant, mu, and the ratio of the two gravitationalpotentials, eta, transit from the GR value to another constant at late times;in this case, we find that standard GR is fully consistent with the combineddata. The strongest constraint comes from the ISW effect which would arise fromthis gravitational transition; the observed ISW signal imposes a tightconstraint on a combination of mu and eta that characterizes the lensingpotential. Next, we consider four pixels in time and space for each function muand eta, and perform a Principal Component Analysis (PCA) finding that seven ofthe resulting eight eigenmodes are consistent with GR within the errors. Onlyone eigenmode shows a 2-sigma deviation from the GR prediction, which is likelyto be due to a systematic effect. However, the detection of such a deviationdemonstrates the power of our time- and scale-dependent PCA methodology whencombining observations of structure formation and expansion history to test GR.
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