Probing modifications of general relativity using current cosmological observations

Citation Zhao, Gong-Bo et al. " Probing modifications of general relativity using current cosmological observations. Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. We test general relativity (GR) using current cosmological data: the CMB from WMAP5 [E. Komatsu et al.] that probe linear and mildly nonlinear scales. We first test a model in which the effective Newtonian constant and the ratio of the two gravitational potentials, , transit from the GR value to another constant at late times; in this case, we find that GR is fully consistent with the combined data. The strongest constraint comes from the ISW effect which would arise from this gravitational transition; the observed ISW signal imposes a tight constraint on a combination of and that characterizes the lensing potential. Next, we consider four pixels in time and space for each function and , and perform a principal component analysis, finding that seven of the resulting eight eigenmodes are consistent with GR within the errors. Only one eigenmode shows a 2 deviation from the GR prediction, which is likely to be due to a systematic effect. However, the detection of such a deviation demonstrates the power of our time-and scale-dependent principal component analysis methodology when combining observations of structure formation and expansion history to test GR.