Title: Probing modifications of General Relativity using current cosmological observations Show Chinese title

Title: 利用当前宇宙学观测探测广义相对论的修改

Abstract: We test General Relativity (GR) using current cosmological data: the cosmic microwave background (CMB) from WMAP5 (Komatsu et al. 2009), the integrated Sachs-Wolfe (ISW) effect from the cross-correlation of the CMB with six galaxy catalogs (Giannantonio et al. 2008), a compilation of supernovae Type Ia (SNe) including the latest SDSS SNe (Kessler et al. 2009), and part of the weak lensing (WL) data from CFHTLS (Fu et al. 2008, Kilbinger et al. 2009) that probe linear and mildly non-linear scales. We first test a model where the effective Newton's constant, mu, and the ratio of the two gravitational potentials, 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 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 mu and eta that characterizes the lensing potential. Next, we consider four pixels in time and space for each function mu and eta, and perform a Principal Component Analysis (PCA) finding that seven of the resulting eight eigenmodes are consistent with GR within the errors. Only one eigenmode shows a 2-sigma 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 PCA methodology when combining observations of structure formation and expansion history to test GR. Show Chinese abstract

Abstract: 我们利用当前的宇宙学数据检验广义相对论（GR）：来自WMAP5（Komatsu等，2009年）的宇宙微波背景（CMB），由CMB与六个星系目录的交叉相关性得到的积分萨克斯-沃尔夫（ISW）效应（Giannantonio等，2008年），包括最新SDSS超新星Ia（SNe）的数据集（Kessler等，2009年），以及来自CFHTLS的弱透镜（WL）数据的一部分（Fu等，2008年；Kilbinger等，2009年），这些数据探测了线性和轻微非线性尺度。 我们首先测试了一种模型，在这种模型中，有效的牛顿常数μ和两个引力势的比值η在晚期从GR值过渡到另一个常数值；在这种情况下，我们发现标准GR完全与组合数据一致。 最强的约束来自这种引力转变引起的ISW效应；观测到的ISW信号对表征透镜势的μ和η的组合施加了一个严格的限制。 接下来，我们为每个函数μ和η考虑四个时空像素，并执行主成分分析（PCA），发现八个特征模态中有七个在误差范围内与GR一致。 只有一个特征模态显示出2σ的偏离，这很可能是由于系统效应。 然而，这种偏离的检测展示了我们在结合结构形成和膨胀历史观测来检验GR时的时间和尺度依赖性PCA方法的强大功能。