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: 我们使用当前的宇宙学数据来检验广义相对论（GR）：来自WMAP5（Komatsu等，2009）的宇宙微波背景（CMB），来自CMB与六个星系目录交叉相关性的积分萨克斯-沃尔夫（ISW）效应（Giannantonio等，2008），包括最新SDSS超新星（SNe）的Ia型超新星（SNe）汇编（Kessler等，2009），以及来自CFHTLS（Fu等，2008，Kilbinger等，2009）的部分弱透镜（WL）数据，这些数据探测线性和轻微非线性尺度。我们首先测试一个模型，其中有效牛顿常数mu和两个引力势的比值eta在晚期时间从GR值过渡到另一个常数；在这种情况下，我们发现标准GR与综合数据完全一致。最强的约束来自由此引力过渡产生的ISW效应；观测到的ISW信号对一个描述透镜势的mu和eta的组合施加了严格的限制。接下来，我们为每个函数mu和eta考虑时间和空间中的四个像素，并进行主成分分析（PCA），发现八个特征模式中有七个在误差范围内与GR一致。只有一个特征模式显示出与GR预测的2倍标准差偏差，这可能是由于系统效应所致。然而，检测到这种偏差证明了我们的时空依赖PCA方法在结合结构形成和膨胀历史观测数据来检验GR时的强大能力。