Title: Reconstructing the primordial power spectrum Show Chinese title

Title: 重建原始功率谱

Abstract: We reconstruct the shape of the primordial power spectrum from the latest cosmic microwave background data, including the new results from the Wilkinson Microwave Anisotropy Probe (WMAP), and large scale structure data from the two degree field galaxy redshift survey (2dFGRS). We tested four parameterizations taking into account the uncertainties in four cosmological parameters. First we parameterize the initial spectrum by a tilt and a running spectral index, finding marginal evidence for a running spectral index only if the first three WMAP multipoles (ell=2,3,4) are included in the analysis. Secondly, to investigate further the low CMB large scale power, we modify the conventional power-law spectrum by introducing a scale above which there is no power. We find a preferred position of the cut at k_c ~ 3e-4 /Mpc although k_c=0 (no cut) is not ruled out. Thirdly we use a model independent parameterization, with 16 bands in wavenumber, and find no obvious sign of deviation from a power law spectrum on the scales investigated. Furthermore the values of the other cosmological parameters defining the model remain relatively well constrained despite the freedom in the shape of the initial power spectrum. Finally we investigate a model motivated by double inflation, in which the power spectrum has a break between two characteristic wavenumbers. We find that if a break is required to be in the range 0.01 < k Mpc <0.1 then the ratio of amplitudes across the break is constrained to be 1.23 +/- 0.14. Our results are consistent with a power law spectrum that is featureless and close to scale invariant over the wavenumber range 0.005 ~< k Mpc ~< 0.15, with a hint of a decrease in power on the largest scales. Show Chinese abstract

Abstract: 我们从最新的宇宙微波背景数据中重建了原初功率谱的形状，包括威尔金森微波各向异性探测器（WMAP）的新结果，以及二维场星系红移巡天（2dFGRS）的大尺度结构数据。 我们测试了四种参数化方法，考虑到四个宇宙学参数的不确定性。 首先，我们通过倾斜和运行光谱指数对初始谱进行参数化，发现只有在分析中包含前三个WMAP多极矩（ell=2,3,4）时，才会有边缘证据表明存在运行光谱指数。 其次，为了进一步研究低CMB大尺度功率，我们通过引入一个没有功率的尺度来修改传统的幂律谱。 我们发现截断位置k_c ~ 3e-4 /Mpc是优选的，尽管k_c=0（无截断）并未被排除。 第三，我们使用一种与模型无关的参数化方法，在波数上分为16个区间，发现所研究尺度上没有明显的偏离幂律谱的迹象。 此外，尽管初始功率谱的形状具有自由度，但定义模型的其他宇宙学参数值仍然相对受到良好约束。 最后，我们研究了一种由双暴胀驱动的模型，其中功率谱在两个特征波数之间有一个拐点。 我们发现，如果拐点必须位于0.01 < k Mpc <0.1范围内，则拐点两侧振幅的比值被限制为1.23 +/- 0.14。 我们的结果与一个在波数范围0.005 ~< k Mpc ~< 0.15内无特征且接近尺度不变的幂律谱一致，并且在最大尺度上显示出功率下降的迹象。