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: 我们利用最新的宇宙微波背景数据（包括威尔金森微波各向异性探测器（WMAP）的新结果）以及来自二维场星系红移巡天（2dFGRS）的大尺度结构数据，重构了原始功率谱的形状。我们测试了四种参数化方法，考虑了四个宇宙学参数的不确定性。 首先，我们将初始谱参数化为倾斜和运行光谱指数，并发现仅当分析中包含前三个 WMAP 多极值（l=2,3,4）时，才有边际证据表明存在运行光谱指数。 其次，为了进一步研究低频 CMB 的大尺度功率，我们在传统幂律谱的基础上引入了一个高于该尺度没有功率的截断。我们发现截断位置更倾向于 kc ~ 3e-4 /Mpc，尽管 kc=0（无截断）并未被排除。 第三，我们使用了一种模型无关的参数化方法，在波数上有 16 个区间，并未发现明显偏离幂律谱的迹象。此外，尽管初始功率谱形状具有自由度，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模型启发的模型，其中功率谱在两个特征波数之间有一个转折点。我们发现如果转折点需要位于 0.01 < k Mpc < 0.1 范围内，则转折点两侧幅度比被限制为 1.23 +/- 0.14。 我们的结果与一个在波数范围 0.005 ~< k Mpc ~< 0.15 内接近标度不变且无特征的幂律谱一致，但暗示最大尺度上功率有轻微下降。