用宇宙声波检验宇宙学
Testing Cosmology with Cosmic Sound Waves
摘要：
WMAP的观测准确地确定了CMB温度功率谱中前两个峰和谷的位置。这些编码信息的比例的距离最后的散射表面的声音地平线在去耦。然而，预重组过程会污染该距离信息。为了评估这些影响的幅度，我们使用WMAP数据和评估CMB峰和谷多极的相对差异。我们发现，第一个峰值的位置在很大程度上是位移相对于预期的位置的声音地平线尺度去耦。与此相反，较高的极值的相对间距是统计上一致的，从完美的谐波振荡的预期。这为CMB振荡的尺度相关相移提供了证据，该相移是由影响复合前声波传播的引力驱动力引起的。通过考虑这些影响，我们进行了MCMC似然分析，结合最近的BAO数据来约束恒定的暗能量方程w。对于一个平坦的宇宙，我们发现在95%的上限w<-1.10，包括HST先验w<-1.14，这与超新星SNLS样本得出的极限仅略微一致。对于非平坦宇宙学，得到了更大的极限。从完整的CMB似然分析中，我们还估计了几种宇宙学在解耦时的声视界的移位参数R和多极l_a的值，以测试它们对模型假设的依赖性。尽管应始终优先分析完整CMB光谱，但使用CMB峰和谷的位置提供了一种简单且一致的方法，用于将CMB约束与其他数据集相结合。
英文摘要：
WMAP observations have accurately determined the position of the first two peaks and dips in the CMB temperature power spectrum. These encode information on the ratio of the distance to the last scattering surface to the sound horizon at decoupling. However pre-recombination processes can contaminate this distance information. In order to assess the amplitude of these effects we use the WMAP data and evaluate the relative differences of the CMB peaks and dips multipoles. We find that the position of the first peak is largely displaced with the respect to the expected position of the sound horizon scale at decoupling. In contrast the relative spacings of the higher extrema are statistically consistent with those expected from perfect harmonic oscillations. This provides evidence for a scale dependent phase shift of the CMB oscillations which is caused by gravitational driving forces affecting the propagation of sound waves before recombination. By accounting for these effects we have performed a MCMC likelihood analysis to constrain in combination with recent BAO data a constant dark energy equation w. For a flat universe we find at 95% upper limit w<-1.10, and including the HST prior w<-1.14, which are only marginally consistent with limits derived from the supernova SNLS sample. Larger limits are obtained for non-flat cosmologies. From the full CMB likelihood analysis we also estimate the values of the shift parameter R and the multipole l_a of the acoustic horizon at decoupling for several cosmologies to test their dependence on model assumptions. Although the analysis of the full CMB spectra should be always preferred, using the position of the CMB peaks and dips provide a simple and consistent method for combining CMB constraints with other datasets.
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