宇宙微波背景声峰位置
Cosmic Microwave Background Acoustic Peak Locations
摘要：
普朗克合作测量了宇宙微波背景的温度和极化，足以确定温度（TT）功率谱中的八个峰，极化（EE）功率谱中的五个峰和交叉（TE）功率谱中的十二个极值的位置。这些极值的相对位置给出了一个惊人的，美丽的，我们期望从等离子体中的声振荡演示;例如，EE峰落在TT峰之间的一半。我们预期这是因为温度图主要来源于最后散射表面的温度变化，而偏振图主要来源于速度场的梯度，并且谐波振荡具有90度的温度和速度相位差。然而，从简单的分析模型与数值计算的极值位置的期望有很大的差异。在这里，我们定量地探讨这些差异的起源在引力势瞬变，中微子自由流，紧耦合的崩溃，原始功率谱的形状，从三维到二维的几何投影的细节，以及最后散射表面的厚度。我们还比较了峰值位置从普朗克测量的期望下的$Λ$ CDM模型。考虑到峰值位置是如何确定的，我们发现它们是一致的。
英文摘要：
The Planck collaboration has measured the temperature and polarization of the cosmic microwave background well enough to determine the locations of eight peaks in the temperature (TT) power spectrum, five peaks in the polarization (EE) power spectrum and twelve extrema in the cross (TE) power spectrum. The relative locations of these extrema give a striking, and beautiful, demonstration of what we expect from acoustic oscillations in the plasma; e.g., that EE peaks fall half way between TT peaks. We expect this because the temperature map is predominantly sourced by temperature variations in the last scattering surface, while the polarization map is predominantly sourced by gradients in the velocity field, and the harmonic oscillations have temperature and velocity 90 degrees out of phase. However, there are large differences in expectations for extrema locations from simple analytic models vs. numerical calculations. Here we quantitatively explore the origin of these differences in gravitational potential transients, neutrino free-streaming, the breakdown of tight coupling, the shape of the primordial power spectrum, details of the geometric projection from three to two dimensions, and the thickness of the last scattering surface. We also compare the peak locations determined from Planck measurements to expectations under the $Λ$CDM model. Taking into account how the peak locations were determined, we find them to be in agreement.
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