Bianchi model CMB polarization and its implications for CMB anomalies
Bianchi model CMB polarization and its implications for CMB anomalies
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DOI：
10.1111/j.1365-2966.2007.12221.x
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发表时间：
2007-06
影响因子：
4.8
通讯作者：
A. Pontzen;A. R. I. Cambridge;Damtp Cambridge
中科院分区：
文献类型：
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作者：
A. Pontzen;A. R. I. Cambridge;Damtp Cambridge
我们推导出宇宙微波背景(CMB)辐射传输方程的形式，在近似Friedmann-Robertson-Walker极限的均匀但各向异性的宇宙中，以多极层次的形式按Bianci类型分类。与以前的计算相比，这允许对复合进行更复杂的处理，产生对辐射偏振的预测，并允许重新电离。我们的推导与对场方程的动力学行为的任何假设无关，只是它要求各向异性小到复合；这已经是观察所要求的。我们计算了比安奇VIIh情况下的偏振信号，用最近提出的参数来模拟在CMB中观察到的几个大角度反常特征。我们发现，与温度各向异性最匹配的模型的峰值偏振信号为∼1.2μK，并且大部分被限制在多极子L和10。值得注意的是，在比安奇模型中预测的大角度EE和TE功率谱与通常被解释为早期再电离证据的威尔金森微波各向异性探测器观测相一致。然而，B模偏振的功率被预测为类似于E模的功率，该模型还预测了宇称破坏关联；这些信号的WMAP未被检测到进一步对试图解释具有全局各向异性的大角度异常的准确性提出了强烈的怀疑。另一方面，考虑到VIIH宇宙中还有更多的动力学自由度尚未与CMB观测进行比较，我们目前还不能断然拒绝各向异性的解释。
We derive the cosmic microwave background (CMB) radiative transfer equation in the form of a multipole hierarchy in the nearly Friedmann–Robertson–Walker limit of homogeneous, but anisotropic, universes classified via their Bianchi type. Compared with previous calculations, this allows a more sophisticated treatment of recombination, produces predictions for the polarization of the radiation and allows for reionization. Our derivation is independent of any assumptions about the dynamical behaviour of the field equations, except that it requires anisotropies to be small back to recombination; this is already demanded by observations. We calculate the polarization signal in the Bianchi VIIh case, with the parameters recently advocated to mimic the several large-angle anomalous features observed in the CMB. We find that the peak polarization signal is ∼1.2 μK for the best-fitting model to the temperature anisotropies, and is mostly confined to multipoles l < 10. Remarkably, the predicted large-angle EE and TE power spectra in the Bianchi model are consistent with Wilkinson Microwave Anisotropy Probe (WMAP) observations that are usually interpreted as evidence of early reionization. However, the power in B-mode polarization is predicted to be similar to the E-mode power and parity-violating correlations are also predicted by the model; the WMAP non-detection of either of these signals casts further strong doubts on the veracity of attempts to explain the large-angle anomalies with global anisotropy. On the other hand, given that there exist further dynamical degrees of freedom in the VIIh universes that are yet to be compared with CMB observations, we cannot at this time definitively reject the anisotropy explanation.