Magnetic Field Spectrum at Cosmological Recombination Revisited
Magnetic Field Spectrum at Cosmological Recombination Revisited
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重新审视宇宙重组时的磁场谱
DOI：
10.1103/physrevd.91.123510
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发表时间：
2015
影响因子：
5
通讯作者：
Keitaro Takahashi and Naoshi Sugiyama
中科院分区：
文献类型：
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作者：
Shohei Saga;Kiyotomo Ichiki;Keitaro Takahashi and Naoshi Sugiyama
如果矢量型扰动存在于复合前的原始等离子体中，则通过哈里森机制，磁场的产生是不可避免的。在标准宇宙学微扰理论中，一阶标量微扰的非线性耦合产生二阶矢量微扰，从而产生磁场。本文在前人研究的基础上，重新研究了二阶磁场在宇宙学微扰中的产生，并通过新开发的二阶Boltzmann码考虑了纯二阶矢量微扰的时间演化，对二阶磁场的产生进行了扩展。我们证实了由一阶标量模的乘积项得到的磁场振幅与我们以前的研究结果是一致的。然而，我们发现，无论是数值和分析，从纯粹的二阶矢量扰动的磁场部分抵消了磁场的一阶标量模式的产品项之一，在紧耦合制度中的辐射占主导地位的时代。因此，小尺度上的磁场振幅小于先前的估计。在宇宙学复合中产生的磁场的振幅约为。最后，我们讨论了其他作者之间的磁场的振幅的估计存在差异的原因。
If vector type perturbations are present in the primordial plasma before recombination, the generation of magnetic fields is known to be inevitable through the Harrison mechanism. In the context of the standard cosmological perturbation theory, nonlinear couplings of first-order scalar perturbations create second-order vector perturbations, which generate magnetic fields. Here we reinvestigate the generation of magnetic fields at second-order in cosmological perturbations on the basis of our previous study, and extend it by newly taking into account the time evolution of purely second-order vector perturbations with a newly developed second-order Boltzmann code. We confirm that the amplitude of magnetic fields from the product-terms of the first-order scalar modes is consistent with the result in our previous study. However, we find, both numerically and analytically, that the magnetic fields from the purely second-order vector perturbations partially cancel out the magnetic fields from one of the product-terms of the first-order scalar modes, in the tight coupling regime in the radiation dominated era. Therefore, the amplitude of the magnetic fields on small scales,, is smaller than the previous estimates. The amplitude of the generated magnetic fields at cosmological recombination is abouton. Finally, we discuss the reason for the discrepancies that exist in estimates of the amplitude of magnetic fields among other authors.