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arXiv 2005.10250astro-ph.CO
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宇宙学21厘米圆极化的标准模型预测

Standard Model Prediction for Cosmological 21cm Circular Polarization

Lingyuan Ji, Marc Kamionkowski, Keisuke Inomata

摘要:

在宇宙再电离之前,氢原子通过与各向异性21厘米辐射场的相互作用获得自旋极化四极。在宇宙微波背景(CMB)辐射场中,这种四极子与各向异性的相互作用使氢原子产生净自旋取向。这些自旋取向的氢原子发射的21厘米辐射是圆偏振的。在这里,我们重新简洁地推导出笛卡尔(而不是球面)张量的圆偏振的表达式。然后,我们计算了观测到的Stokes- $V$参数在标准$Λ$ CDM宇宙学模型的角功率谱,并显示它如何依赖于红移,或等价地,观测到的频率。

英文摘要:

Before cosmic reionization, hydrogen atoms acquire a spin polarization quadrupole through interaction with the anisotropic 21-cm radiation field. The interaction of this quadrupole with anisotropies in the cosmic microwave background (CMB) radiation field gives a net spin orientation to the hydrogen atoms. The 21-cm radiation emitted by these spin-oriented hydrogen atoms is circularly polarized. Here, we reformulate succinctly the derivation of the expression for this circular polarization in terms of Cartesian (rather than spherical) tensors. We then compute the angular power spectrum of the observed Stokes-$V$ parameter in the standard $Λ$CDM cosmological model and show how it depends on redshift, or equivalently, the observed frequency.

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