标题： 宇宙磁场螺旋性对宇宙微波背景的影响 显示英文标题

标题： Effects of Cosmological Magnetic Helicity on the Cosmic Microwave Background

摘要： 宇宙磁场会在宇宙微波背景（CMB）辐射的温度和极化涨落下诱导出波动。具有当前幅值约为$10^{-9}$G 的宇宙磁场可通过观测 CMB 各向异性来检测到。这种磁场（有旋或无旋）通过原始等离子体的涡流运动生成矢量扰动。本文表明磁场的有旋性会在 CMB 温度和$B$极化涨落之间以及$E$和$B$极化涨落之间诱导出奇偶不对称的交叉关联，而对于无旋场（或任何奇偶不变源），这些关联为零。有旋场还对奇偶偶性的温度和极化各向异性作出贡献，部分抵消了磁场对称分量的贡献。我们给出了由有旋磁场引起的所有 CMB 温度和极化各向异性矢量功率谱的解析近似。这些功率谱提供了一种探测宇宙有旋磁场的方法，特别是当与对有旋性不敏感的法拉第旋转测量结合使用时。 显示英文摘要

摘要： Cosmological magnetic fields induce temperature and polarization fluctuations in the cosmic microwave background (CMB) radiation. A cosmological magnetic field with current amplitude of order $10^{-9}$ G is detectable via observations of CMB anisotropies. This magnetic field (with or without helicity) generates vector perturbations through vortical motions of the primordial plasma. This paper shows that magnetic field helicity induces parity-odd cross correlations between CMB temperature and $B$-polarization fluctuations and between $E$- and $B$-polarization fluctuations, correlations which are zero for fields with no helicity (or for any parity-invariant source). Helical fields also contribute to parity-even temperature and polarization anisotropies, cancelling part of the contribution from the symmetric component of the magnetic field. We give analytic approximations for all CMB temperature and polarization anisotropy vector power spectra due to helical magnetic fields. These power spectra offer a method for detecting cosmological helical magnetic fields, particularly when combined with Faraday rotation measurements which are insensitive to helicity.