Primordial magnetic fields from self-ordering scalar fields
Primordial magnetic fields from self-ordering scalar fields
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来自自序标量场的原始磁场
DOI：
10.1088/1475-7516/2015/04/007
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发表时间：
2015
影响因子：
6.4
通讯作者：
Naoshi Sugiyama
中科院分区：
文献类型：
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作者：
Kouichirou Horiguchi;Kiyotomo Ichiki;Toyokazu Sekiguchi;Naoshi Sugiyama
早期宇宙中一个破坏对称的相变可能导致了宇宙缺陷的形成。由于这些缺陷不仅能动态激发标量型和张量型宇宙学扰动，而且还能激发矢量型宇宙学扰动，因此它们可能是原始磁场的来源。在这项研究中，我们使用非线性西格玛（NLSM）模型计算了由一种称为全局纹理的宇宙缺陷产生的磁场的时间演化和频谱。基于标准的宇宙学摄动理论，我们用解析和数值两种方法证明了光子和重子流体之间的矢量模相对速度是由织构引起的，这不可避免地导致了大范围磁场的产生。我们发现，在k > 1 Mpc−1的辐射主导时代，磁场的振幅为B ~ 10−9 ((1+ z)/10 3)−2.5 (v/m pl) 2 (k/Mpc−1)3.5/√N高斯，其中v为O (N)对称标量场的真空期望值。通过将我们的数值结果外推到更小的尺度上，我们预计在红移为0z约110的k≤1mpc−1的尺度上，B ~ 10−14.5 ((1+ z)/ 10.3) 1/2 (v/m pl) 2 (k/Mpc−1)1/2/√N高斯。这可能是今天在大尺度上观测到的磁场的种子。
A symmetry-breaking phase transition in the early universe could have led to the formation of cosmic defects. Because these defects dynamically excite not only scalar and tensor type cosmological perturbations but also vector type ones, they may serve as a source of primordial magnetic fields. In this study, we calculate the time evolution and the spectrum of magnetic fields that are generated by a type of cosmic defects, called global textures, using the non-linear sigma (NLSM) model. Based on the standard cosmological perturbation theory, we show, both analytically and numerically, that a vector-mode relative velocity between photon and baryon fluids is induced by textures, which inevitably leads to the generation of magnetic fields over a wide range of scales. We find that the amplitude of the magnetic fields is given by B∼ 10− 9 ((1+ z)/10 3)− 2.5 (v/m pl) 2 (k/Mpc− 1) 3.5/√ N Gauss in the radiation dominated era for k≲ 1 Mpc− 1, with v being the vacuum expectation value of the O (N) symmetric scalar fields. By extrapolating our numerical result toward smaller scales, we expect that B∼ 10− 14.5 ((1+ z)/10 3) 1/2 (v/m pl) 2 (k/Mpc− 1) 1/2/√ N Gauss on scales of k≳ 1 Mpc− 1 at redshift 0z≳ 110. This might be a seed of the magnetic fields observed on large scales today.