Constraint on the primordial vector mode and its magnetic field generation from seven-year Wilkinson Microwave Anisotropy Probe observations
Constraint on the primordial vector mode and its magnetic field generation from seven-year Wilkinson Microwave Anisotropy Probe observations
复制标题
威尔金森微波各向异性探测器七年观测对原初矢量模式及其磁场产生的约束
DOI：
10.1103/physrevd.85.043009
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发表时间：
2012
影响因子：
5
通讯作者：
N.Sugiyama
中科院分区：
文献类型：
--
作者：
K.Ichiki;K.Takahashi;N.Sugiyama
通常认为宇宙学矢量模只有一个衰减模，对宇宙学观测的影响可以忽略不计。然而，如果宇宙中能量分布存在各向异性应力，则矢量模具有增长模。在本文中，我们考虑了由自由流中微子维持的原始矢量模及其产生的磁场。首先，我们把一个观测约束的矢量模的数量从7年的WMAP数据。约束条件为，其中和分别是矢量和张量扰动振幅相对于标量扰动振幅的量。其次，我们计算了在给定约束条件下，原始矢量模不可避免地产生的磁场的谱，发现矢量模产生的最大磁场量由下式给出，其中是矢量模的谱指数。我们发现在辐射主导的时代，磁场产生的非平凡的取消，这在周围的磁场谱中创建了一个特征截止。
It is often stated that the cosmological vector mode has only a decaying mode and gives negligible effects on cosmological observations. The vector mode, however, has a growing mode if there exists anisotropic stress in energy distributions in the universe. In this paper, we consider a primordial vector mode sustained by free-streaming neutrinos and its associated magnetic field generation. First, we put an observational constraint on the amount of the vector mode from the 7-year WMAP data. The constraint is found as, whereandare the amounts of vector and tensor perturbation amplitudes with respect to the scalar one, respectively. Second, we calculate the spectrum of magnetic fields inevitably created from the primordial vector mode, given the constraint on. It is found that the maximum amount of magnetic fields generated from the vector mode is given by, withbeing a spectral index of the vector mode. We find a nontrivial cancellation of the magnetic field generation in the radiation-dominated era, which creates a characteristic cutoff in the magnetic field spectrum around.