Primordial magnetic fields generated by the non-adiabatic fluctuations at pre-recombination era
Primordial magnetic fields generated by the non-adiabatic fluctuations at pre-recombination era
复制标题
预复合时代非绝热涨落产生的原始磁场
DOI：
10.1088/1475-7516/2011/11/045
复制
发表时间：
2011
影响因子：
6.4
通讯作者：
K.Ichiki
中科院分区：
文献类型：
--
作者：
S.Maeda;K.Takahashi;K.Ichiki
在预复合时代，宇宙密度涨落可以通过汤姆逊散射自然产生磁场。在以前的研究中，仅考虑了初始绝热涨落产生的磁场。在这里，我们基于宇宙学摄动理论，利用光子和重子流体之间的紧耦合近似，研究了由原初非绝热涨落产生的宇宙磁场的产生。研究发现，非绝热涨落产生的磁场可以在紧耦合近似的一阶展开时产生。该结果与绝热初始涨落的情况形成对比，在绝热初始涨落中只能产生二阶磁场。在一般情况下，原始密度扰动在主要绝热扰动的顶部包含小的非绝热涨落，我们表明磁场的主要来源是由绝热和非绝热涨落的二阶耦合给出的。我们计算了当非绝热涨落具有蓝色功率谱时产生的磁场的功率谱，这是最近的宇宙学观测所表明的。
In the pre-recombination era, cosmological density fluctuations can naturally generate magnetic fields through Thomson scatterings. In previous studies, only the magnetic field generation from the initially-adiabatic fluctuations has been considered. Here we investigate the generation of cosmological magnetic fields sourced by the primordial non-adiabatic fluctuations based on the cosmological perturbation theory, using the tight-coupling approximations between photon and baryon fluids. It is found that the magnetic fields from the non-adiabatic fluctuations can arise at the first-order expansion of the tight coupling approximation. This result is in contrast to the case of adiabatic initial fluctuations, where the magnetic fields can be generated only at the second-order. In a general case where the primordial density perturbations contain small non-adiabatic fluctuations on the top of the dominant adiabatic ones, we show that the leading source of magnetic fields is given by the second-order coupling of the adiabatic and non-adiabatic fluctuations. We calculate the power spectrum of the generated magnetic fields when the non-adiabatic fluctuations have a blue power spectrum, which has been suggested by recent cosmological observations.