Power spectrum of domain-wall network, and its implications for isotropic and anisotropic cosmic birefringence
Power spectrum of domain-wall network, and its implications for isotropic and anisotropic cosmic birefringence
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DOI：
10.1088/1475-7516/2022/10/043
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发表时间：
2022-05
影响因子：
6.4
通讯作者：
N. Kitajima;Fumiaki Kozai;F. Takahashi;W. Yin
中科院分区：
文献类型：
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作者：
N. Kitajima;Fumiaki Kozai;F. Takahashi;W. Yin
最近，基于对普朗克卫星数据的新分析，已经报道了宇宙微波背景光子的偏振的均匀旋转的暗示，称为各向同性宇宙双折射。建议的偏振旋转角约为0.2-0.4度，接近精细结构常数α = 1/137 rad = 0.42度。有趣的是，这种巧合可以在很宽的参数范围内自然地用轴子状粒子的畴壁来解释。此外，类轴子粒子畴壁不仅预测各向同性宇宙双折射，但也各向异性的，反映了类轴子粒子场的空间分布在最后的散射表面。在本文中，我们进行晶格模拟的畴壁在膨胀的宇宙中的形成和演化，并获得了第一次的两点相关函数和功率谱的标量场构成的畴壁。我们发现，在地平线下尺度的初始波动，功率谱是大致一致的分析预测的基础上随机壁分布。然而，在对应于哈勃半径的尺度上有一些多余。将我们的结果应用于各向异性宇宙双折射，我们预测了类似初始条件下由类轴粒子畴壁引起的旋转角的功率谱，并表明它是在未来宇宙微波背景观测的范围内。
Recently, based on a novel analysis of the Planck satellite data, a hint of a uniform rotation of the polarization of cosmic microwave background photons, called isotropic cosmic birefringence, has been reported. The suggested rotation angle of polarization of about 0.2–0.4 degrees is close to the fine-structure constant, α ≃ 1/137 rad ≃ 0.42 deg. Interestingly, this coincidence can be naturally explained over a very wide parameter range by the domain walls of axion-like particles. Furthermore, the axion-like particle domain walls predict not only isotropic cosmic birefringence but also anisotropic one that reflects the spatial distribution of the axion-like particle field on the last scattering surface. In this paper, we perform lattice simulations of the formation and evolution of domain walls in the expanding universe and obtain for the first time the two-point correlation function and power spectrum of the scalar field that constitutes the domain walls. We find that for initial fluctuations at subhorizon scales, the power spectrum is roughly consistent with analytical predictions based on random wall distributions. However, there is some excess at scales corresponding to the Hubble radius. Applying our results to the anisotropic cosmic birefringence, we predict the power spectrum of the rotation angles induced by the axion-like particle domain walls for the similar initial condition, and show that it is within reach of future observations of the cosmic microwave background.