arXiv 1706.007492017-06-02hep-thgr-qcquant-ph

de Sitter时空中宇宙弦周围的电磁真空涨落

Electromagnetic vacuum fluctuations around a cosmic string in de Sitter spacetime

A. A. Saharian, V. F. Manukyan, N. A. Saharyan

备注：: 19 pages, 2 figures
发表信息：: Eur. Phys. J. C (2017) 77:478
DOI：: 10.1140/epjc/s10052-017-5047-7

摘要：

假设场是在Bunch-Davies真空态下制备的，计算了$(D+1)$维dS时空背景中宇宙弦周围的电磁场散射子.的分解形式，其中弦诱导的拓扑部分被明确提取？通过这种分解，在符合极限下的局部真空期望值（VEVs）的重整化被简化为在没有宇宙弦的情况下的dS时空的重整化。研究了电场和磁场的平方以及真空能量密度的VEV。在弦附近，拓扑贡献占主导地位，背景引力场的影响很小。在这个区域中，拓扑贡献中的主导项是从闵可夫斯基体上的弦的相应VEV乘以共形因子得到的。在距离弦大于背景几何的曲率半径时，VEV中的纯dS部分占主导地位。在该区域，对于空间维度$D>3$，引力场对拓扑贡献的影响至关重要，相应的行为与闵可夫斯基体上的宇宙弦有本质上的不同。有动机良好的暴胀模型产生宇宙弦。我们认为，作为超哈勃电磁涨落在暴胀过程中量子到经典跃迁的结果，在后暴胀时代，这些弦将被大尺度随机磁场所包围。这些场可能是在暴胀过程中产生的宇宙弦以及相应的暴胀模型的显著特征之一。

英文摘要：

The electromagnetic field correlators are evaluated around a cosmic string in background of $(D+1)$-dimensional dS spacetime assuming that the field is prepared in the Bunch-Davies vacuum state. The correlators are presented in the decomposed form where the string-induced topological parts are explicitly extracted. With this decomposition, the renormalization of the local vacuum expectation values (VEVs) in the coincidence limit is reduced to the one for dS spacetime in the absence of the cosmic string. The VEVs of the squared electric and magnetic fields, and of the vacuum energy density are investigated. Near the string they are dominated by the topological contributions and the effects induced by the background gravitational field are small. In this region, the leading terms in the topological contributions are obtained from the corresponding VEVs for a string on the Minkowski bulk multiplying by the conformal factor. At distances from the string larger than the curvature radius of the background geometry, the pure dS parts in the VEVs dominate. In this region, for spatial dimensions $D>3$, the influence of the gravitational field on the topological contributions is crucial and the corresponding behavior is essentially different from that for a cosmic string on the Minkowski bulk. There are well-motivated inflationary models which produce cosmic strings. We argue that, as a consequence of the quantum-to-classical transition of super-Hubble electromagnetic fluctuations during inflation, in the postinflationary era these strings will be surrounded by large scale stochastic magnetic fields. These fields could be among the distinctive features of the cosmic strings produced during the inflation and also of the corresponding inflationary models.

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