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arXiv 2105.00829hep-thgr-qc
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宇宙弦和紧化在AdS体上诱导的费米子凝聚中的拓扑效应

Topological effects in fermion condensate induced by cosmic string and compactification on AdS bulk

S. Bellucci, W. Oliveira dos Santos, E. R. Bezerra de Mello, A. A. Saharian

摘要:

研究了在具有紧致维数的5维局域反德西特(AdS)时空背景下,在有磁通量的宇宙弦存在下,大质量旋量场的费米子凝聚. FC被分解为两个贡献。第一个对应于没有紧化的几何,第二个是由紧化诱导的。根据参数的值,总FC可以是正的或负的。作为一种极限情况,导出了局部闵可夫斯基时空上FC的表达式。在无质量的费米子场中,它为零,而在无质量的情况下,AdS体上的非零FC是引力引起的效应。这表明引力场对相变的参数空间有着本质的影响。对于一个大质量场,FC在弦上的发散是与弦的适当距离的倒数立方。在无质量场的情况下,取决于沿着弦的磁通量和平面角亏损,弦上的FC的极限值可以是有限的或无限的。在大的距离上,FC的衰减作为到弦的距离的函数,对于有质量场和无质量场都是幂律的。对于闵可夫斯基体上的宇宙弦和大质量场,衰变是指数的。FC中的拓扑部分在AdS边界上消失。我们证明了实现Clifford代数的两个不等价的不可约表示的域的FC是一致的。在零平面角亏损的特殊情况下,本文给出的结果描述了弯曲时空中由磁通量引起的Aharonov-Bohm型效应。

英文摘要:

We investigate the fermion condensate (FC) for a massive spinor field on background of the 5-dimensional locally anti-de Sitter (AdS) spacetime with a compact dimension and in the presence of a cosmic string carrying a magnetic flux. The FC is decomposed into two contributions. The first one corresponds to the geometry without compactification and the second one is induced by the compactification. Depending on the values of the parameters, the total FC can be either positive or negative. As a limiting case, the expression for the FC on locally Minkowski spacetime is derived. It vanishes for a massless fermion field and the nonzero FC on the AdS bulk in the massless case is an effect induced by gravitation. This shows that the gravitational field may essentially influence the parameters space for phase transitions. For a massive field the FC diverges on the string as the inverse cube of the proper distance from the string. In the case of a massless field, depending on the magnetic flux along the string and planar angle deficit, the limiting value of the FC on the string can be either finite or infinite. At large distances, the decay of the FC as a function of the distance from the string is power law for both cases of massive and massless fields. For a cosmic string on the Minkowski bulk and for a massive field the decay is exponential. The topological part in the FC vanishes on the AdS boundary. We show that the FCs coincide for the fields realizing two inequivalent irreducible representations of the Clifford algebra. In the special case of the zero planar angle deficit, the results presented in this paper describe Aharonov-Bohm-type effects induced by magnetic fluxes in curved spacetime.

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