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arXiv 1407.8095hep-thgr-qc
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紧化宇宙弦存在时de Sitter时空中的感生费米子流

Induced fermionic currents in de Sitter spacetime in the presence of a compactified cosmic string

A. Mohammadi, E. R. Bezerra de Mello, A. A. Saharian

摘要:

本文研究了deSitter时空背景下紧致宇宙弦几何中的真空费米子流。这些电流是由沿着宇宙弦运行的磁通量感应的,并被致密维度所包围。我们发现,真空电荷和电流密度的径向分量消失。利用Abel-Plana求和公式,将方位流和轴向流分解为两部分:第一部分对应于直宇宙弦的几何结构,第二部分由弦沿其轴向的紧化引起.对于轴向电流,第一部分为零,相应的拓扑部分是沿弦轴的磁通量的偶周期函数和由紧维包围的磁通量的奇周期函数,其周期等于磁通量量子。方位电流密度是弦轴上磁通量的奇周期函数,是同一周期的紧维所围磁通量的偶周期函数。取决于磁通量,平面角亏损可以增强或减小方位电流和轴向电流。背景引力场对真空流的影响在离弦的距离大于德西特曲率半径时是至关重要的。特别是,对于一个直的宇宙弦的几何形状和一个大规模的费米子场,我们表明,方位电流密度的衰减是阻尼振荡的振幅与距离的四次方成反比的字符串。这种行为与闵可夫斯基体中的弦的情况形成鲜明对比,在闵可夫斯基体中,电流密度在大距离处被指数抑制。

英文摘要:

We investigate the vacuum fermionic currents in the geometry of a compactified cosmic string on background of de Sitter spacetime. The currents are induced by magnetic fluxes running along the cosmic string and enclosed by the compact dimension. We show that the vacuum charge and the radial component of the current density vanish. By using the Abel-Plana summation formula, the azimuthal and axial currents are explicitly decomposed into two parts: the first one corresponds to the geometry of a straight cosmic string and the second one is induced by the compactification of the string along its axis. For the axial current the first part vanishes and the corresponding topological part is an even periodic function of the magnetic flux along the string axis and an odd periodic function of the flux enclosed by the compact dimension with the periods equal to the flux quantum. The azimuthal current density is an odd periodic function of the flux along the string axis and an even periodic function of the flux enclosed by the compact dimension with the same period. Depending on the magnetic fluxes, the planar angle deficit can either enhance or reduce the azimuthal and axial currents. The influence of the background gravitational field on the vacuum currents is crucial at distances from the string larger than the de Sitter curvature radius. In particular, for the geometry of a straight cosmic string and for a massive fermionic field, we show that the decay of the azimuthal current density is damping oscillatory with the amplitude inversely proportional to the fourth power of the distance from the string. This behavior is in clear contrast with the case of the string in Minkowski bulk where the current density is exponentially suppressed at large distances.

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