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arXiv 2305.01313gr-qc
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Weyl几何对引力场中光传播的影响

Weyl geometric effects on the propagation of light in gravitational fields

Marius A. Oancea, Tiberiu Harko

AI总结:

本研究推导Weyl几何中依赖偏振的光线方程,以静态球对称下推广Schwarzschild解的精确黑洞度规为例,数值研究光的引力自旋霍尔效应并估算Weyl矢量的影响。

摘要:

我们研究了Weyl几何对电磁波传播以及光的引力自旋霍尔效应的影响。通常认为,真空中电磁波沿零测地线传播,这一结论源于几何光学近似。但该模型仅在无限高频极限下成立,在大而有限的频率下,光线动力学受波的偏振影响,因此电磁波传播会偏离零测地线,这一现象被称为光的引力自旋霍尔效应。另一方面,麦克斯韦方程组具有显著的共形不变性,这一性质是Weyl几何及相应引力理论的基石。作为本研究的第一步,我们推导了Weyl几何中依赖偏振的光线方程,用以描述存在非度规性时光的引力自旋霍尔效应。作为Weyl几何中光自旋霍尔效应的具体例子,我们考虑了仅由Weyl标量平方和Weyl矢量强度构建的最简单共形不变作用量的情况。通过引入辅助标量场,该作用量在Weyl标量下被线性化。在静态球对称情形下,该理论存在一个精确黑洞解,它通过度规中两个新增项推广了标准的Schwarzschild解,这两个新增项分别与径向坐标呈线性和二次依赖关系。我们对该精确Weyl几何度规中依赖偏振的光线传播进行了数值研究,并估算了Weyl矢量的存在对自旋霍尔效应大小的影响。

英文摘要:

We consider the effects of Weyl geometry on the propagation of electromagnetic waves and on the gravitational spin Hall effect of light. It is usually assumed that in vacuum the electromagnetic waves propagate along null geodesics, a result which follows from the geometrical optics approximation. However, this model is valid only in the limit of infinitely high frequencies. At large but finite frequencies, the ray dynamics is affected by the wave polarization. Therefore, the propagation of the electromagnetic waves can deviate from null geodesics, and this phenomenon is known as the gravitational spin Hall effect of light. On the other hand, Maxwell's equations have the remarkable property of conformal invariance. This property is a cornerstone of Weyl geometry and the corresponding gravitational theories. As a first step in our study, we obtain the polarization-dependent ray equations in Weyl geometry, describing the gravitational spin Hall effect of light in the presence of nonmetricity. As a specific example of the spin Hall effect of light in Weyl geometry, we consider the case of the simplest conformally invariant action, constructed from the square of the Weyl scalar, and the strength of the Weyl vector only. The action is linearized in the Weyl scalar by introducing an auxiliary scalar field. In static spherical symmetry, this theory admits an exact black hole solution, which generalizes the standard Schwarzschild solution through the presence of two new terms in the metric, having a linear and a quadratic dependence on the radial coordinate. We numerically study the polarization-dependent propagation of light rays in this exact Weyl geometric metric, and the effects of the presence of the Weyl vector on the magnitude of the spin Hall effect are estimated.

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