标题： 电磁耦合在电动力学中 显示英文标题

标题： The magnetoelectric coupling in Electrodynamics

摘要： 我们探索了一个类似于轴子电动力学的模型，其中轴子场$\theta (t,\mathbf{x})$而不是作为动力学变量，而是作为一个分段常数的有效参数$\theta$，编码了介质的微观特性，如其介电常数或磁导率，定义了我们所谓的$\theta$-介质。 该模型描述了一大类现象，其中我们强调具有拓扑序的材料的电磁响应，例如拓扑绝缘体。 我们追求对$\theta$-介质典型的边界值问题的格林函数公式，当给出外部源或边界条件时。 作为我们方法的例证，我们也将其扩展到了有质量的介质，我们将常数$\theta$解释为真空的一种新拓扑性质，即所谓的$\theta$-真空，并将我们的讨论限制在介质的介电常数和磁导率均为一的情况。 这样，我们集中于额外的$\theta$耦合所产生的显著的磁电效应。 电磁辐射的边界条件问题是卡西米尔效应出现的关键，因此我们应用上述方法作为另一种方式来研究引入拓扑绝缘体对卡西米尔效应的修改。 显示英文摘要

摘要： We explore a model akin to axion electrodynamics in which the axion field $\theta (t,\mathbf{x})$ rather than being dynamical is a piecewise constant effective parameter $\theta$ encoding the microscopic properties of the medium inasmuch as its permittivity or permeability, defining what we call a $\theta$-medium. This model describes a large class of phenomena, among which we highlight the electromagnetic response of materials with topological order, like topological insulators for example. We pursue a Green's function formulation of what amounts to typical boundary-value problems of $\theta$-media, when external sources or boundary conditions are given. As an illustration of our methods, which we have also extended to ponderable media, we interpret the constant $\theta$ as a novel topological property of vacuum, a so called $\theta$-vacuum, and restrict our discussion to the cases where the permittivity and the permeability of the media is one. In this way we concentrate upon the effects of the additional $\theta$ coupling which induce remarkable magnetoelectric effects. The issue of boundary conditions for electromagnetic radiation is crucial for the occurrence of the Casimir effect, therefore we apply the methods described above as an alternative way to approach the modifications to the Casimir effect by the inclusion of topological insulators.