Karch A
Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA.
Phys Rev Lett. 2009 Oct 23;103(17):171601. doi: 10.1103/PhysRevLett.103.171601. Epub 2009 Oct 19.
We work out the action of the SL(2,Z) electric-magnetic duality group for an insulator with a nontrivial permittivity, permeability, and theta angle. This theory has recently been proposed to be the correct low-energy effective action for topological insulators. As applications, we give manifestly SL(2,Z) covariant expressions for the Faraday rotation at orthogonal incidence at the interface of two such materials, as well as for the induced magnetic and electric charges, slightly clarifying the meaning of expressions previously derived in the literature. We also use electric-magnetic duality to find a gravitational dual for a strongly coupled version of this theory using the gauge/gravity correspondence.
我们推导出了具有非平凡电容率、磁导率和θ角的绝缘体的SL(2,Z)电磁对偶群的作用。该理论最近被提议作为拓扑绝缘体正确的低能有效作用。作为应用，我们给出了两种此类材料界面处正交入射时法拉第旋转以及感应磁荷和电荷的明显SL(2,Z)协变表达式，略微澄清了文献中先前推导表达式的含义。我们还利用电磁对偶，通过规范/引力对应关系找到了该理论强耦合版本的引力对偶。
