Macroscopic quantum electrodynamics and duality

TL;DR

This paper investigates the conditions under which electric-magnetic duality symmetry holds in macroscopic quantum electrodynamics, showing invariance of key physical quantities and enabling the derivation of new physical insights from known configurations.

Contribution

It establishes the conditions for duality invariance in macroscopic quantum electrodynamics and demonstrates the invariance of important physical quantities under electric-magnetic exchange.

Findings

Maxwell's equations without free charges are duality invariant at the operator level.

Casimir forces and van-der-Waals potentials are invariant under electric-magnetic exchange.

Duality symmetry can be used to infer new physical configurations from existing ones.

Abstract

We discuss under what conditions the duality between electric and magnetic fields is a valid symmetry of macroscopic quantum electrodynamics. It is shown that Maxwell's equations in the absence of free charges satisfy duality invariance on an operator level, whereas this is not true for Lorentz forces and atom--field couplings in general. We prove that derived quantities like Casimir forces, local-field corrected decay rates as well as van-der-Waals potentials are invariant with respect to a global exchange of electric and magnetic quantities. This exact symmetry can be used to deduce the physics of new configurations on the basis of already established ones.