Wave propagation in axion electrodynamics

Understand

In this paper, the axion contribution to the electromagnetic wave propagation is studied.

• First we show how the axion electrodynamics model can be embedded into a premetric formalism of Maxwell electrodynamics.
• In this formalism, the axion field is not an arbitrary added Chern-Simon term of the Lagrangian, but emerges in a natural way as an irreducible part of a general constitutive tensor.We show that in order to represent the axion contribution to the wave propagation it is necessary to go beyond the geometric approximation, which is usually used in the premetric formalism.
• We derive a covariant dispersion relation for the axion modified electrodynamics.