Axion electrodynamics in the duality perspective

Axion electrodynamics is deduced from the local duality invariant electrodynamics (LDIE) with a new perspective on both formalism and the physical interpretation. First, the delicate issue of duality rotation symmetry in the Maxwell action is critically reviewed and the generalized Maxwell field equations invariant under local duality rotation are derived. In the alternative approach, a generalization is made to Sudbery's pseudo-vector action such that it is local duality invariant. Variational principle is used to derive the Euler-Lagrange equations of motion. The gauge potential for local duality rotation, termed duroton, under the assumption that it is a gradient of the axion field leads to the dual symmetric axion electrodynamics. The absence of the magnetic monopole in Maxwell equations motivates to impose a natural condition to deduce the standard axion electrodynamics. The present derivation offers the possibility for new physical interpretation of the axions and the monopoles.