Duality symmetric actions with manifest space-time symmetries

Abstract
We consider a space--time invariant duality symmetric action for the free Maxwell field and an SL(2,{\bf R})\times SO(6,22) invariant effective action describing a low--energy bosonic sector of the heterotic string compactified on a six--dimensional torus. The manifest Lorentz and general coordinate invariant formulation of the models is achieved by coupling dual gauge fields to an auxiliary vector field from an axionic sector of the theory