We consider a space-time-invariant duality symmetric action for a free Maxwell field and an SL(2,R)×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.

• Received 20 June 1995

DOI:https://doi.org/10.1103/PhysRevD.52.R4277