NOTE ON MANIFEST LORENTZ AND GENERAL COORDINATE INVARIANCE IN DUALITY SYMMETRIC MODELS.

We consider a generalization of a duality symmetric model proposed by Schwarz and Sen. It is based on enlarging the model with a dynamical vector field being a time-like component of a local Lorentz frame. This allows one to preserve the manifest Lorentz invariance of the model in flat space--time. The presence of this field is regarded as a relic of gravitational interaction which respects the general coordinate invariance in curved space--time but breaks the local Lorentz symmetry in tangent space down to its spatial subgroup.