Poincaré coset models [Formula presented] and [Formula presented] duality

We generalize a family of Lagrangians with values in the Poincaré group (Formula presented) which contain the description of spinning strings in flat (Formula presented) dimensions, by including symmetric terms in the world-sheet coordinates. Then, by promoting a subgroup (Formula presented) (Formula presented) which acts invariantly from the left on the element of (Formula presented) to a gauge symmetry of the action, we obtain a family of (Formula presented) models. They describe bosonic strings moving in (generally) curved, and in some cases degenerate, space-times with an axion field. Further, the space-times of the effective theory admit in general (Formula presented)-dual geometries. We give explicit results for two nondegenerate cases. © 1998 The American Physical Society.