Space-time singularities and the axion in the Poincare coset models ISO(2,1)/H

Abstract

By promoting an invariant subgroup $H$ of $ISO(2,1)$ to a gauge symmetry of a WZWN action, we obtain the description of a bosonic string moving either in a curved 4-dimensional space--time with an axion field and curvature singularities or in 3-dimensional Minkowski space--time.Comment: LaTeX, 6 pages plus 2 figures in a separate postscript file, a LaTeX error fixe