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

Roberto Casadio, Benjamin Harms
1996 Physics Letters B  
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.
doi:10.1016/s0370-2693(96)01253-1 fatcat:recijd2qi5aphiwazoshpsfbru