A truly marginal deformation of SL(2,R) in a null direction
  We perform a marginal deformation of the SL(2,R) WZW model in a null direction. If we send the deformation parameter to infinity we obtain a linear dilaton background plus two free bosons. We show in addition that such a background can be obtained by a duality transformation of the undeformed WZW model. In the end we indicate how to generalize the given procedure. 
Stefan Forste