2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/192169We obtain new duality transformations relating some exact string backgrounds, by defining the nilpotent duality. We show that the ungauged $SL(2, R)$ WZW model transforms by its action into the three dimensional plane wave geometry. We also give the inverse transformation from the plane wave to the $SL(2, R)$ model and discuss the implications of the results.12 pagesHigh Energy Physics - Theorytext