SL(2,R)CIRCLE-TIMES-SU(2)/R(2) STRING MODEL IN CURVED SPACETIME AND EXACT CONFORMAL RESULTS

Pursuing further the recent methods in the algebraic hamiltonian approach to gauged WZW models, we apply them to the bosonic SL(2,R)-k' x SU(2)k/(R x R) model recently investigated by Nappi and Witten. We find the global space and compute the conformally exact metric and dilaton fields to all orders in the 1 / k expansion. The semiclassical limit k', k --> infinity of our exact results agree with the lowest order perturbation computation which was done in the lagrangian formalism. We also discuss the supersymmetric type-II and heterotic versions of this model and verify the non-renormalization of epsilon(PHI) square-root -G.