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, IR) −k ′ ⊗SU (2) k /(IR⊗˜IR) 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 → ∞ 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 e Φ √ −G.