Duality groups as (spontaneously broken) gauge symmetries for toroidal backgrounds, and their role in (∞-dimensional) underlying string gauge algebras are reviewed. For curved backgrounds, it is shown that there is a duality in the moduli space of WZNW sigma-models, that can be interpreted as a broken gauge symmetry. In particular, this duality relates the backgrounds corresponding to axially g...

It is shown that there exists a truly marginal deformation of the direct sum of two Gk WZNW models at k = −2cV (G) (where cV (G) is the eigenvalue of the quadratic Casimir operator in the adjoint representation of the group G) which does not seem to fit the Chaudhuri-Schwartz criterion for truly marginal perturbations. In addition, a continuous family of WZNW models is constructed.

We consider two level k WZNW models coupled to each other through a generalized Thirring-like current-current interaction. It is shown that in the large k limit, this interacting system can be presented as a two-parameter perturbation around a nonunitary WZNW model. The perturbation operators are the sigma model kinetic terms with metric related to the Thirring coupling constants. The renormali...

The gauged SL(2,R)/U(1) Wess-Zumino-Novikov-Witten (WZNW) model is classically an integrable conformal field theory. We have found a Lax pair representation for the non-linear equations of motion, and a Bäcklund transformation. A second-order differential equation of the Gelfand-Dikii type defines the Poisson bracket structure of the theory, and its fundamental solutions describe the general so...

We use the conformal Ward identities to study the structure of correlation functions in coset conformal field theories. For a large class of primary fields of arbitrary g/h theory a factorization anzatz is found.Corresponding correlation functions are explicitly expressed in terms of correlation functions of two independent WZNW theories for g and h. Coset theories is an important subclass of t...

We discuss special perturbations of the gauged level k WZNW model inspired by the σ-model perturbation of the nonunitary WZNW model. In the large k limit there is a second conformal point in the vicinity of the ultarviolet fixed point. At the second critical point the conformal model has a rational Virasoro central charge which no longer corresponds to a coset construction. In spite of this fac...

It is shown that the master equation of the affine-Virasoro construction on the unitary affine algebra naturally emerges in the fusion algebra of the nonunitary level k WZNW model. Operators corresponding to solutions of the master equation are suitable for performing one-parametrical renormalizable perturbation around the given conformal nonunitary WZNW model. In the large |k| limit, the infra...

Motivated by a careful analysis of the Laplacian on the supergroup SU(2|1) we formulate a proposal for the state space of the SU(2|1) WZNW model. We then use properties of ŝl(2|1) characters to compute the partition function of the theory. In the special case of level k = 1 the latter is found to agree with the properly regularized partition function for the continuum limit of the integrable sl...