We propose a world-sheet realization of the zigzag-invariant strings as a perturbed WZNW model at large negative level. We argue that the gravitational dressing produces additional fixed points of the dressed renormalization beta function. One of these new critical points can be interpreted as a zigzag-invariant string model. ∗e-mail: [email protected] †e-mail: [email protected]...

Abstract We discuss solutions of the heterotic string theory which are analogous to bosonic and superstring backgrounds related to coset conformal field theories. A class of exact ‘left-right symmetric’ solutions is obtained by supplementing the metric, antisymmetric tensor and dilaton of the superstring solutions by the gauge field background equal to the generalised Lorentz connection with to...

We study the semi-infinite or BRST cohomology of affine Lie algebras in detail. This cohomology is relevant in the BRST approach to gauged WZNW models. Our main result is to prove necessary and sufficient conditions on ghost numbers and weights for non-trivial elements in the cohomology. In particular we prove the existence of an infinite sequence of elements in the cohomology for non-zero ghos...