2000
We construct a large N matrix matrix model describing two-dimensional Euclidean string theory compactified on a circle of radius R and perturbed by an operator creating winding modes (vortices) on the worldsheet. The matrix model is exactly solvable and posesses an integrable structure of the infinite Toda chain hierarchy. We give explicit expressions for its free energy in the sphere-and torus approximation. A conjecture by V. Fateev, A. and Al. Zamolodchikov about the equivalence of the sine-Liouville and SL(2, R)/U(1) conformal field theories implies that for particular values of the parameters (vanishing cosmological constant µ and compactification radius R = 3 4 R KT ) the matrix model can be used to study two-dimensional string theory in the Euclidean black hole background to all orders in string perturbation theory.