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A Matrix Model for the 2d Black Hole

2000

Abstract

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.

Key takeaways

  • In this way we are able to reformulate the partition function of the string theory with the "cigar" background as the large N limit of a simple matrix integral, depending on the vortex couplings t m and the cosmological constant µ.
  • The string theory free energy (the partition function of connected surfaces) is a function of µ, λ and the string coupling g s .
  • In order to exploit this string/matrix correspondence, it is necessary to express explicitly the partition function (4.1) as a function of the moments λ n = tr Ω n , i.e.
  • • The scaling limit in the singlet sector of MQM: the canonical ensemble Consider first the ensemble with N fixed, which we call canonical (CE), saving the word grand canonical (GCE) for the ensemble with fixed µ.
  • In the limit y → 0, or µ → ∞ with λ fixed, we reproduce from (5.16) the known asymptotics of the c = 1 string theory unperturbed by vortices: