Superstrings on NS5 backgrounds, deformed AdS3 and holography

Abstract

We study a non-standard decoupling limit of the D1/D5-brane system, which interpolates between the near-horizon geometry of the D1/D5 background and the near-horizon limit of the pure D5-brane geometry. The S-dual description of this background is actually an exactly solvable two-dimensional (worldsheet) conformal field theory: {null-deformed SL(2, ℝ)} × SU(2) × T4 or K3. This model is free of strong-coupling singularities. By a careful treatment of the SL(2, ℝ), based on the better-understood SL(2, ℝ)/U(1) coset, we obtain the full partition function for superstrings on SL(2, ℝ) × SU(2) × T4/ℤ2. This allows us to compute the partition functions for the J3 J̄3 and J2J̄2 deformations, as well as the full line of supersymmetric null deformations, which links the SL(2,ℝ) conformal field theory with linear-dilaton theory. The holographic interpretation of this setup is a renormalization-group flow between the decoupled NS5-brane world-volume theory in the ultraviolet (little string theory), and the low-energy dynamics of super Yang-Mills string-like instantons in six dimensions. © SISSA/ISAS 2003.