TT deformed CFT as a non-critical string

A bstract We present a new exact treatment of TT T T ¯ deformed 2D CFT in terms of the worldsheet theory of a non-critical string. The transverse dimensions of the non-critical string are represented by the undeformed CFT, while the two longitudinal light-cone di- rections are described by two scalar fields X + and X − with free field OPE’s but with a modified stress tensor, arranged so that the total central charge adds up to 26. The relation between our X ± field variables and 2D dilaton gravity is indicated. We compute the physical spectrum and the partition function and find a match with known results. We describe how to compute general correlation functions and present an integral expression for the three point function, which can be viewed as an exact formula for the OPE coefficients of the TT T T ¯ deformed theory. We comment on the relationship with other proposed definitions of local operators.