Liouville strings in AdS3: the worldsheet story

A bstract The worldsheet σ -model of strings on AdS 3 with NS-NS fluxes can be equivalently described in terms of a Liouville field theory coupled to a timelike field with background charge, plus a marginal deformation. The operator that produces the deformation is non-normalizable and, from the string theory perspective, is associated to the spectral flow sector ω = −2. Its role is to control the winding number violation in scattering amplitudes. In the semiclassical (large k ) limit, the central charge of the Liouville factor tends to that of the dual CFT 2 , namely c ≃ 6 k . This may appear very similar to what occurs in the Liouville-type description of the dual deformed orbifold CFT 2 , where a twist-2 deformation operator dressed with a non-normalizable field also appears. Indeed, there are some similarities to that; however, there are also significant differences, which we discuss.