Perturbing the symmetric orbifold from the worldsheet

The symmetric orbifold of ${\mathbb{T}}^4$ is the analogue of free SYM in four dimensions, and its dual is described by a tensionless string propagating in ${\mathrm{A}\mathrm{d}\mathrm{S}}_3\times {\mathrm{S}}^3\times {\mathbb{T}}^4$. In this paper we study the deformation of this exact AdS/CFT duality away from the free point. On the symmetric orbifold side this amounts to perturbing the theory by the exactly marginal operator from the $2$-cycle twisted sector. We identify the corresponding perturbation in the dual worldsheet description, and show that the anomalous conformal dimensions of a number of symmetric orbifold currents are correctly reproduced from this worldsheet perspective.