The Tensionless Limit of Pure-Ramond-Ramond AdS3/CFT2

Despite impressive advances in the AdS3/CFT2 correspondence, the setup involving Ramond-Ramond backgrounds, which is related to the D1-D5 system of branes, remained relatively poorly understood. We use the Mirror TBA equations recently constructed by Frolov and Sfondrini to study the spectrum of pure Ramond-Ramond $AdS_3\times S^3\times T^4$ strings. We find that the leading-order contribution to the anomalous dimensions at small tension is due to the gapless worldsheet excitations, i.e. to the $T^4$ bosons and their superpartners, whose interactions are nontrivial.