Tensionless limit of pure-Ramond-Ramond AdS3/CFT2 superstring

The $AdS_3\times S^3\times T^4$ spacetime with pure Ramond-Ramond flux, related to the D1-D5 system, is believed to be integrable as in $AdS_5\times S^35$. The integrability approaches to AdS3/CFT2 and the mirror TBA equations to study the energy spectrum are reviewed. By solving the TBA for massless excited states at small coupling, we find that the leading-order contribution to the anomalous dimensions includes massless wrapping corrections, and behave as a sort of free particles. This talk is based on the works with Alberto Brollo, Dennis le Plat and Alessandro Sfondrini.