We use relativistic invariance to investigate two aspects of integrable AdS3 string theory. Firstly, we write down the all-loop TBA equations for the massless sector of the theory with R-R flux, using the recently discovered hidden relativistic symmetry. Secondly, for the low-energy relativistic limit of the theory with NS-NS flux we write down the S matrix, dressing factors and TBA. We find that the integrable system coincides with a restriction to AdS3 of the relativistic q-deformed AdS5 theory.We also comment on the relativistic limit of the small-k NS-NS theory. 1 andrea.fontanella@inv.uam.es 2 olof.ohlsson.sax@nordita.org 3 Bogdan.Stefanski.1@city.ac.uk 4 a.torrielli@surrey.ac.uk
AcknowledgmentsWe very much thank Diego Bombardelli for discussions, collaboration on the initial stages of the project and continuing assistance. We very much thank Ben Hoare, Tim Hollowood and Arkady Tseytlin for reading the manuscript and for very useful comments and discussions. We thank Alessandra Cagnazzo,