Massless scattering in lower dimensional AdS/CFT

In recent years the framework of AdS/CFT integrability has seen a significant paradigm change due to the appearance of massless modes in the associated scattering problem. We shall briefly introduce the framework of the exact S-matrix theory and adapt it, following ideas of Zamolodchikov, to massless scattering, where we will make connections with integrable flows between conformal fixed points. We shall then translate this scenario to the case of AdS₃/CFT₂, and demonstrate the appearance of a 2D critical theory in the so-called Berenstein-Maldacena-Nastase limit of the integrable scattering problem.

This talk is primarily based on work with R. Borsato, A. Fontanella, O. Ohlsson Sax, A. Sfondrini, B. Stefanski and J. Stroemwall.