Alessandro Torrielli visited the University of Bologna last week and gave a Theory Group Seminar in the Department of Physics on Tuesday 10 December.  The talk was on “Yangians, massless modes and the AdS-3 string“.   In the talk he reviewed recent progress in understanding the exact scattering theory for the massive sector of strings propagating on AdS-3 backgrounds. The role of Yangians were highlighted, with particular emphasis on the new features displayed by this case when compared to the AdS-5 background, and the issues of massless modes in the theory were also discussed.