Nonlocal Symmetries and Factorized Scattering

Conventionally, factorized scattering in two dimensions is argued to be a consequence of the conservation of local higher charges. However, integrability may well be realized via nonlocal charges, while higher local charges are not known. Here we address the question of whether a nonlocal Yangian symmetry implies factorized scattering of the S-matrix. We explicitly study the constraints on three-particle scattering processes of particles transforming in the fundamental representations of su(N), u(1|1), and the centrally extended su(2|2) underlying the dynamic scattering and hexagon form factors in AdS/CFT. These considerations shed light on the role of the Yangian as an axiomatic input for the bootstrap program for integrable theories.