A study of integrable form factors in massless relativistic AdS2

Abstract

In this paper we initiate the study of form factors for the massless scattering of integrable AdS2 superstrings, where the difference-form of the S-matrix can be exploited to implement the relativistic form factor bootstrap. The non-standard nature of the S-matrix implies that traditional methods do not apply. We use the fact that the massless AdS2S-matrix is a limit of a better-behaved S-matrix found by Fendley. We show that the previously conjectured massless AdS2 dressing factor coincides with the limit of the De Martino-Moriconi improved dressing factor for the Fendley S-matrix. We then solve the form factor constraints in the two-particle case. Along the way we find a method to construct integral representations of relativistic dressing factors satisfying specific assumptions, and use it to obtain analytic proofs of crossing and unitarity relations.