Singularities of the Magnon Boundstate S-Matrix

TL;DR

This paper analyzes the singularities of the exact S-matrix for BPS magnon boundstates in N=4 SUSY Yang-Mills, showing that all poles correspond to physical on-shell intermediate states.

Contribution

It provides a detailed account of the poles in the conjectured S-matrix, confirming their physical origin in the known BPS spectrum.

Findings

All poles are explained by on-shell intermediate particles.

Poles near the real axis correspond to physical scattering processes.

The analysis supports the consistency of the conjectured S-matrix.

Abstract

We study the conjectured exact S-matrix for the scattering of BPS magnon boundstates in the spin-chain description of planar N=4 SUSY Yang-Mills. The conjectured S-matrix exhibits both simple and double poles at complex momenta. Some of these poles lie parametrically close to the real axis in momentum space on the branch where particle energies are positive. We show that all such poles are precisely accounted for by physical processes involving one or more on-shell intermediate particles belonging to the known BPS spectrum.