On-shell Diagrams Research Articles

Exact S-matrices for bound states of a2(1) affine Toda solitons

Using Hollowood's conjecture for the S-matrix for elementary solitons in complex a n (1) affine Toda field theories we examine the interactions of bound states of solitons in a 2 (1) theory. The elementary solitons can form two different kinds of bound states: scalar bound states (the so-called breathers), and excited solitons, which are bound states with non-zero topological charge. We give explicit expressions of all S-matrix elements involving the scattering of breathers and excited solitons and examine their pole structure in detail. It is shown how the poles can be explained in terms of on-shell diagrams, several of which involve a generalized Coleman-Thun mechanism.