Direct Calculation of Breather S Matrices

TL;DR

This paper develops a systematic Bethe-Ansatz method to compute breather S matrices in integrable quantum spin chains, specifically applying it to the open XXZ model with boundary fields and analyzing boundary scattering in the critical regime.

Contribution

It introduces a new systematic Bethe-Ansatz approach for calculating breather and soliton boundary S matrices in integrable models.

Findings

Calculated breather boundary S matrix for open XXZ chain with diagonal boundary fields.

Computed soliton boundary S matrix in the critical regime.

Established a framework for systematic S matrix calculations in integrable spin chains.

Abstract

We formulate a systematic Bethe-Ansatz approach for computing bound-state (``breather'') S matrices for integrable quantum spin chains. We use this approach to calculate the breather boundary S matrix for the open XXZ spin chain with diagonal boundary fields. We also compute the soliton boundary S matrix in the critical regime.