Boundary scattering in the SU(N) principal chiral model on the half-line   with conjugating boundary conditions
  We investigate the SU(N) Principal Chiral Model on a half-line with a particular set of boundary conditions (BCs). In previous work these BCs have been shown to correspond to boundary scattering matrices (K-matrices) which are representation conjugating and whose matrix structure corresponds to one of the symmetric spaces SU(N)/SO(N) or SU(N)/Sp(N). Starting from the bulk particle spectrum and the K-matrix for a particle in the vector representation we construct K-matrices for particles in higher rank representations scattering off the boundary. We then perform an analysis of the physical strip pole structure and provide a complete set of boundary Coleman-Thun mechanisms for those poles which do not correspond to particles coupling to the boundary. We find that the model has no non-trivial boundary states. 
B. J. Short