Boundary S-matrix for the Gross-Neveu model

We study the scattering theory for the Gross-Neveu model on the half-line. We find the reflection matrices for the elementary fermions, and by fusion we compute the ones for the two-particle bound-states, showing that they sa ti,fy non-trivial bootstrap consistency conditions. We also compute more ge neral reflection matrices for the Gross-Neveu model and the nonlinear sigma model, and argue that they correspond to the integrable boundary condition s we identified in our previous paper [5]. (C) 1999 Published by Elsevier S cience B.V. All rights reserved.