Calculation of the S-matrix of the massive Thirring model on a momentum space lattice

The S-matrix of the massive Thirring model is calculated non-perturbatively using a momentum space discretization. This represents the first application of this technique to a fermionic model. We find agreement up to 3 digits with 2nd order perturbation theory in the small coupling regime. Renormalization effects are found to be small. Our results do not support the old analytical solution of the S-matrix by Berezin and Sushko, but do support that of Zamolodchikov and Zamolodchikov. (orig.)