Non-perturbative calculation of the mass-gap in the Gross-Neveu model

We calculate a fully renormalizable effective action for local composite operators in the U(N) Gross-Neveu model, recently introduced by one of us, to two loop order. We obtain results for the massgap in one and two loops which are optimized using the Grunberg method of effective charges. At one loop the accuracy is of the order of 2% or less (except for N = 2). At two loops the accuracy is significantly improved for N ≥ 5.     

Soliton quantization in gauge theories

We present a simple quantization method for solitons in gauge theories based on a straight-forward application of pathintegral techniques. There is no zero mode problem and the intricacies of the canonical approach (the Dirac theory of constrained systems) are avoided.