Fermion Bag Solitons in the Massive Gross-Neveu and Massive   Nambu-Jona-Lasinio Models in 1+1 Dimensions: Inverse Scattering Analysis
  Formation of fermion bag solitons is an important paradigm in the theory of hadron structure. We report here on our non-perturbative analysis of this phenomenon in the 1+1 dimensional massive Gross-Neveu model, in the large $N$ limit. Our main result is that the extremal static bag configurations are reflectionless, as in the massless Gross-Neveu model. Explicit formulas for the profiles and masses of these solitons are presented. We also present a particular type of self-consistent reflectionless solitons which arise in the massive Nambu-Jona-Lasinio models, in the large-N limit. 
Joshua Feinberg and Shlomi Hillel