Soliton formation in the Nambu-Jona-Lasinio model

The soliton formation is considered in the Nambu-Jona-Lasinio model with lo cal four quark interaction and various schemes to regularize the energy con tribution of the polarized vacuum. No additional constraints are admitted i n order to stabilize the soliton. While solitons are unstable in the proper -time regularized version the three-momentum cut-off regularization apparen tly is more appropriate. Using a semi-classical approach multi-quark solito ns obtained from that scheme are discussed. However, no self-consistent non -trivial unit baryon number configuration has been found. We also study a r enormalizable extension of the model. In this case no stable multi-quark so litons are obtained within the semi-classical approach. (C) 2000 Published by Elsevier Science B.V. All rights reserved.