2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/18602Interesting physical results can be obtained from sigma models by taking the number of fields N to zero. I discuss how one can make sense of this limit by using exact S matrix techniques. I review how this can be done for the case of self-avoiding polymers, and speculate on the application to the replica limit of disordered systems.12 pages, 1 figure. Contribution to the proceedings of the NATO Advanced Research Workshop on Statistical Field Theories, Como 18-23 June 2001Statistical MechanicsStrongly Correlated Electronstext