2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/25307The main purpose of this chapter is to present a brief introduction to nonlinear excitations, and to underline the soliton concept. This chapter is Chapter 5 in the book High-Temperature Superconductivity: The Nonlinear Mechanism and Tunneling Measurements (Kluwer Academic, Dordrecht, 2002), pages 101-142.21 pages in RevTEX format, including 25 figuresSuperconductivityStrongly Correlated Electronstext