2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/94460Self-localized modes in a quantum vibronic system, with long range interaction of Kac-Baker type and interacting nonlinearly with an acoustical phonon bath, is studied. One works in the coherent state approximation. Following a procedure of Sarker and Krumhansl, the problem is reduced to a nearest neighbours one. In the continuum limit the localized state satisfy a mKdV equation. An approximate expression for its frequency is found.Proceedings of the Conference "Path-Integral from pev to TeV. 50 years from Feynman's paper", Florence, August 1998, 4 pages, latex, sprocl.styExactly Solvable and Integrable SystemsCondensed Mattertext