2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48526A brief summary of the mathematical structure of the Lee-Friedrichs model is given, including the natural extension of its Hamiltonian to a Gel'fand triple, containing a generalized eigenstate for the complex pole. Contains references to some physical applications and relativistic generalizations.To be published in Kluwer Encyclopedia of Mathematics;reviewHigh Energy Physics - Phenomenologytext