2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/227397We study a model that the entropy per particle in the universe is constant. The sources for the entropy are the particle creation and a lambda decaying term. We find exact solutions for the Einstein field equations and show the compatibilty of the model with respect to the age and the acceleration of the universe.10 pages, 2 figuresGeneral Relativity and Quantum Cosmologytext