2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/57346A cluster expansion is proposed, that applies to both continuous and discrete systems. The assumption for its convergence involves an extension of the neat Kotecky-Preiss criterion. Expressions and estimates for correlation functions are also presented. The results are applied to systems of interacting classical and quantum particles, and to a lattice polymer model.11 pagesMathematical Physics82B05, 82B10text