2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/57391An emended and improved version of the present paper has been archived in math-ph/0505057, and a preliminary account of its content has been published in Phys.Rev.Lett. 92, 60601, (2004). Moreover, in order to prove the relevance of topology for phase transition phenomena in a broad domain of physically interesting cases, we have proved another theorem which is reported in math-ph/0505058 and which is crucially based on the result of the paper archived in math-ph/0505057.This paper has been superseded by math-ph/0505057 and math-ph/0505058Mathematical PhysicsStatistical MechanicsHigh Energy Physics - TheoryDifferential GeometryGeometric Topology82B26; 82B03; 82B05; 58E05text