2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/226733In this talk a sufficient condition for a diagonal orthogonally transitive cylindrical $G_2$ metric to be geodesically complete is given. The condition is weak enough to comprise all known diagonal perfect fluid cosmological models that are non-singular.4 pp. Proceedings of ERE'98General Relativity and Quantum Cosmologytext