2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/152297We propose a new construction of Banach-Lie groups and algebras relying on nonstandard analysis. A major standard application is the Local Theorem which to certain extent reduces the problem of associating a Lie group to a given banach-Lie algebra to a similar problem for finitely generated Lie subalgebras. We discuss possible applications, e.g., to gauge theories.12 pagesFunctional AnalysisOperator Algebrastext