2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/76175Gelfand-Naimark duality (Commutative $C^*$-algebras $\equiv$ Locally compact Hausdorff spaces) is extended to $C^*$-algebras $\equiv$ Quotient maps on locally compact Hausdorff spaces. Using this duality, we give for an \emph{arbitrary} bounded operator on a complex Hilbert space of several dimensions, a functional calculus and the existence theorem for nontrivial invariant subspace.Under consideration for publication by Electronic Reasearch Announcements of the AMSFunctional AnalysisOperator Algebras46L05; 47A13; 47A13; 43A40; 22B05Noncommmutative Gelfand Duality for not necessarily unital $C^*$-algebras, Jordan Canonical form, and the existence of invariant subspacestext