2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/64878We initiate a mathematically rigorous study of Klein-Gordon position operators in single-particle relativistic quantum mechanics. Although not self-adjoint, these operators have real spectrum and enjoy a limited form of spectral decomposition. The associated C*-algebras are identifiable as crossed products. We also introduce a variety of non self-adjoint operator algebras associated with the Klein-Gordon position representation; these algebras are commutative and continuously (but not homeomorphically) embeddable in corresponding function algebras. Several open problems are indicated.28 pagesOperator AlgebrasMathematical PhysicsFunctional Analysis47L30, 47L15; 81R15, 47L90, 46L52, 46J99text