2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/228940The concept of definability of quantum fields in a set-theoretical foundation is introduced. We propose an axiomatic set theory and then derive a nonlinear sigma model and the Schroedinger equation in a Lagrangian form; this follows naturally from a null postulate which expresses symmetry of action. Definability in this theory is necessary and sufficient for quantum mechanics. Space-time proves to be relational and the fields are free of singularities9 pages. The axiom system has been simplifiedGeneral PhysicsHigh Energy Physics - Theorytext