Definability in Physics
  The 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 singularities 
D.J. Bendaniel