Non-Lagrangian gauge field models are physically excluded

Abstract

While non-action-generated, but identically conserved, abelian/YM gauge vectors exist, they are unsuitable for building alternate field equations, because they have no stress-tensor, hence do not permit Poincare generators and, most physically, cannot consistently couple to gravity. Separately, their geometric analogues, covariantly conserved non-Lagrangian symmetric tensors, probably do not even exist, but their weak field, abelian, counterparts do, and share the vector fields’ absence of generators.