Generalized Proca action for an Abelian vector field
  We revisit the most general theory for a massive vector field with derivative
self-interactions, extending previous works on the subject to account for terms
having trivial total derivative interactions for the longitudinal mode. In the
flat spacetime (Minkowski) case, we obtain all the possible terms containing
products of up to five first-order derivatives of the vector field, and provide
a conjecture about higher-order terms. Rendering the metric dynamical, we
covariantize the results and add all possible terms implying curvature.
