New Photon Propagators in Quantum Electrodynamics
  A Lagrangian for quantum electrodynamics is found which makes it explicit that the photon mass is eventually set to zero in the physical part on observational ground. It remains possible to obtain a counterterm Lagrangian where the only non-gauge-invariant term is proportional to the squared divergence of the potential, while the photon propagator in momentum space falls off like the inverse squared power of k at large k, which indeed agrees with perturbative renormalizability. The resulting radiative corrections to the Coulomb potential in QED are also shown to be gauge-independent. A fundamental role of the space of four-vectors with components given by four-by-four matrices is therefore suggested by our scheme, where such matrices can be used to define a single gauge-fixing function in the functional integral. 
Giampiero Esposito