Electrodynamics and gravitational effects of Proca stresses in astrophysics

If the photon were to have a rest mass near the best present upper limit, m < approximately 3x10-53g, Maxwell's equations would be inapplicable over distances exceeding about 1015 cm, with profound implications for cosmic electrodynamics. This paper deals with electrodynamic and gravitational effects of the non-Maxwellian stresses which would be associated with large-scale magnetic fields in quasi-static plasmas in these circumstances. The existence of moderately dense interstellar gas clouds with relatively strong magnetization shows that m < approximately 10-58 g. General relativity must be used to calculate even the 'Newtonian' gravitational effects of electromagnetic fields, and it is shown here that the Newtonian potential caused by the non-Maxwellian stresses just cancels that caused by the non-Maxwellian energy density. Previous arguments based on the latter alone are therefore invalid. (Auth.)