A Hypothetical Effect of the Maxwell–Proca Electromagnetic Stresses on Galaxy Rotation Curves

Abstract

Abstract Maxwell–Proca electrodynamics corresponding to finite photon mass causes a substantial change in the Maxwell stress tensor, and under certain circumstances, may cause electromagnetic stresses to act effectively as “negative pressure.” This paper describes a model where this negative pressure imitates gravitational pull and may produce forces comparable to gravity and may even become dominant. The effect is associated with random magnetic fields with correlation lengths exceeding the photon Compton wavelength. The stresses act predominantly on the interstellar gas and cause an additional force pulling the gas toward the center and toward the galactic plane. Stars do not experience any significant direct force but get involved in this process via a “recycling loop,” where rapidly evolving massive stars are formed from the gas undergoing galactic rotation and then lose their mass back to the gas within a time shorter than roughly 1/6 of the rotation period. This makes their dynamics inseparable from that of the rotating gas. As soon as the lighter, slowly evolving stars are formed, they lose their connection to the gas and are only gravitationally confined within the galaxy. Peculiarities in the dynamics of these slowly evolving stars may serve as an experimental test of the presence and magnitude of the Maxwell–Proca stresses. In fact, observational data for Sun-like stars in our galaxy appear to be incompatible with the assumption of the Maxwell–Proca stresses contributing at a level needed to explain the galactic rotation curve, although they could contribute a 10%–20% addition to the observed centripetal pull. It may be interesting to also explore possible broader cosmological implications of the negative-pressure model.