Abstract
We have studied in this work extended electrodynamics with a relaxed Lorenz gauge condition. We then compare it with the electrodynamics in curved space–time. Interestingly, the interaction of the electromagnetic field with the space curvature induces electric and magnetic charges and currents. The coupling of the electromagnetic field with the particle charge gives rise to its spin. Two spins are found to emerge in addition to their associated helicities. The electromagnetic field is found to be coupled to curvature through its electric and magnetic spins. The electrodynamics in curved space is found to be analogous to massive electrodynamics. When the electromagnetic field travels in curved space–time, it acquires mass depending on the strength of the space curvature. In curved space, the space in which the electromagnetic field travels got an effective electric conductivity proportional to the temporal variation of the metric determinant. The curved space appears to behave like a conducting medium with variable electric conductivity. Moreover, an additional current perpendicular to the magnetic field is induced whenever the space is curved. Axion and Chern–Simons electrodynamics are found to be connected to massive electrodynamics and standard electrodynamics in curved space–time.