MAXWELL THEORY ON A POST-RIEMANNIAN SPACETIME AND THE EQUIVALENCE PRINCIPLE

The farm of Maxwell's theory is well known in the framework of general relativity, a fact that is related to the applicability of the princi ple of equivalence to electromagnetic phenomena. We pose the question whether this form changes if torsion and/or non-metricity fields are a llowed for in spacetime. Starting from the conservation laws of electr ic charge and magnetic flux, we recognize that the Maxwell equations t hemselves remain the same, but the constitutive law must depend on the metric and, additionally, may depend on quantities related to torsion and/or non-metricity. We illustrate our results by putting an electri c charge on top of a spherically symmetric exact solution of the metri c-affine gauge theory of gravity (which indicates torsion and non-metr icity). Ail this is compared to the recent results of Vaodyck.