New test of nonsymmetric theories of gravity: Observational limits on gravity-induced depolarization of solar spectral lines

We show that theories which couple the antisymmetric part of a nonsymmetric-tensor gravitational field to the electromagnetic field predict a depolarization of the Zeeman components of spectral lines emitted by extended, magnetically active regions near the limb of the Sun. This new effect is a consequence of the violation of the Einstein equivalence principle by these nonsymmetric alternatives to general relativity. We show that existing solar-physics data limit the extent of such depolarization and imply that the Sun's antisymmetric charge l_² must be less than (535 km)² in Moffat's theory, the prototypical nonsymmetric theory of gravity.