New Tests of the Equivalence Principle Using Non - Couplings of Electromagnetism and Gravitation.

Calculations are performed for the physical predictions made by theories of gravity that introduce non-metric couplings of gravitation to electromagnetism. These results are then compared with existing observations in order to place limits on the viability of describing the solar gravitational field by theories that employ an Algebraically Extended (AE) metric in the gravitational field equations. The prototypical AE theory used in these calculations is Moffat's Nonsymmetric Gravitation Theory (NGT). It is shown that a class of AE theories of gravity, which includes NGT, using a particular general form of coupling, predicts a polarization dependent speed of light. This leads directly to polarization dependent bending of light (gravitationally induced birefringence) and radar echo time delay. It also leads to an orientation dependence of the energy of certain atomic transitions. Finally, the theory predicts an observed depolarization of solar spectral lines near the limb of the Sun. The theoretical maximum of observable circular polarization is compared with observations of Stokes V for certain spectral lines. This comparison is used to place limits on the NGT contributions to gravitational physics in the solar system. The limits are weakly dependent on a parameter involved in modeling of the solar atmosphere. A highly conservative model gives limits approximately 70 times stronger than previous limits. A model using the best available estimate of the solar modeling parameter gives a limit that is three orders of magnitude tighter than previous limits.