Abstract
Within the gauge symmetry framework, the U-1 symmetry of electrodynamics is violated in the presence of gravity with spacetime translational gauge symmetry in inertial frames. For a light ray, an eikonal equation with effective metric tensors is derived in the geometric-optics limit. Under these conditions, the angle of the deflection of light by the sun is calculated to be delta phi approximate to 1.75 '' in inertial frames without requiring a gauge condition such as partial derivative(mu)A(mu) = 0. In contrast, if the theory is U-1 gauge invariant, one can impose the gauge condition partial derivative(mu)A(mu) = 0 in the derivation of the eikonal equation. In this case, one obtains a slightly different effective metric tensor and a different angle of deflection oct) delta phi approximate to 1.52 ''. However, because the precision of experiments in the last century using optical frequencies has been no better than (10-20)% due to large systematic errors, one cannot unambiguously rule out the result delta phi approximate to 1.52'. We hope that the precision of these data can be improved in order to test Yang-Mills gravity.