PUB - Publikationen an der Universität Bielefeld

The Einstein equivalence principle is certainly a key element in the development of new enhanced theories of gravity. Although being an important building block in Einstein's general relativity, theoretically predicted violations of its validity are a main feature in alternative, nonmetric gravitation theories if they are able to incorporate quantum mechanical principles. I have investigated metric-affine gauge theories of gravity which predict that a gravitational field singles out an orthogonal pair of polarization states of light that propagate with different phase velocities. This gravity-induced birefringence implies that propagation through a gravitational field can alter the polarization of light and so violates the Einstein equivalence principle. I use solar and white dwarf polarimetric data to constrain birefringence induced by the gravitational field of these objects and set limits on coupling constants required by such theories.