Limits on Cosmological Birefringence from the Ultraviolet Polarization
  of Distant Radio Galaxies
  We report on an update of the test on the rotation of the plane of linear
polarization for light traveling over cosmological distances, using a
comparison between the measured direction of the UV polarization in 8 radio
galaxies at z>2 and the direction predicted by the model of scattering of
anisotropic nuclear radiation, which explains the polarization. No rotation is
detected within a few degrees for each galaxy and, if the rotation does not
depend on direction, then the all-sky-average rotation is constrained to be
\theta = -0.8 +/- 2.2. We discuss the relevance of this result for constraining
cosmological birefringence, when this is caused by the interaction with a
cosmological pseudo-scalar field or by the presence of a Cherns-Simons term.
