  We investigate the effects of pseudoscalar-photon mixing on electromagnetic
radiation in the presence of correlated extragalactic magnetic fields. We model
the Universe as a collection of magnetic domains and study the propagation of
radiation through them. This leads to correlations between Stokes parameters
over large scales and consistently explains the observed large-scale alignment
of quasar polarizations at different redshifts within the framework of the big
bang model.
