Guenakh Mitselmakher, Pierre Ramond, Neil Sullivan, David Tanner, Karl van Bibber
[en] axion ; quasar ; polarisation
[en] The observation of redshift-dependent coherent orientations of quasar polarisation vectors over cosmological distances in some regions of the sky is reviewed. Based on a good-quality sample of 355 measured quasars, this observation seems to infer the existence of a new effect acting on light propagation on such huge distances. A solution in terms of nearly massless axion-like particles has been proposed in the literature and its current status is discussed.