Large-scale coherent orientations of quasar polarisation vectors: interpretation in terms of axion-like particles

Abstract

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.

Replaced because of a previously badly displayed caption. Contributed to "Axions 2010", Gainesville (FL), January 15-17 2010. To be published in AIP conference series. 6 pages