Cosmological birefringence constraints from CMB and astrophysical   polarization data
  Cosmological birefringence is a rotation of the polarization plane of photons coming from sources of astrophysical and cosmological origin. The rotation can also depend on the energy of the photons and not only on the distance of the source and on the cosmological evolution of the underlying theoretical model. In this work, we constrain few selected models for cosmological birefringence, combining CMB and astrophysical data at radio, optical, X and gamma wavelengths, taking into account the specific energy and distance dependences. 
M. Galaverni, G. Gubitosi, F. Paci and F. Finelli
astro-ph.CO