Can Quasars be Explained by Cosmological Waveguide Effects?

A sort of gravitational waveguide effect in cosmology could explain, in principle, the huge luminosities coming from quasars using the cosmological large scale structures as selfoc--type or planar waveguides. Furthermore, other anomalous phenomena connected with quasars, as the existence of "brothers" or "twins" objects having different brilliancy but similar spectra and redshifts, placed on the sky with large angular distance, could be explained by this effect. We describe the gravitational waveguide theory and then we discuss possible realizations in cosmology.