PROBING THE LIGHT SPEED ANISOTROPY WITH RESPECT TO THE COSMIC MICROWAVE BACKGROUND RADIATION DIPOLE

We have studied the angular fluctuations in the speedof lightwith respect to the apex of the dipole of Cosmic Microwave Background(CMB) radiation using the experimental data obtained with GRAAL facility, located at the European Synchrotron RadiationFacility (ESRF) in Grenoble. The measurements were based on the stability of the Compton edgeof laser photons scattered on the 6 GeV monochromaticelectron beam. The results enable one to obtain a conservative constraint on the anisotropy in the light speed variations Δc(θ)/c<3×10-12, i.e. with higher precision than from previous experiments.