Planck-scale lorentz invariance violations and CMB polarization data

Some models of spacetime quantization leading to violations of Lorentz symmetries predict a minute effect of birefringence for the propagation of photons. For Cosmic Microwave Background (CMB) photons, which have some degree of linear polarization, this results in a rotation of their polarization direction. The effect is greatly amplified by their long time of propagation, and could have observably large implications for analyses of CMB polarization. Here we mainly report the results of previous works1,2,3, in which it is shown that for the most studied model of quantum-spacetime-induced birefringence, available BOOMERanG 2003 and WMAP data can be used to establish a bound of Planck-scale significance. We give forecasts on the sensitivities achievable by future CMB polarization measures and we comment on how systematic effects of CMB experiments could influence these constraints. As a final point we discuss how Lorentz violations can also produce non-isotropic birefringence effects.