### Planck-scale induced birefringence and CMB polarization data

Giulia Gubitosi

**Abstract:**

Some models of spacetime quantization 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. For the most studied model of quantum-spacetime-induced birefringence, characterized by a single length scale lambda, available BOOMERanG 2003 and WMAP data can be used to establish a bound of Planck-length significance lambda<0.41*10^-35 m. >