Testing Spacetime Symmetries with CMB polarization data
Gubitosi, Giulia (UC Berkeley, LBL, Berkeley, CA and PCCP APC Lab Univ. Paris Diderot)

Lorentz symmetry violations are expected to emerge when spacetime is probed on very short distance scales, of the order of the Planck length scale $\ell_P\sim10^{-35}m$. CMB photons provide a way to test spacetime on these very small scales thanks to their very long propagation time, that amplifies the anomalies of light behavior due to the breakdown of classical symmetries. These kind of anomalies would show up as a birefringent behavior of light (rotation of the polarization direction during propagation), which can depend on the direction of propagation if space isotropy is also violated. We show that polarization data gathered by the PLANCK satellite will reach the sensitivity required to test spacetime symmetries up to the Planck-scale, and that in particular the availability of a full-sky coverage can allow to perform also accurate tests on non-isotropic birefringence effects.