“Parity violation constraints from Planck CMB polarization data”
Abstract: Planck polarized CMB data is used constrain the cosmic birefringence effect, i.e. the in vacuo rotation of the photons polarization direction during propagation. In general the impact of such an effect, which is naturally parameterized by an angle α, consists in a mixing between Q and U stokes parameters that produces non-null CMB cross correlation between temperature and B mode-polarization, and between E- and B-mode polarization. This makes the cosmic birefringence effect a tracer of parity violating physics.