Constraints on parity violation from the Cosmic Microwave Background
Parity violating extensions of the standard electromagnetism produce the cosmic birefringence effect, i.e. the in vacuo rotation of the linear polarization of the photons during their propagation. This effect, in its isotropic form, would generate a clear signature on the temperature and polarization anisotropies of the cosmic microwave background (CMB) and, in particular, it would switch on the TB and EB angular power spectra that otherwise would be null. We review the statistical methodologies developed to look for the isotropic birefringence effect and some recent results obtained using data from the ground based ACTpol experiment and from the Planck satellite. We also present forecasts on the ability of future CMB experiments to measure this effect.