Joint constraint on primordial gravitational waves and polarization rotation angle with current CMB polarization data

Understand

Cosmological CPT violation will rotate the polarized direction of CMB photons, convert partial CMB E mode into B mode and vice versa.

• It will generate non-zero EB, TB spectra and change the EE, BB, TE spectra.
• This phenomenon gives us a way to detect the CPT-violation signature from CMB observations, and also provides a new mechanism to produce B mode polarization.
• In this paper, we perform a global analysis on tensor-to-scalar ratio $r$ and polarization rotation angles based on current CMB datasets with both low $\ell$ (Planck, BICEP2/Keck Array) and high $\ell$ (POLARBEAR, SPTpol, ACTPol).