Can primordial parity violation explain the observed cosmic birefringence?

Recently, the cross-correlation between E- and B-mode polarization of the cosmic microwave background, which is well explained by cosmic birefringence with rotation angle beta approximate to 0.3 deg, has been found in cosmic microwave background polarization data. We carefully investigate the possibility of explaining the observed EB correlation by the primordial chiral gravitational waves, which can be generated in the parity-violating theories in the primordial Universe. We found that the chiral gravitational wave scenario does not work due to the overproduction of the BB autocorrelation, which far exceeds the observed one by SPTPol and POLARBEAR.

Automated summary

Recently, the cross-correlation between E- and B-mode polarization of the cosmic microwave background has been found, and it can be explained by cosmic birefringence with a rotation angle of approximately 0.3 degrees. However, further investigation shows that this explanation fails to account for the observed EB correlation due to the excessive production of BB autocorrelation.