Improved constraints on cosmic birefringence from the WMAP and Planck cosmic microwave background polarization data

The observed pattern of linear polarization of the cosmic microwave background photons is a sensitive probe of physics violating parity symmetry under inversion of spatial coordinates. A new parity-violating interaction might have rotated the plane of linear polarization by an angle ss as the cosmic microwave background photons have been traveling for more than 13 billion years. This effect is known as cosmic birefringence. In this paper, we present new measurements of cosmic birefringence from a joint analysis of polarization data from two space missions, Planck and WMAP. This dataset covers a wide range of frequencies from 23 to 353 GHz. We measure ss = 0.342 degrees(+0.094 degrees)(-0.091 degrees) [68% confidence level (CL)] for nearly full-sky data, which excludes ss = 0 at 99.987% CL. This corresponds to the statistical significance of 3.6s. There is no evidence for frequency dependence of ss. We find a similar result, albeit with a larger uncertainty, when removing the Galactic plane from the analysis.

Automated summary

In this study, new measurements of cosmic birefringence are presented from a joint analysis of polarization data from the Planck and WMAP space missions. The results show that the plane of linear polarization of cosmic microwave background photons may have rotated during their 13 billion-year journey, with no evidence of frequency dependence. This finding has significant implications for the study of physics violating parity symmetry.