Photon-photon interactions as a source of cosmic microwave background circular polarization
R. F. Sawyer
Accepted
Photon-photon interactions mediated by the neutral hydrogen background can transform plane polarization into circular polarization, through completely forward processes, g+g+atom g+ g+atom, in which only the photon polarizations are changed. The ratio of circular to plane polarization intensities is predicted to be greater than 10-5 for some regions that have angular size less than .2.