http://arxiv.org/abs/1607.02094
Generation of magneto-optic effects by the cosmic microwave background (CMB) in the presence of cosmic magnetic fields is studied. Four mechanisms which generate polarization of the CMB such as the Cotton-Mouton effect, the vacuum polarization in external magnetic field, the photon-pseudoscalar mixing in external magnetic field and the Faraday effect are studied. Considering the CMB linearly polarized at decoupling time due to Thomson scattering, it is shown that second order effects in the magnetic field amplitude such as the Cotton-Mouton effect in plasma and the vacuum polarization (Euler-Heisenberg term) in cosmic magnetic field, would generate elliptic polarization of the CMB at post decoupling time depending on the photon frequency and magnetic field strength. The Cotton-Mouton effect in plasma turns out to be the dominant effect in the generation of CMB elliptic polarization in the low frequency part while the vacuum polarization in magnetic field is the dominant process in the high frequency part. The effect of pseudoscalar particles (axions and axion-like particles) on the CMB polarization is also studied. It is shown that photon-pseudoscalar particle mixing in cosmic magnetic field generates elliptic polarization of the CMB as well, depending on the circumstances and even in the case of initially unpolarized CMB. New limits on the pseudoscalar parameter space are set. Prior decoupling CMB polarization due to pseudoscalar particles is also discussed.
D. Ejlli
Fri, 8 Jul 16
5/56
Comments: 45 pages, 2 figures
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