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Is the Cosmic Microwave Background Circularly Polarized?

Asantha Cooray·Alessandro Melchiorri·Joseph Silk
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Abstract

The primordial anisotropies of the cosmic microwave background (CMB) are linearly polarized via Compton-scattering. The Faraday conversion process during the propagation of polarized CMB photons through regions of the large-scale structure containing magnetized relativistic plasma, such as galaxy clusters, will lead to a circularly polarized contribution. Though the resulting Stokes-V parameter is of order 10^-9 at frequencies of 10 GHz, the contribution can potentially reach the total Stokes-U at low frequencies due to the cubic dependence on the wavelength. In future, the detection of circular polarization of CMB can be used as a potential probe of the physical properties associated with relativistic particle populations in large-scale structures.

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Asantha Cooray, Alessandro Melchiorri, Joseph Silk. 2002-05-15. Is the Cosmic Microwave Background Circularly Polarized?. https://doi.org/10.1016/s0370-2693(02)03291-4

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