CCAPP Seminar: "Exploring circular polarization in the CMB due to conventional sources of cosmic birefringence" Paulo Montero Camacho (OSU Physics)

June 13, 2018
Tuesday, July 17, 2018 - 11:30am to 12:30pm
PRB 4138
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The circular polarization of the Cosmic Microwave Background (CMB) is usually taken to be zero since it is not generated by Thomson scattering. In this talk I will discuss possible methods of generating circular polarization in the CMB due to propagation effects. I will only consider physics inside the Standard Model.  I will present two classes of mechanisms for birefringence: alignment of matter to produce an anisotropic susceptibility tensor, and anisotropy of the radiation field coupled to the non-linear response of the medium to electromagnetic fields;  this can occur either via photon-photon scattering (non-linear response of the vacuum); atomic hyperpolarizability (non-linear response of neutral atoms); or plasma delay (non-linear response of free electrons). The strongest effect comes from photon-photon scattering from recombination. Nevertheless, our results are consistent with a negligible circular polarization of the CMB in comparison with the linear polarization or the sensitivity of current and near-term experiments.

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