Generation of Circular Polarization of CMB via Polarized Compton
  Scattering
  The standard scenario of cosmology predicts a measurable amount for linear
polarization of the Cosmic Microwave Background radiation (CMB) via Thomson
scattering, while through this scenario, the generation of circular
polarization is excluded. On the another hand, the circular polarization of CMB
has not been excluded in observational evidence. The generation of CMB photons
circular polarization via their Compton scattering with polarized cosmic
electrons is considered in this paper. Our motivation for considering polarized
Compton scattering comes from the effects of the external magnetic field in
large scale, the chiral magnetic instability and new physics interactions of
the cosmic electrons. It is shown that damping term of polarized Compton
scattering in the presence of scalar perturbation can generate circular
polarization in CMB radiation, so that the power spectrum of circular
polarization of CMB $C_l^{V(S)}$ is proportional to the power spectrum of
temperature anisotropy of CMB $C_l^{I(S)}$ and also $\delta^2$ which is a
fraction of polarized electron number density to the total one with net Left-
or Right-handed polarizations. We have discussed that at least we need
$\delta<10^{-4}$ to find consistency with a reported upper limit of CMB
circular polarization.
