Circular dichroism, magnetic knots and the spectropolarimetry of the
  Cosmic Microwave Background
  When the last electron-photon scattering takes place in a magnetized
environment, the degree of circular polarization of the outgoing radiation
depends upon the magnetic field strength. After deriving the scattering matrix
of the process, the generalized radiative transfer equations are deduced in the
presence of the relativistic fluctuations of the geometry and for all the four
brightness perturbations. The new system of equations is solved under the
assumption that the incident radiation is not polarized. The induced V-mode
polarization is analyzed both analytically and numerically. The corresponding
angular power spectra are calculated and compared with the measured (or
purported) values of the linear polarizations (i.e. E-mode and B-mode) as they
arise in the concordance model and in its neighboring extensions. Possible
connections between the V-mode polarization of the Cosmic Microwave background
and the topological properties of the magnetic flux lines prior to equality are
outlined and briefly explored in analogy with the physics of magnetized sun
spots.
