Radiative transfer for polarized radiation: symmetry properties and geometrical interpretation

The general properties of the transfer equations for polarized radiation are discussed in detail and some relevant symmetries about the absorption matrix and the emission vector are deduced. A geometrical picture of the process of radiative transfer for polarized radiation is given by generalizing the model of the Poincare sphere. An ''electromagnetic analogy'' is achieved and it is then applied to the solution of some particular problems relevant in the process of line formation in a magnetic field. (author)