Generalized Dirac-Pauli equation and neutrino quantum states in matter

Starting with the Dirac-Pauli equation for a massive neutrino in an external magnetic field, we propose a new quantum equation for a neutrino in the presence of the background matter. On this basis the quantum theory of a neutrino moving in the background matter is developed: i) for the particular case of the matter with a constant density the exact solutions of this new equation are found and classified over the neutrino spin states, ii) the corresponding energy spectrum is also derived accounting for the neutrino helicity. Using these solutions we develop the quantum theory of the spin light of neutrino ($SL\nu$) in the matter. The $SL\nu$ radiation rate and total power are derived for different linear and circular polarizations of the emitted photons. Within the solid base of the developed quantum approach, the existence of the neutrino self-polarization effect in the matter is also shown.