Evolution of Mixed Dirac Particles Interacting with an External Magnetic Field

We study in the framework of relativistic quantum mechanics the evolution of a system of two Dirac neutrinos that mix with each other and have non-vanishing magnetic moments. The dynamics of this system in an external magnetic field is determined by solving the Pauli-Dirac equation with a given initial condition. We consider first neutrino spin-flavor oscillations in a constant magnetic field and derive an analytical expression for the transition probability of spin-flavor conversion in the limit of small magnetic interactions. We then investigate ultrarelativistic neutrinos in an transversal magnetic field and derive their wave functions and transition probabilities with no limitation for the size of transition magnetic moments. Although we consider neutrinos, our formalism is straightforwardly applicable to any spin-1/2 particles.Comment: 10 pages, 1 eps figure, RevTeX4; new appendix devoted to quantum mechanical treatment of neutrino spin-flavor oscillations was added; final variant to be published in Phys. Lett.

Neutrino spin oscillations in gravitational fields

We study neutrino spin oscillations in gravitational fields. The quasi-classical approach is used to describe the neutrino spin evolution. First we examine the case of a weak gravitational field. We obtain the effective Hamiltonian for the description of neutrino spin oscillations. We also receive the neutrino transition probability when a particle propagates in the gravitational field of a rotating massive object. Then we apply the general technique to the description of neutrino spin oscillations in the Schwarzschild metric. The neutrino spin evolution equation for the case of the neutrino motion in the vicinity of a black hole is obtained. The effective Hamiltonian and the transition probability are also derived. We examine the neutrino oscillations process on different circular orbits and analyze the frequencies of spin transitions. The validity of the quasi-classical approach is also considered.Comment: RevTeX4, 9 pages, 1 esp figure; article was revised, some misprints were corrected, 6 references added; accepted for publication in Int.J.Mod.Phys.

Relaxation of the chiral imbalance in dense matter of a neutron star

Using the quantum field theory methods, we calculate the helicity flip of an electron scattering off protons in dense matter of a neutron star. The influence of the electroweak interaction between electrons and background nucleons on the helicity flip is examined. We also derive the kinetic equation for the chiral imbalance. The derived kinetic equation is compared with the results obtained by other authors.Comment: 8 pages in pdflatex, EPJ Web of Conferences latex style; contribution to proceedings of Quarks-201

Attractive interaction between ions inside a quantum plasma structure

We construct the model of a quantum spherically symmetric plasma structure based on radial oscillations of ions. We suppose that ions are involved in ion-acoustic plasma oscillations. We find the exact solution of the Schr\"{o}dinger equation for an ion moving in the self-consistent oscillatory potential of an ion-acoustic wave. The system of ions is secondly quantized and its ground state is constructed. Then we consider the interaction between ions by the exchange of an acoustic wave. It is shown that this interaction can be attractive. We describe the formation of pairs of ions inside a plasma structure and demonstrate that such a plasmoid can exist in a dense astrophysical medium corresponding to the outer core of a neutron star.Comment: 17 pages, two columns, 3 figures, PDF LaTeX; paper was significantly revised, Appendix was shortened, new astrophysical application was discussed; version accepted for publication in J. Plasma Phy