Non equilibrium dynamics of mixing, oscillations and equilibration: a model study

Abstract

The non-equilibrium dynamics of mixing, oscillations and equilibration is studied in a field theory of flavored neutral mesons that effectively models two flavors of mixed neutrinos, in interaction with other mesons that represent a thermal bath of hadrons or quarks and charged leptons. This model describes the general features of neutrino mixing and relaxation via charged currents in a medium. The reduced density matrix and the non-equilibrium effective action that describes the propagation of neutrinos is obtained by integrating out the bath degrees of freedom. We obtain the dispersion relations, mixing angles and relaxation rates of ``neutrino'' quasiparticles. The dispersion relations and mixing angles are of the same form as those of neutrinos in the medium, and the relaxation rates are given by ${\Gamma }_1(k)={\Gamma }_{ee}(k){\cos }^2{\theta }_m(k)+{\Gamma }_{\mu \mu }(k){\sin }^2{\theta }_m(k);{\Gamma }_2(k)={\Gamma }_{\mu \mu }(k){\cos }^2{\theta }_m(k)+{\Gamma }_{ee}(k){\sin }^2{\theta }_m(k)$ where ${\Gamma }_{\alpha \alpha }(k)$ are the relaxation rates of the flavor fields in \emph{absence} of mixing, and ${\theta }_m(k)$ is the mixing angle in the medium. A Weisskopf-Wigner approximation that describes the asymptotic time evolution in terms of a non-hermitian Hamiltonian is derived. At long time $>>{\Gamma }_{1,2}^{-1}$ ``neutrinos'' equilibrate with the bath. The equilibrium density matrix is nearly diagonal in the basis of eigenstates of an \emph{effective Hamiltonian that includes self-energy corrections in the medium}. The equilibration of ``sterile neutrinos'' via active-sterile mixing is discussed.

28 pages, 3 figures, version to appear in PRD

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Cited by in corpus (10)

• Constraints on dark matter particles from theory, galaxy observations and N-body simulations
• Kadanoff-Baym Approach to Flavour Mixing and Oscillations in Resonant Leptogenesis
• Sterile Neutrino-Enhanced Supernova Explosions
• Perturbative Non-Equilibrium Thermal Field Theory
• Sterile neutrino production via active-sterile oscillations: the quantum Zeno effect
• Lepton asymmetry from mixing and oscillations
• Free streaming in mixed dark matter
• Production of a sterile species via active-sterile mixing: an exactly solvable model
• Unparticle-Higgs Mixing: MSW Resonances, See-saw Mechanism and Spinodal Instabilities
• Production of a sterile species: quantum kinetics