# Production of a sterile species: quantum kinetics

Source: [Production of a sterile species: quantum kinetics](<https://www.sota2.com/research/paper/68fa22b27a2b558e2933d467>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-28T13:52:21.436Z

Authors: D. Boyanovsky, C.M.Ho

Published: 2007-05-04T20:31:40.000Z

## Abstract

Production of a sterile species is studied within an effective model of active-sterile neutrino mixing in a medium in thermal equilibrium. The quantum kinetic equations for the distribution functions and coherences are obtained from two independent methods: the effective action and the quantum master equation. The decoherence time scale for active-sterile oscillations is $\\tau\_{dec} = 2/\\Gamma\_{aa}$, but the evolution of the distribution functions is determined by the two different time scales associated with the damping rates of the quasiparticle modes in the medium: $\\Gamma\_1=\\Gamma\_{aa}\\cos^2\\tm ; \\Gamma\_2=\\Gamma\_{aa}\\sin^2\\tm$ where $\\Gamma\_{aa}$ is the interaction rate of the active species in absence of mixing and $\\tm$ the mixing angle in the medium. These two time scales are widely different away from MSW resonances and preclude the kinetic description of active-sterile production in terms of a simple rate equation. We give the complete set of quantum kinetic equations for the active and sterile populations and coherences and discuss in detail the various approximations. A generalization of the active-sterile transition probability \\emph{in a medium} is provided via the quantum master equation. We derive explicitly the usual quantum kinetic equations in terms of the \`\`polarization vector'' and show their equivalence to those obtained from the quantum master equation and effective action.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/0705.0703>)

[PDF](<https://arxiv.org/pdf/0705.0703.pdf>)