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Fermion propagator in out of equilibrium quantum-field system and the Boltzmann equation

A. Niégawa
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Abstract

We aim to construct from first principles a perturbative framework for studying nonequilibrium quantum-field systems that include massless Dirac fermions. The system of our concern is quasiuniform system near equilibrium or nonequilibrium quasistationary system. We employ the closed-time-path formalism and use the so-called gradient approximation. Essentially no further approximation is introduced. We construct a fermion propagator, with which a well-defined perturbative framework is formulated. In the course of construction of the framework, we obtain the generalized Boltzmann equation (GBE) that describes the evolution of the number-density functions of (anti)fermionic quasiparticles.

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A. Niégawa. 2001-11-15. Fermion propagator in out of equilibrium quantum-field system and the Boltzmann equation. https://doi.org/10.1103/physrevd.65.056009

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