期刊
PHYSICS LETTERS B
卷 718, 期 3, 页码 1119-1124出版社
ELSEVIER
DOI: 10.1016/j.physletb.2012.11.046
关键词
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资金
- Gottfried Wilhelm Leibniz programme of the Deutsche Forschungsgemeinschaft
- European Union FP7 ITN INVISIBLES (Marie Curie Actions) [PITN-GA-2011-289442]
We show from first principles the emergence of classical Boltzmann equations from relativistic nonequilibrium quantum field theory as described by the Kadanoff-Baym equations. Our method applies to a generic quantum field, coupled to a collection of background fields and sources, in a homogeneous and isotropic spacetime. The analysis is based on analytical solutions to the full Kadanoff-Baym equations, using the WKB approximation. This is in contrast to previous derivations of kinetic equations that rely on similar physical assumptions, but obtain approximate equations of motion from a gradient expansion in momentum space. We show that the system follows a generalized Boltzmann equation whenever the WKB approximation holds. The generalized Boltzmann equation, which includes off-shell transport, is valid far from equilibrium and in a time dependent background, such as the expanding universe. (C) 2012 Elsevier B.V. All rights reserved.
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