TY  - JOUR
A1  - Drewes, Marco
A1  - Mendizabal, Sebastián
A1  - Weniger, Christoph
T1  - The Boltzmann equation from quantum field theory
T2  - Physics Letters B
N2  - 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.
Y1  - 2012
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/76923
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-769238
SN  - 0370-2693
VL  - 718.2013
IS  - 3
SP  - 1119
EP  - 1124
PB  - Elsevier
CY  - Amsterdam
ER  -