Journalartikel

Jahr der Veröffentlichung: 1998

Seiten: 328-390

Zeitschrift: Annals of Physics

Bandnummer: 270

Heftnummer: 2

ISSN: 0003-4916

eISSN: 1096-035X

Open Access Status: Green

DOI Link: https://doi.org/10.1006/aphy.1998.5849

Verlag: Elsevier Masson

Abstract: 
We study stochastic aspects inherent to the (non-)equilibrium real time Green's function description (or "closed time path Green's function"-CTPGF) of transport equations, the so-called "Kadanoff-Baym equations." We couple a free scalar boson quantum field to an environmental heat bath with some given temperature T. It will be shown hr detail that the emerging transport equations have to be understood as the ensemble average over stochastic equations of Langevin type. This corresponds to the equivalence of the influence functional approach by Feynman and Vernon and the CTP technique. The former, however, gives a more intuitive physical picture. In particular the physical role of (quantum) noise and the connection of its correlation kernel to the Kadanoff-Baym equations will be discussed in depth. The inherent presence of noise and dissipation related by the fluctuation-dissipation theorem guarantees that the modes or particles become thermally populated on average in the long-time limit. For long wavelength modes with momenta \k\ much less than T the emerging wave equations behave nearly as classical fields. On the other hand, a kinetic transport description can be obtained in the semi-classical particle regime. Including fluctuations, its form resembles that of a phenomenological Boltzmann-Langevin description. However, we will point out some severe discrepancies in comparison to the Boltzmann Langevin scheme. As a Further byproduct we also note how the occurrence of so called pinch singularities is circumvented by a clear physical necessity of damping within the one-particle propagator. (C) 1998 Academic Press.

Harvard-Zitierstil: Greiner, C. and Leupold, S. (1998) Stochastic interpretation of Kadanoff-Baym equations and their relation to Langevin processes, Annals of Physics, 270(2), pp. 328-390. https://doi.org/10.1006/aphy.1998.5849

APA-Zitierstil: Greiner, C., & Leupold, S. (1998). Stochastic interpretation of Kadanoff-Baym equations and their relation to Langevin processes. Annals of Physics. 270(2), 328-390. https://doi.org/10.1006/aphy.1998.5849