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Fluctuation-dissipation relation from the nonequilibrium dynamics of a nonlinear open quantum system

TitleFluctuation-dissipation relation from the nonequilibrium dynamics of a nonlinear open quantum system
Publication TypeJournal Article
Year of Publication2020
AuthorsJ-T. Hsiang, and B-L. Hu
JournalPhys. Rev. D
Volume101
Date Publishedjun
ISSN1550-7998
Abstract

Continuing our inquiry into the conditions when fluctuation-dissipation relations (FDR) may appear in the context of nonequilibrium dynamics of open quantum systems (over and beyond the conventional FDR from linear response theory) we turn to non-Gaussian systems and consider this issue for an anharmonic quantum oscillator interacting with a scalar quantum field bath. We present the general nonperturbative expressions for the rate of energy (power) exchange between the anharmonic oscillator and its thermal bath. For the cases that a stable final equilibrium state exists, and the nonstationary components of the two-point functions of the anharmonic oscillator have negligible contributions to the power balance, we can show nonperturbatively that equilibration implies an FDR for the anharmonic oscillator. We then use a weakly anharmonic oscillator as an example to illustrate the validity of those two assumptions and show that in the weak anhamonicity limit, they are satisfied according to our first-order perturbative results..

DOI10.1103/PhysRevD.101.125003