# Effective field theory out of equilibrium: Brownian quantum fields

@article{Boyanovsky2015EffectiveFT, title={Effective field theory out of equilibrium: Brownian quantum fields}, author={Daniel Boyanovsky}, journal={New Journal of Physics}, year={2015}, volume={17} }

The emergence of an effective field theory out of equilibrium is studied in the case in which a light field—the system—interacts with very heavy fields in a finite temperature bath. We obtain the reduced density matrix for the light field, its time evolution is determined by an effective action that includes the influence action from correlations of the heavy degrees of freedom. The non-equilibrium effective field theory yields a Langevin equation of motion for the light field in terms of…

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