On time-dependent projectors and on generalization of thermodynamical approach to open quantum systems

TL;DR

This paper develops a perturbative method for deriving time-local master equations with time-dependent projectors, generalizing the Kawasaki--Gunton approach for open quantum systems.

Contribution

It introduces a novel perturbative technique for time-dependent projectors and generalizes the Kawasaki--Gunton projector for nonlinear master equations in open quantum systems.

Findings

Provides a consistent perturbative framework for time-dependent projectors.

Generalizes the Kawasaki--Gunton projector for broader applications.

Derives nonlinear master equations applicable to open quantum systems.

Abstract

In this paper, we develop a consistent perturbative technique for obtaining a time-local master equation based on projective methods in the case where the projector depends on time. We then introduce a generalization of the Kawasaki--Gunton projector, which allows us to use this technique to derive, generally speaking, nonlinear master equations in the case of arbitrary ansatzes consistent with some set of observables. Most of our results are very general, but in our discussion we focus on the application of these results to the theory of open quantum systems.