# Perturbative Dynamics of Open Quantum Systems by Renormalization Group Method

## TL;DR

This paper applies the renormalization group method to analyze the perturbative dynamics of open quantum systems, deriving a reduced dynamics approximation that aligns with quantum master equations and is validated against an exactly solvable model.

## Contribution

It introduces a novel application of the RG method to open quantum systems, providing long-time accurate solutions and a connection to quantum master equations.

## Key findings

- RG method eliminates secular terms in dynamics
- Reduced dynamics closely matches exact solutions
- Applicable to models like the spin-boson system

## Abstract

We analyze perturbative dynamics of a composite system consisting of a quantum mechanical system and an environment by the renormalization group (RG) method. The solution obtained from the RG method has no secular terms and approximates the exact solution for a long time interval. Moreover, the RG method causes a reduction of the dynamics of the composite system under some assumptions. We show that this reduced dynamics is closely related to a quantum master equation for the quantum mechanical system. Then, we compare this dynamics with the exact dynamics in an exactly solvable spin-boson model.