# Spin bath dynamics and dynamical Renormalization Group

## TL;DR

This paper investigates the quantum dynamics of the central spin model, comparing static and dynamic baths, and introduces a dynamical Renormalization Group method combined with equations of motion to analyze quantum correlations and secular terms.

## Contribution

It presents a novel analytical approach using dynamical Renormalization Group with equations of motion to better understand central spin dynamics and quantum correlations.

## Key findings

- Exact solution for static bath case
- dRG combined with equations of motion improves accuracy
- Separates classical non-linear behavior from quantum corrections

## Abstract

Abstract We discuss the quantum dynamics of the central spin model in a regime where the central spin and bath are slaved to each other. The exact solution is found when the bath is static, and is compared with the effect of an external field, finding that they are inequivalent due to the quantum nature of the environment. When the bath has dynamics, we analyze the differences between the numerical simulation using time-dependent perturbation theory and the equation of motion technique, which shows better accuracy. We demonstrate that the use of dynamical Renormalization Group (dRG), simultaneously with the equation of motion technique, provides a suitable analytical tool to understand the physics, to capture the main physical processes, and a powerful method to eliminate secular terms. In addition, this approach allows to separate classical non-linear behavior from corrections due to quantum correlations.