# Perturbative calculation of field space entanglement entropy

## TL;DR

This paper introduces a perturbative method to compute entanglement entropy between interacting quantum fields, addressing divergence issues in previous approaches and demonstrating the method on a two scalar field example.

## Contribution

It provides a novel perturbative framework for calculating field space entanglement entropy and resolves divergence problems caused by improper series truncation.

## Key findings

- The divergence in previous perturbative calculations is due to improper series truncation.
- The proposed method successfully computes entanglement entropy in a two scalar field model.
- The approach offers a systematic way to handle similar calculations in quantum field theories.

## Abstract

We present a general method for the perturbative calculation of the entanglement entropy between two interacting quantum fields. Previous attempts at calculating this quantity perturbatively have encountered a seemingly pathological divergence; we explain why this divergence is a result of improperly truncating a series expansion and give a prescription for avoiding this problem. We then apply our method to a simple example of two mass-mixing scalar fields.