# Entanglement contour and modular flow from subset entanglement entropies

## TL;DR

This paper investigates the entanglement contour and modular flow in two-dimensional theories, validating a partial entanglement entropy proposal, extending holographic analysis to BTZ black holes, and providing a new method to derive modular flows from entanglement entropies.

## Contribution

It confirms the validity of the partial entanglement entropy proposal and extends the entanglement contour analysis to BTZ black holes, offering a new approach to generate modular flows.

## Key findings

- Partial entanglement entropy satisfies all proposed rational requirements.
- Extended entanglement contour analysis from vacuum AdS to BTZ black holes.
- Provided a simple prescription to derive modular flows from entanglement entropies.

## Abstract

The Entanglement contour function quantifies the contribution from each degree of freedom in a region $\mathcal{A}$ to the entanglement entropy $S_{\mathcal{A}}$. Recently in \cite{Wen:2018whg} the author gave two proposals for the entanglement contour in two-dimensional theories. The first proposal is a fine structure analysis of the entanglement wedge which applies to holographic theories. The second proposal is a claim that for general two-dimensional theories the partial entanglement entropy is given by a linear combination of entanglement entropies of relevant subsets inside $\mathcal{A}$. In this paper we further study the partial entanglement entropy proposal by showing that it satisfies all the rational requirements proposed previously. We also extend the fine structure analysis from vacuum AdS space to BTZ black holes. Furthermore we give a simple prescription to generate the local modular flows for two-dimensional theories from only the entanglement entropies without refer to the explicit Rindler transformations.