# Effective equilibrium states in the colored-noise model for active matter II. A unified framework for phase equilibria, structure and mechanical properties

## TL;DR

This paper develops a unified theoretical framework for understanding phase behavior, structure, and mechanical properties of active matter driven by colored noise, highlighting discrepancies between thermodynamic and mechanical measurements.

## Contribution

It introduces a dynamical density functional theory that links effective interactions with mechanical quantities in active matter systems.

## Key findings

- Mechanical pressure may be unequal in coexisting phases.
- Interfacial tension can become negative.
- Thermodynamic pressure does not always match mechanical pressure.

## Abstract

Active particles driven by colored noise can be approximately mapped onto a system that obeys detailed balance. The effective interactions which can be derived for such a system allow to describe the structure and phase behavior of the active fluid by means of an effective free energy. In this paper we explain why the related thermodynamic results for pressure and interfacial tension do not represent the results one would measure mechanically. We derive a dynamical density functional theory, which in the steady state simultaneously validates the use of effective interactions and provides access to mechanical quantities. Our calculations suggest that in the colored-noise model the mechanical pressure in coexisting phases might be unequal and the interfacial tension can become negative.