# Thermodynamics of emergent structure in active matter

## TL;DR

This paper investigates the nonequilibrium thermodynamics of active matter systems, revealing how entropy production varies across phases and identifying thermodynamic signatures of phase transitions and micro-structural features.

## Contribution

It introduces a fully under-damped model for active matter, uncovering hidden entropy productions and analyzing their relation to phase behavior and structural defects.

## Key findings

- Discontinuous entropy production at phase transitions
- Identification of dissipation rates for different phases
- Entropy production linked to micro-structural features like defects

## Abstract

Active matter is rapidly becoming a key paradigm of out-of-equilibrium soft matter exhibiting complex collective phenomena, yet the thermodynamics of such systems remain poorly understood. In this letter we study the nonequilbrium thermodynamics of large scale active systems capable of mobility-induced phase separation and polar alignment, using a fully under-damped model which exhibits hidden entropy productions not previously reported in the literature. We quantify steady state entropy production at each point in the phase diagram, revealing characteristic dissipation rates associated with the distinct phases and configurational structure. This reveals sharp discontinuities in the entropy production at phase transitions and facilitates identification of the thermodynamics of micro-features, such as defects in the emergent structure. The interpretation of the time reversal symmetry in the dynamics of the particles is found to be crucial.