Irreversibility and emergent structure in active matter

Area of Science:

• Soft matter physics
• Non-equilibrium thermodynamics
• Active matter systems

Background:

• Active matter is a key paradigm for out-of-equilibrium soft matter.
• Collective phenomena like motility-induced phase separation and polar alignment are observed.
• The thermodynamics of these systems, particularly dynamical irreversibility, remain poorly understood.

Purpose of the Study:

• To investigate the dynamical irreversibility of large-scale active systems.
• To explore systems exhibiting motility-induced phase separation and polar alignment.
• To understand the thermodynamics of active matter, including microfeatures and defects.

Main Methods:

• Modeling active matter with translational and rotational degrees of freedom.
• Quantifying steady-state irreversibility across the phase diagram.
• Analyzing the role of time reversal symmetry in particle dynamics.

Main Results:

• A previously unreported hidden component in active matter dynamics was revealed.
• Sharp discontinuities in irreversibility were identified at phase transitions.
• Irreversibility was quantified for individual particles, enabling microfeature analysis.

Conclusions:

• The study provides a framework for understanding the thermodynamics of active matter.
• Dynamical irreversibility and its discontinuities are crucial at phase transitions.
• Interpreting time reversal symmetry is essential for active matter dynamics and thermodynamics.