Transitions driven by multibody interactions in an effective model of active matter

TL;DR

This paper investigates how multibody interactions influence phase transitions in active matter, using a high-dimensional approximation to reveal phenomena like motility-induced phase separation and a novel liquid-liquid transition.

Contribution

It demonstrates that multibody interactions are essential for understanding phase behavior in active particles, introducing a theoretical framework that captures complex collective phenomena.

Findings

Revealed a MIPS-like first order transition in the model.

Identified a new liquid-liquid transition at lower persistence times.

Linked the liquid-liquid transition to a spin glass phase of orientational degrees of freedom.

Abstract

When out-of-equilibrium particles interact by means of pairwise forces, their stationary distribution in general exhibits many-body interactions. In the particular case of active particles, it has been shown numerically that the Motility Induced Phase Separation cannot be explained by the effective attraction emerging from two isolated particles, thereby highlighting the role of multibody interactions. In this work, we study the thermodynamics of the Fox-UCNA approximation for active particles interacting by means of pairwise repulsive forces. Working at large space dimension we establish that multibody interactions up to infinite order are instrumental in giving rise to such collective phenomena as phase transitions. We recover a MIPS-like first order transition, but also find a liquid-liquid transition at somewhat lower persistence times. This new transition is connected to a spin glass phase of orientational-like degrees of freedom with disordered interactions set by the particle positions themselves.