Collective Motion of Self-Propelled Particles with Memory

TL;DR

This paper demonstrates that incorporating memory through underdamped angular dynamics in self-propelled particle models leads to novel collective phases like vortex lattices and active foams, expanding understanding of active matter behavior.

Contribution

It introduces a Vicsek-style model with angular velocity memory, revealing new collective phases and explaining vortex lattice formation through effective interactions.

Findings

Discovery of vortex lattices and active foams in models with angular memory.

Observation of smectic Vicsek waves with nematic interactions leading to polar order.

Calculation of vortex interactions explaining lattice structures.

Abstract

We show that memory, in the form of underdamped angular dynamics, is a crucial ingredient for the collective properties of self-propelled particles. Using Vicsek-style models with an Ornstein-Uhlenbeck process acting on angular velocity, we uncover a rich variety of collective phases not observed in usual overdamped systems, including vortex lattices and active foams. In a model with strictly nematic interactions the smectic arrangement of Vicsek waves giving rise to global polar order is observed. We also provide a calculation of the effective interaction between vortices in the case where a telegraphic noise process is at play, explaining thus the emergence and structure of the vortex lattices observed here and in motility assay experiments.