Nonreciprocal yet Symmetric Multi-Species Active Matter: Emergence of Chirality and Species Separation

TL;DR

This paper introduces a multi-species active matter model with symmetric nonreciprocal interactions, leading to diverse collective behaviors such as chirality and species separation, driven by interplay between nonreciprocity and symmetry.

Contribution

It presents a novel symmetric nonreciprocal active matter model based on phase-shifted velocity alignment, revealing new collective phases and behaviors.

Findings

Discovery of a species-mixed chiral phase with quasi-long-range order

Identification of a species separation phase with vortex structures

Observation of a coexistence phase with dynamic pattern formation

Abstract

Nonreciprocal active matter systems typically feature an asymmetric role among interacting agents, such as a pursuer-evader relationship. We propose a multi-species nonreciprocal active matter model that is invariant under permutations of the particle species. The nonreciprocal, yet symmetric, interactions emerge from a constant phase shift in the velocity alignment interactions, rather than from an asymmetric coupling matrix. This system possessing permutation symmetry displays rich collective behaviors, including a species-mixed chiral phase with quasi-long-range polar order and a species separation phase characterized by vortex cells. The system also displays a coexistence phase of the chiral and the species separation phases, in which intriguing dynamic patterns emerge. These rich collective behaviors are a consequence of the interplay between nonreciprocity and permutation symmetry.