Tuning attraction and repulsion between active particles through persistence

TL;DR

This paper investigates how the persistence of active particles influences their effective attraction or repulsion through recoil interactions, revealing a transition from repulsion to attraction at intermediate persistence lengths.

Contribution

It introduces a model linking persistence and recoil interactions, showing how persistence length can switch collective behavior from repulsive to attractive.

Findings

Highly persistent particles can switch from repulsive to attractive interactions.

A transition occurs at intermediate persistence lengths due to advective effects.

Active particles can modulate collective interactions by adjusting persistence.

Abstract

We consider the interplay between persistent motion, which is a generic property of active particles, and a recoil interaction which causes particles to jump apart on contact. The recoil interaction exemplifies an active contact interaction between particles, which is inelastic and is generated by the active nature of the constituents. It is inspired by the `shock' dynamics of certain microorganisms, such as \emph{Pyramimonas octopus}, and always generates an effective repulsion between a pair of passive particles. Highly persistent particles can be attractive or repulsive, according to the shape of the recoil distribution. We show that the repulsive case admits an unexpected transition to attraction at intermediate persistence lengths, that originates in the advective effects of persistence. This allows active particles to fundamentally change the collective effect of active interactions amongst them, by varying their persistence length.