Comment on "Flocking without Alignment Interactions in Attractive Active Brownian Particles [arXiv:2303.07746]"

TL;DR

This paper critiques a recent claim that attractive active Brownian particles can exhibit flocking without alignment, arguing that the observed phenomena do not meet the key criteria of true flocking behavior.

Contribution

It clarifies that the phenomena reported in the referenced study do not exhibit essential features of flocking, challenging the interpretation of those results.

Findings

Lack of long-range correlations in the observed phenomena

Absence of large-scale directed motion

Phenomenology does not meet flocking criteria

Abstract

In a recent Letter, Caprini and L\"owen argue that attractive active Brownian particles can flock even in the absence of explicit aligning interactions of their velocities. In this comment, I show that the phenomenology described in [Phys. Rev. Lett. {\bf 130}, 148202 (2023)] in fact lacks several defining features of flocking, such as long-range correlations and large-scale directed motion.