Polar vs. apolar alignment in systems of polar self-propelled particles

TL;DR

This paper compares polar and apolar alignment mechanisms in self-propelled particles, highlighting their similarities in fluctuations and band formation, but also their key differences in symmetry and stability of ordered phases.

Contribution

It provides a comparative analysis of polar and apolar alignment, revealing fundamental differences in symmetry and stability despite shared features.

Findings

Both systems exhibit giant number fluctuations.

Both systems show self-segregation in the form of bands.

Differences include symmetry of the ordered phase and band stability.

Abstract

The symmetry of the alignment mechanism in systems of polar self-propelled particles determines the possible macroscopic large-scale patterns that can emerge. Here we compare polar and apolar alignment. These systems share some common features like giant number fluctuations in the ordered phase and self-segregation in the form of bands near the onset of orientational order. Despite these similarities, there are essential differences like the symmetry of the ordered phase and the stability of the bands.