From LRO to Disorder via QLRO in Spatially Inhomogeneous Polar Flock

TL;DR

This paper investigates how spatial inhomogeneities affect the collective motion of polar flocks in two dimensions, revealing a transition from long-range order to disorder as inhomogeneity increases.

Contribution

It introduces a model of inhomogeneous environments with random high-noise regions and analyzes the resulting phase transitions in flock behavior.

Findings

Transition from long-range to quasi-long-range order with increasing inhomogeneity

Order-disorder transition changes from discontinuous to continuous

Phase behavior resembles that in systems with physical disorder

Abstract

We study the collective behavior of a polar flock in an inhomogeneous environment in two-dimensions. The inhomogeneity is modelled by introducing regions at random locations on the substrate with higher noise but accessible for the flock to move. Hence inside such regions the particles orientation get randomised. Such inhomogeneities are different from the physical disorder, which obstructs the space for the incoming particles. The study focuses on how the phase behavior of polar flock changes by tuning the packing fraction of inhomogeneity. As packing fraction increases, the system crosses over from long-range to quasi long range order and ultimately to a disordered phase, while the order disorder transition for flocking changes from discontinuous to continuous. The resultant phase behavior of polar flock patterns here is comparable to that exhibited in the presence of physical disorder.