Topologically induced swarming phase transition on a 2D percolated lattice

Abstract

The emergence of collective motion, or swarming, in groups of moving individuals who orient themselves using only information from their neighbors is a very general phenomenon that occurs at multiple spatio-temporal scales. Swarms that occur in natural environments typically have to contend with spatial disorder such as obstacles that can hinder an individual's motion or can disrupt communication with neighbors. We study swarming agents, possessing both aligning and mutually avoiding repulsive interactions, in a 2D percolated network representing a topologically disordered environment. We numerically find a phase transition from a collectively moving swarm to a disordered gas-like state above a critical value of the topological or environmental disorder. For agents that utilize only alignment interactions, we find that the swarming transition does not exist in the large system size limit, while the addition of a mutually repulsive interaction can restore the existence of the transition at a finite critical value of disorder. We find there is a finite range of topological disorder where swarming can occur and that this range can be maximized by an optimal amount of mutual repulsion.

Avalanche dynamics for active matter in heterogeneous media

“…It would also be interesting to determine whether other active matter models such as flocking particles exhibit avalanche behavior in the presence of quenched disorder. Simulations have already shown nonmonotonic transport behavior in such systems [43] as well as disorder-induced transitions from flocking to non-flocking states [44], and there are now experimental realizations of flocking systems with quenched disorder [45] that could be used to explore this question.…”

How many dissenters does it take to disorder a flock?

“…Previous work with static obstacles has found that tuning particle properties such as their repulsion [35] or their noise [10] can have a non-monotonic effect on their order and that, therefore, there are optimal values that maximize flocking in a disordered environment. These results, are, however, not directly applicable to the case with moving dissenters.…”

Dewetting and spreading transitions for active matter on random pinning substrates

“…The dynamics of many physically relevant active matter systems, such as particles moving over rough substrates, are better described in terms of an effective pinning landscape instead of in terms of obstacle avoidance. Studies of modified Vicsek models in the presence of obstacles showed that swarming was optimized at a particular noise value 24 , while in other studies, increasing the disorder strength caused a phase transition from a swarming to a non-swarming state 26 . In studies of self-propelled disks interacting with obstacle arrays, the mobility of the disks was a non-monotonic function of the running length, since disks with long running times spend more time trapped behind obstacles 23 .…”