Motile dissenters disrupt the flocking of active granular matter

How many dissenters does it take to disorder a flock?

We consider the effect of introducing a small number of non-aligning agents in a well-formed flock. To this end, we modify a minimal model of active Brownian particles with purely repulsive (excluded volume) forces to introduce an alignment interaction that will be experienced by all the particles except for a small minority of "dissenters". We find that even a very small fraction of dissenters disrupts the flocking state. Strikingly, these motile dissenters are much more effective than an equal number of static obstacles in breaking up the flock. For the studied system sizes we obtain clear e…

通过杆海进行编队

Flocking through a sea of rods

研究通过数值模拟揭示了运动杆在非极性介质中因反扩散不稳定性形成编队的现象，揭示了各向异性对编队结构的影响及最小平均场模型的解释。

Topology-driven ordering of flocking matter

When interacting motile units self-organize into flocks, they realize one of the most robust ordered state found in nature. However, after twenty five years of intense research, the very mechanism controlling the ordering dynamics of both living and artificial flocks has remained unsettled. Here, combining active-colloid experiments, numerical simulations and analytical work, we explain how flocking liquids heal their spontaneous flows initially plagued by collections of topological defects to achieve long-ranged polar order even in two dimensions. We demonstrate that the self-similar ordering…

Activity induced synchronization: From Mutual Flocking to Chiral Self-Sorting

Synchronization, the temporal coordination of coupled oscillators, allows fireflies to flash in unison, neurons to fire collectively and human crowds to fall in step on the London Millenium bridge. Here, we interpret active (or self-propelled) chiral microswimmers with a distribution of intrinsic frequencies as motile oscillators and show that they can synchronize over very large distances, even for local coupling in 2D. This opposes to canonical non-active oscillators on static or time-dependent networks, leading to synchronized domains only. A consequence of this activity-induced synchroniza…

Hamiltonian flocking模型中的重新进入现象

Reentrance in a Hamiltonian flocking model

该研究在哈密顿模型中揭示了均质相重新进入现象，通过自旋-速度耦合与动能摩擦的竞争机制解释了运动诱导相分离的行为。

Flocking at a distance in active granular matter

The self-organised motion of vast numbers of creatures in a single direction is a spectacular example of emergent order. We recreate this phenomenon using actuated non-living components. We report here that millimetre-sized tapered rods, rendered motile by contact with an underlying vibrated surface and interacting through a medium of spherical beads, undergo a phase transition to a state of spontaneous alignment of velocities and orientations above a threshold bead area fraction. Guided by a detailed simulation model, we construct an analytical theory of this flocking transition, with two ing…