Hiraoka Takayuki, Shimada Takashi, Ito Nobuyasu
Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan.
RIKEN Advanced Institute for Computational Science, Kobe 650-0047, Japan.
Phys Rev E. 2016 Dec;94(6-1):062612. doi: 10.1103/PhysRevE.94.062612. Epub 2016 Dec 29.
We study the collective dynamics of repulsive self-propelled particles. The particles are governed by coupled equations of motion that include polar self-propulsion, damping of velocity and of polarity, repulsive particle-particle interaction, and deterministic dynamics. Particle dynamics simulations show that the collective coherent motion with large density fluctuations spontaneously emerges from a disordered, isotropic state. In the parameter region where the rotational damping of polarity is strong, the system undergoes an abrupt shift to the absorbing ordered state after a waiting period in the metastable disordered state. In order to obtain a simple understanding of the mechanism underlying the collective behavior, we analyze the binary particle scattering process. We show that this approach correctly predicts the order-disorder transition at a dilute limit. The same approach is expanded for finite densities, although it disagrees with the result from many-particle simulations due to many-body correlations and density fluctuations.
我们研究了相互排斥的自驱动粒子的集体动力学。这些粒子由耦合运动方程控制，该方程包括极性自推进、速度和极性的阻尼、粒子间的排斥相互作用以及确定性动力学。粒子动力学模拟表明，具有大密度涨落的集体相干运动自发地从无序、各向同性状态出现。在极性旋转阻尼较强的参数区域，系统在亚稳态无序状态经过一段等待期后会突然转变为吸收性有序状态。为了简单理解集体行为背后的机制，我们分析了二元粒子散射过程。我们表明，这种方法在稀薄极限下正确地预测了有序-无序转变。尽管由于多体关联和密度涨落，该方法与多粒子模拟结果不一致，但它被扩展到了有限密度情况。
