Department of Physics and Astronomy, and Quantitative Biology Institute, Ohio University, Athens, Ohio 45701, USA.
Dipartimento di Fisica, Università di Camerino, I-62032 Camerino, Italy.
Phys Rev E. 2016 Jan;93(1):012606. doi: 10.1103/PhysRevE.93.012606. Epub 2016 Jan 13.
A sled is a stylized mechanical model of a system which is constrained to move in space in a specific orientation, i.e., in the direction of the runners of the sled or a blade. The negation of motion transverse to the runners renders the sled a nonholonomic mechanical system. In this paper we report on the unexpected and fascinating richness of the dynamics of such a sled if it is subject to random forces. Specifically we show that the ensuing random dynamics is characterized by relatively smooth sections of motion interspersed by episodes of persistent tumbling (change of orientation) and sharp reversals resembling the random walks of bacterial cells. In the presence of self-propulsion, the diffusivity of the sled can be enhanced and suppressed depending on the directionality and strength of the propulsive force.
雪橇是一个受约束的系统的简化机械模型，该系统只能在特定的方向上（即沿着雪橇或叶片的滑道）在空间中移动。运动方向与滑道垂直的运动被否定，使得雪橇成为一个非完整力学系统。本文报道了，如果雪橇受到随机力的作用，那么它的动力学会出人意料地变得非常丰富。具体来说，我们发现这种随机运动的特征是相对平滑的运动段，其间穿插着持续翻滚（方向改变）和急剧反转的片段，类似于细菌细胞的随机游动。在存在自推进的情况下，雪橇的扩散性可以根据推进力的方向和强度增强或抑制。
