Friction is central to the motion of active (self-propelled) objects such as bacteria, animals, and robots. While in a viscous fluid friction is described by Stokes’s law, objects in contact with other solid bodies are often governed by more complex empirical friction laws. Here, we study active particles subject to Coulomb friction using a combination of active granular experiments and simulations, supported by theoretical predictions. The interplay of friction and activity forces induces a rich behavior resulting in three distinct dynamical regimes. While for low activity Brownian motion is recovered, for large activity we observe a dynamical stop and go regime that continuously switches from diffusion and accelerated motion. For greater activity, we observe a supermobile dynamical regime characterized by a fully accelerated motion which is described by an anomalous scaling of the diffusion coefficient with the activity. These findings cannot be observed with Stokes viscous forces typical of active swimmers but are central in dry active objects.

中文翻译：

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具有库仑摩擦的惯性活性物质


摩擦力是细菌、动物和机器人等活动（自走式）物体运动的核心。在粘性流体中，摩擦由斯托克斯定律描述，而与其他固体接触的物体通常由更复杂的经验摩擦定律控制。在这里，我们结合使用活性颗粒实验和模拟来研究受库仑摩擦影响的活性颗粒，并得到理论预测的支持。摩擦力和活动力的相互作用引发了丰富的行为，从而产生了三种不同的动态状态。对于低活动，布朗运动被恢复，而对于大活动，我们观察到一个动态的停止和开始状态，它不断从扩散和加速运动之间切换。对于更大的活动，我们观察到一种超级移动的动力学状态，其特征是完全加速的运动，其描述是扩散系数随活动而异常缩放。这些发现不能用活跃游泳者典型的斯托克斯粘性力观察到，但在干燥的活跃物体中是核心。