论文标题
有效的Langevin方程式在活动浴中的极性示踪剂
Effective Langevin equations for a polar tracer in an active bath
论文作者
论文摘要
我们研究具有凹面表面的极性示踪剂，并浸入活性颗粒的二维悬浮液中。使用布朗动力学模拟，我们测量了活性颗粒在示踪剂上施加的力和扭矩的分布和自动相关函数。示踪剂沿其极轴经历有限的平均力，而所有相关函数均显示了指数衰减。使用这些见解，我们为示踪位置和方向构建了完整的粗粒度倾斜度描述，其中活性粒子被集中在有效的自我刺激力和指数相关的噪声中。随之而来的介质动力学可以用五个无量纲参数来描述。我们对平方位移进行了详尽的参数研究，该研究说明了不同参数如何影响示踪剂动力学，该动力学从弹道到扩散运动。我们还证明，示踪剂位移的分布从早期阶段的非高斯形状演变为长时间的高斯行为。
We study a polar tracer, having a concave surface, immersed in a two-dimensional suspension of active particles. Using Brownian dynamics simulations, we measure the distributions and auto-correlation functions of forces and torque exerted by active particles on the tracer. The tracer experiences a finite average force along its polar axis, while all the correlation functions show exponential decay in time. Using these insights we construct the full coarse-grained Langevin description for tracer position and orientation, where the active particles are subsumed into an effective self-propulsion force and exponentially correlated noise. The ensuing mesoscopic dynamics can be described in terms of five dimensionless parameters. We perform a thorough parameter study of the mean squared displacement, which illustrates how the different parameters influence the tracer dynamics, which crosses over from a ballistic to diffusive motion. We also demonstrate that the distribution of tracer displacements evolves from a non-Gaussian shape at early stages to a Gaussian behavior for sufficiently long times.
