Institute of Physics, Humboldt University at Berlin, Berlin, Germany.
Phys Rev Lett. 2011 Jun 10;106(23):230601. doi: 10.1103/PhysRevLett.106.230601. Epub 2011 Jun 8.
We study the effect of different types of fluctuation on the motion of self-propelled particles in two spatial dimensions. We distinguish between passive and active fluctuations. Passive fluctuations (e.g., thermal fluctuations) are independent of the orientation of the particle. In contrast, active ones point parallel or perpendicular to the time dependent orientation of the particle. We derive analytical expressions for the speed and velocity probability density for a generic model of active Brownian particles, which yields an increased probability of low speeds in the presence of active fluctuations in comparison to the case of purely passive fluctuations. As a consequence, we predict sharply peaked Cartesian velocity probability densities at the origin. Finally, we show that such a behavior may also occur in non-Gaussian active fluctuations and discuss briefly correlations of the fluctuating stochastic forces.
我们研究了不同类型的涨落在二维空间中自主运动粒子运动的影响。我们区分了被动和主动涨落。被动涨落（例如热涨落）与粒子的方向无关。相比之下，主动涨落指向粒子随时间变化的方向平行或垂直。我们为一个通用的主动布朗粒子模型推导出了速度和速度概率密度的解析表达式，结果表明与纯粹的被动涨落相比，主动涨落会增加低速的概率。因此，我们预测在原点处笛卡尔速度概率密度会出现尖锐的峰值。最后，我们表明这种行为也可能发生在非高斯主动涨落中，并简要讨论了随机涨落力的相关性。
