论文标题

布朗颗粒系统中的竞争:令人鼓舞的成就者

Competition in a system of Brownian particles: Encouraging achievers

论文作者

Krapivsky, P. L., Vilk, Ohad, Meerson, Baruch

论文摘要

我们在分析和数字上介绍和研究一个简单的代理间竞争模型,在该竞争中,实验室不足。我们认为$ n \ gg 1 $颗粒在线上执行独立的布朗运动。随机和随机选择两个颗粒,最接近原点的粒子重置为其。我们表明,在$ n \至\ infty $的极限中,可以通过非局部流体动力学理论来描述粗粒粒子密度场的动力学,该理论在对关键方案中流行病的空间范围的研究中遇到。流体动力学理论可以预测系统的放松朝向“群体群”的固定密度分布,该密度在较大的距离上表现出幂律衰减。这种放松的一个有趣特征是固定解决方案周围的非平稳性“光晕”,该解决方案继续以自相似的方式扩展。最终以有限的$ n $效果以订单$ \ sqrt {n} $的距离捕获,从而估算了群的平均半径。流体动力学理论并未捕获粒子最远的粒子的行为 - 目前的领导者。我们建议一个简单的方案,即领导者距离原始距离的典型波动,并表明平均距离继续无限期地增长为$ \ sqrt {t} $。最后,我们将代理竞赛从$ n = 2 $扩展到任意数字$ n $的竞争性布朗颗粒($ n \ ll n $)。我们的分析预测由蒙特卡洛模拟支持。

We introduce and study analytically and numerically a simple model of inter-agent competition, where underachievement is strongly discouraged. We consider $N\gg 1$ particles performing independent Brownian motions on the line. Two particles are selected at random and at random times, and the particle closest to the origin is reset to it. We show that, in the limit of $N\to \infty$, the dynamics of the coarse-grained particle density field can be described by a nonlocal hydrodynamic theory which was encountered in a study of the spatial extent of epidemics in a critical regime. The hydrodynamic theory predicts relaxation of the system toward a stationary density profile of the "swarm" of particles, which exhibits a power-law decay at large distances. An interesting feature of this relaxation is a non-stationary "halo" around the stationary solution, which continues to expand in a self-similar manner. The expansion is ultimately arrested by finite-$N$ effects at a distance of order $\sqrt{N}$ from the origin, which gives an estimate of the average radius of the swarm. The hydrodynamic theory does not capture the behavior of the particle farthest from the origin -- the current leader. We suggest a simple scenario for typical fluctuations of the leader's distance from the origin and show that the mean distance continues to grow indefinitely as $\sqrt{t}$. Finally, we extend the inter-agent competition from $n=2$ to an arbitrary number $n$ of competing Brownian particles ($n\ll N$). Our analytical predictions are supported by Monte-Carlo simulations.

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