arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1906.04249cond-mat.stat-mech
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无序系统中的输运:单大跳跃方法

Transport in disordered systems: the single big jump approach

Wanli Wang, Alessandro Vezzani, Raffaella Burioni, Eli Barkai

摘要:

在越来越多的强无序和稠密系统中,被外力场牵引的粒子的动力学表现出超扩散。在玻璃形成系统、过冷玻璃和污染物在多孔介质中扩散的背景下,建议用有偏连续时间随机游走来模拟这种行为。在这里,我们分析了远远落后于平均值的粒子羽流,与单大跳跃原则。揭示了异常的机制,我们展示了如何一个单一的捕获时间,最大的一个,是负责在系统中的罕见的波动。这些非典型的波动仍然控制着均方位移的行为,这是许多实验装置中动力学的最基本的量化器。我们展示了如何初始条件,描述无论是定态或非平衡的情况下,坚持永远在这个意义上说,罕见的波动是敏感的初始准备。为了描述最大捕获时间的波动,我们从极值统计中修改了Fréchet定律,考虑到大的波动与独立同分布随机变量所观察到的波动非常不同。

英文摘要:

In a growing number of strongly disordered and dense systems, the dynamics of a particle pulled by an external force field exhibits super-diffusion. In the context of glass forming systems, super cooled glasses and contamination spreading in porous medium it was suggested to model this behavior with a biased continuous time random walk. Here we analyze the plume of particles far lagging behind the mean, with the single big jump principle. Revealing the mechanism of the anomaly, we show how a single trapping time, the largest one, is responsible for the rare fluctuations in the system. These non typical fluctuations still control the behavior of the mean square displacement, which is the most basic quantifier of the dynamics in many experimental setups. We show how the initial conditions, describing either stationary state or non-equilibrium case, persist for ever in the sense that the rare fluctuations are sensitive to the initial preparation. To describe the fluctuations of the largest trapping time, we modify Fréchet's law from extreme value statistics, taking into consideration the fact that the large fluctuations are very different from those observed for independent and identically distributed random variables.

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