论文标题

分数fokker-Planck方程后异常次扩散的极端统计:次扩散比正常扩散快

Extreme statistics of anomalous subdiffusion following a fractional Fokker-Planck equation: Subdiffusion is faster than normal diffusion

论文作者

Lawley, Sean D

论文摘要

异常的细胞扩散表征了各种物理系统中的运输,并且在生物细胞内尤为普遍。在细胞生物学中,化学激活率的流行模型最近从单个搜索者的第一个通道时间(FPT)变为许多搜索者中最快的搜索者的fpt,以达到目标,这被称为极端统计或极端fpt。在本文中,我们调查了通过异常细节移动的搜索者的极端统计数据。我们通过涉及Riemann-Liouville分数衍生物的分数fokker-Planck方程来对尺寸进行尺寸。我们证明了一个明确的,非常通用的公式,对于极端fpts的每一刻,并近似它们的全部概率分布。虽然单个副搜索者的平均fpt是无限的,但在许多副搜索者中,最快的副搜索者通常具有有限的均值fpt。实际上,我们证明了违反直觉的结果,即极端扩散的极端FPT比正常扩散的极端FPT快。从数学上讲,我们采用随机表示,涉及标准ITO漂移扩散的随机变化,这是根据征费下属的第一个交叉时间的轨迹。我们分析的关键步骤是将Varadhan的公式从大偏差理论概述到次扩散的情况,该公式从某个地理距离方面产生了次扩散的短时分布。

Anomalous subdiffusion characterizes transport in diverse physical systems and is especially prevalent inside biological cells. In cell biology, the prevailing model for chemical activation rates has recently changed from the first passage time (FPT) of a single searcher to the FPT of the fastest searcher out of many searchers to reach a target, which is called an extreme statistic or extreme FPT. In this paper, we investigate extreme statistics of searchers which move by anomalous subdiffusion. We model subdiffusion by a fractional Fokker-Planck equation involving the Riemann-Liouville fractional derivative. We prove an explicit and very general formula for every moment of subdiffusive extreme FPTs and approximate their full probability distribution. While the mean FPT of a single subdiffusive searcher is infinite, the fastest subdiffusive searcher out of many subdiffusive searchers typically has a finite mean FPT. In fact, we prove the counterintuitive result that extreme FPTs of subdiffusion are faster than extreme FPTs of normal diffusion. Mathematically, we employ a stochastic representation involving a random time change of a standard Ito drift-diffusion according to the trajectory of the first crossing time inverse of a Levy subordinator. A key step in our analysis is generalizing Varadhan's formula from large deviation theory to the case of subdiffusion, which yields the short-time distribution of subdiffusion in terms of a certain geodesic distance.

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