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arXiv 1503.00558cond-mat.stat-mech
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淬火非均匀介质中布朗搜索的优化和普适性

Optimization and universality of Brownian search in quenched heterogeneous media

Aljaz Godec, Ralf Metzler

摘要:

各种运输控制过程的动力学可以归结为确定第一次到达给定位置所需的平均时间的问题,即所谓的平均首次通过时间(MFPT)问题。通过减少空间的过采样,已知组合各种类型的运动的偶尔的大跳跃或间歇模式的发生相对于MFPT优于标准的随机游走。在这里,我们表明,一个规则的,但空间异构的随机游走可以显着和普遍提高搜索在任何空间维度。在一个通用的极小模型中,我们考虑了一个球对称系统,该系统包括两个具有分段常数扩散率的同心区域。在守恒平均动力学约束下,即空间平均扩散率保持不变的情况下,分析了MFPT。我们的分析计算和广泛的数值模拟表明,存在一个{ \em最佳异质性}最小化的MFPT的目标。我们证明了随机行走的MFPT是完全由我们所称的直接轨迹向目标,并揭示了显着的普遍性的空间异构搜索目标的大小和系统维度。与在低空间维度中最有利可图的间歇性策略相反,空间非均匀搜索在更高维度中表现最好。讨论我们的研究结果以及最近的实验单粒子跟踪活细胞,我们认为,观察到的空间异质性可能是有益的细胞信号传导过程。

英文摘要:

The kinetics of a variety of transport-controlled processes can be reduced to the problem of determining the mean time needed to arrive at a given location for the first time, the so called mean first passage time (MFPT) problem. The occurrence of occasional large jumps or intermittent patterns combining various types of motion are known to outperform the standard random walk with respect to the MFPT, by reducing oversampling of space. Here we show that a regular but spatially heterogeneous random walk can significantly and universally enhance the search in any spatial dimension. In a generic minimal model we consider a spherically symmetric system comprising two concentric regions with piece-wise constant diffusivity. The MFPT is analyzed under the constraint of conserved average dynamics, that is, the spatially averaged diffusivity is kept constant. Our analytical calculations and extensive numerical simulations demonstrate the existence of an {\em optimal heterogeneity} minimizing the MFPT to the target. We prove that the MFPT for a random walk is completely dominated by what we term direct trajectories towards the target and reveal a remarkable universality of the spatially heterogeneous search with respect to target size and system dimensionality. In contrast to intermittent strategies, which are most profitable in low spatial dimensions, the spatially inhomogeneous search performs best in higher dimensions. Discussing our results alongside recent experiments on single particle tracking in living cells we argue that the observed spatial heterogeneity may be beneficial for cellular signaling processes.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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