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arXiv 1607.01620cond-mat.stat-mech
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广义分形梳上的Lévy过程

Lévy processes on a generalized fractal comb

Trifce Sandev, Alexander Iomin, Vicenç Méndez

摘要:

梳状结构是二维结构中最简单的范例之一,它的反常扩散可以在马尔可夫过程的框架下实现。然而,结构的内在性质可以破坏这种马尔可夫传输。这些效应可以通过记忆和空间内核来描述。特别是,手指的分形结构,这是由实空间和傅立叶空间中的空间核控制,导致Lévy过程(Lévy航班)和超扩散。分数阶扩散的这种推广由Riesz空间分数阶导数描述。在这个广义分形梳模型的框架下,考虑了Lévy过程,得到了各种记忆核的概率分布函数的Fox $H$ -函数的精确解,并通过计算分数阶矩研究了超扩散扩散的速率.对于一种特殊形式的记忆内核,我们还观察到长休息和长跳跃之间的竞争。最后,我们考虑了由Weierstrass函数控制的手指的分数结构,这导致了傅立叶空间中的幂律核。这是一个特殊的情况下,当第二个时刻存在的超扩散之间的竞争长休息和跳远。

英文摘要:

Comb geometry, constituted of a backbone and fingers, is one of the most simple paradigm of a two dimensional structure, where anomalous diffusion can be realized in the framework of Markov processes. However, the intrinsic properties of the structure can destroy this Markovian transport. These effects can be described by the memory and spatial kernels. In particular, the fractal structure of the fingers, which is controlled by the spatial kernel in both the real and the Fourier spaces, leads to the Lévy processes (Lévy flights) and superdiffusion. This generalization of the fractional diffusion is described by the Riesz space fractional derivative. In the framework of this generalized fractal comb model, Lévy processes are considered, and exact solutions for the probability distribution functions are obtained in terms of the Fox $H$-function for a variety of the memory kernels, and the rate of the superdiffusive spreading is studied by calculating the fractional moments. For a special form of the memory kernels, we also observed a competition between long rests and long jumps. Finally, we considered the fractional structure of the fingers controlled by a Weierstrass function, which leads to the power-law kernel in the Fourier space. It is a special case, when the second moment exists for superdiffusion in this competition between long rests and long jumps.

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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