从反常扩散到正常扩散的交叉：截断幂律噪声相关及其在脂双层动力学中的应用
Crossover from anomalous to normal diffusion: truncated power-law noise correlations and applications to dynamics in lipid bilayers
摘要：
在许多复杂系统中出现的扩散动力学表现出从反常扩散到正常扩散的特征交叉行为，否则由两个独立的幂律拟合。亚扩散-扩散交叉的一个突出例子是粘弹性系统，如脂质双层膜，而超扩散-扩散交叉发生在主动移动生物细胞的系统中。在这里，我们考虑由所谓的回火分数高斯噪声驱动的随机粒子的一般动力学，该噪声具有高斯振幅和幂律相关性，在某些介观时间尺度上被切断。具体来说，我们认为这样的噪声与内置的指数或幂律回火，驱动过阻尼朗之万方程（分数布朗运动）和分数朗之万方程运动。我们推导出显式的均方位移和关联函数，包括不同形状的交叉行为取决于混凝土回火，并讨论回火的物理意义。在幂律回火的情况下，我们也发现了一个交叉行为，从更快到更慢的超扩散和更慢到更快的次扩散。作为我们的模型的一个直接应用，我们证明了所获得的动力学定量描述的亚扩散扩散和亚扩散-亚扩散交叉的脂质双层系统。我们还表明，回火分数布朗运动最近提出的Sabzikar和Meerschaert模型导致物理上非常不同的行为与一个看似矛盾的弹道长时间标度。
英文摘要：
The emerging diffusive dynamics in many complex systems shows a characteristic crossover behaviour from anomalous to normal diffusion which is otherwise fitted by two independent power-laws. A prominent example for a subdiffusive-diffusive crossover are viscoelastic systems such as lipid bilayer membranes, while superdiffusive-diffusive crossovers occur in systems of actively moving biological cells. We here consider the general dynamics of a stochastic particle driven by so-called tempered fractional Gaussian noise, that is noise with Gaussian amplitude and power-law correlations, which are cut off at some mesoscopic time scale. Concretely we consider such noise with built-in exponential or power-law tempering, driving an overdamped Langevin equation (fractional Brownian motion) and fractional Langevin equation motion. We derive explicit expressions for the mean squared displacement and correlation functions, including different shapes of the crossover behaviour depending on the concrete tempering, and discuss the physical meaning of the tempering. In the case of power-law tempering we also find a crossover behaviour from faster to slower superdiffusion and slower to faster subdiffusion. As a direct application of our model we demonstrate that the obtained dynamics quantitatively described the subdiffusion-diffusion and subdiffusion-subdiffusion crossover in lipid bilayer systems. We also show that a model of tempered fractional Brownian motion recently proposed by Sabzikar and Meerschaert leads to physically very different behaviour with a seemingly paradoxical ballistic long time scaling.
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