论文标题
与分数操作员的梳子模型中的淬火和退火障碍机制
Quenched and Annealed Disorder Mechanisms in Comb-Models with Fractional Operators
论文作者
论文摘要
关于异常扩散的最新实验发现要求将退火(时间)和淬火(空间或静态)疾病机制结合在一起。梳子模型是对渗滤簇扩散的简化描述,其中梳状结构模仿了淬火障碍机制,并产生了宽大的策略。在这里,我们将梳子模型扩展到同时考虑淬火和退火的疾病机制。为此,我们用不同的分数时间衍生算子和常规分形结构代替了梳子扩散方程中通常的衍生物。因此,我们的混合梳子模式代表了一个扩散,其中不同的梳状结构描述了不同的淬火障碍机制,而分数操作员则说明了各种退火疾病机制。我们找到了用于定义分数运算符的不同内存内核方面的扩散传播器和均方根位移的精确解。除其他发现外,我们还表明,这些模型描述了从细节到布朗或受到约束扩散的交叉,在经验结果中出现的情况。这些结果揭示了几何限制与记忆效应对建模异常扩散之间相互作用的关键作用。
Recent experimental findings on anomalous diffusion have demanded novel models that combine annealed (temporal) and quenched (spatial or static) disorder mechanisms. The comb-model is a simplified description of diffusion on percolation clusters, where the comb-like structure mimics quenched disorder mechanisms and yields a subdiffusive regime. Here we extend the comb-model to simultaneously account for quenched and annealed disorder mechanisms. To do so, we replace usual derivatives in the comb diffusion equation by different fractional time-derivative operators and the conventional comb-like structure by a generalized fractal structure. Our hybrid comb-models thus represent a diffusion where different comb-like structures describe different quenched disorder mechanisms, and the fractional operators account for various annealed disorders mechanisms. We find exact solutions for the diffusion propagator and mean square displacement in terms of different memory kernels used for defining the fractional operators. Among other findings, we show that these models describe crossovers from subdiffusion to Brownian or confined diffusions, situations emerging in empirical results. These results reveal the critical role of interactions between geometrical restrictions and memory effects on modeling anomalous diffusion.