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arXiv 0911.4499physics.soc-phcond-mat.dis-nn
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随机网络上具有阈值规则的级联动态模型

A Dynamic Model of Cascades on Random Networks with a Threshold Rule

Daniel E. Whitney

摘要:

随机网络上的级联通常通过假设它们映射到渗流过程来分析,然后使用生成函数公式求解。这种方法假设网络是无限的和弱连接的,但进一步近似的动态级联过程作为一个静态的渗流事件。在本文中,我们提出了一个动态马尔可夫模型制定,假设一个有限的网络与任意平均节点度。我们将其应用到级联遵循阈值规则的情况下,也就是说,一个节点将改变状态(“翻转”),只有当一小部分,超过给定的阈值,它的邻居已经改变了以前的状态。在每一步之后重新计算的对应的状态转移矩阵记录了在级联的演化中的j步之后k度的节点具有i个翻转邻居的概率。该理论模型再现了在模拟中观察到的一些行为,但尚未在文献中报道。这些包括在先前预测禁止级联的域中预测级联的能力,而无需假设网络是局部树状的,并且由于模型的动态性质,级联最初出现即将死亡但后来爆炸的“濒死”行为。在“无级联”区域中的级联需要初始翻转节点的足够大的种子,其大小与网络的大小成比例,否则级联将消失。我们的理论还预测了级联的众所周知的属性,例如,一个单一的节点种子可以启动一个全球级联在适当的制度,无论(有限)的网络大小。这里开发的理论和模拟进行比较的基础文件瓦茨使用生成函数理论。

英文摘要:

Cascades on random networks are typically analyzed by assuming they map onto percolation processes and then are solved using generating function formulations. This approach assumes that the network is infinite and weakly connected, yet furthermore approximates a dynamic cascading process as a static percolation event. In this paper we propose a dynamic Markov model formulation that assumes a finite network with arbitrary average nodal degree. We apply it to the case where cascades follow a threshold rule, that is, that a node will change state ("flip") only if a fraction, exceeding a given threshold, of its neighbors has changed state previously. The corresponding state transition matrix, recalculated after each step, records the probability that a node of degree k has i flipped neighbors after j steps in the cascade's evolution. This theoretical model reproduces a number of behaviors observed in simulations but not yet reported in the literature. These include the ability to predict cascades in a domain previously predicted to forbid cascades without assuming that the network is locally tree-like, and, due to the dynamic nature of the model, a "near death" behavior in which cascades initially appear about to die but later explode. Cascades in the "no cascades" region require a sufficiently large seed of initially flipped nodes whose size scales with the size of the network or else the cascade will die out. Our theory also predicts the well known properties of cascades, for instance that a single node seed can start a global cascade in the appropriate regime regardless of the (finite) size of the network. The theory and simulations developed here are compared with a foundational paper by Watts which used generating function theory.

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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