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arXiv 1608.05032math.PRmath.COphysics.geo-ph
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随机自相似树和一个层次分支过程

Random self-similar trees and a hierarchical branching process

Yevgeniy Kovchegov, Ilya Zaliapin

摘要:

本文研究随机二叉有根树的自相似性。在高尔顿-沃森树的一个很好理解的例子中,如果树空间上的分布对于修剪树叶的操作是不变的,那么它被称为自相似的。这只发生在临界的高尔顿-沃森树(一个常数过程的后代),它也表现出其他特殊的对称性。我们扩展的修剪不变设置任意的二叉树的边缘长度。在这种一般情况下,自相似过程的类别变得更加丰富,并涵盖了各种实际重要的情况。主要的结果是建设的层次分支过程,满足各种自相似性的定义(包括平均自相似性和自相似的边长)取决于过程参数。取平均随机动力学的极限,随着轨迹数的增加,我们得到一个确定性的微分方程系统,描述的过程演变。这个系统是用来建立一个相变,分离衰落和爆炸行为的平均过程的后代。我们描述了一类发生在相变边界的临界德永过程。他们享有多个额外的对称性,包括著名的临界二元Galton-Watson树与独立的指数边长度作为一个特殊情况。最后,我们讨论了树和连续函数之间的对偶性,并引入了一类极值不变过程,构造为自相似分层分支过程的Harris路径,其局部极小值具有与原始过程相同的(线性标度)分布。

英文摘要:

We study self-similarity in random binary rooted trees. In a well-understood case of Galton-Watson trees, a distribution on a space of trees is said to be self-similar if it is invariant with respect to the operation of pruning, which cuts the tree leaves. This only happens for the critical Galton-Watson tree (a constant process progeny), which also exhibits other special symmetries. We extend the prune-invariance setup to arbitrary binary trees with edge lengths. In this general case the class of self-similar processes becomes much richer and covers a variety of practically important situations. The main result is construction of the hierarchical branching processes that satisfy various self-similarity definitions (including mean self-similarity and self-similarity in edge-lengths) depending on the process parameters. Taking the limit of averaged stochastic dynamics, as the number of trajectories increases, we obtain a deterministic system of differential equations that describes the process evolution. This system is used to establish a phase transition that separates fading and explosive behavior of the average process progeny. We describe a class of critical Tokunaga processes that happen at the phase transition boundary. They enjoy multiple additional symmetries and include the celebrated critical binary Galton-Watson tree with independent exponential edge length as a special case. Finally, we discuss a duality between trees and continuous functions, and introduce a class of extreme-invariant processes, constructed as the Harris paths of a self-similar hierarchical branching process, whose local minima has the same (linearly scaled) distribution as the original process.

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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