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arXiv 1602.05937math.CO
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中等密度图的收敛性

Convergence of graphs with intermediate density

Péter E. Frenkel

摘要:

我们提出了一个图收敛的概念,它介于有界度图的Benjamini-Schramm收敛和László Lovász及其合著者提出的稠密图收敛之间。我们证明了图的谱,以及一些重要的图参数,如着色数或匹配数,在收敛图序列中表现良好。特别注意的是大的本质围长的图序列,显式计算的着色数的渐近。我们还讨论了近似正则图中匹配的个数。我们引入试探性的极限对象,我们称之为graphonings,因为它们是graphons和graphings的共同推广。它们的特殊形式,称为豪斯多夫和欧几里德图符,涉及几何测度论。我们构建欧氏图,提供超立方体和有限的射影平面的限制,更一般地说,一类广泛的正则序列的大本质围长。对于任何大本质围长的收敛序列,我们构造较弱的极限对象:一致测度序列的次马尔可夫空间上的对合不变概率测度(这是唯一的),或者概率空间上的非循环可逆次马尔可夫核(非唯一的)。我们也提出了一些开放的问题。

英文摘要:

We propose a notion of graph convergence that interpolates between the Benjamini--Schramm convergence of bounded degree graphs and the dense graph convergence developed by László Lovász and his coauthors. We prove that spectra of graphs, and also some important graph parameters such as numbers of colorings or matchings, behave well in convergent graph sequences. Special attention is given to graph sequences of large essential girth, for which asymptotics of coloring numbers are explicitly calculated. We also treat numbers of matchings in approximately regular graphs. We introduce tentative limit objects that we call graphonings because they are common generalizations of graphons and graphings. Special forms of these, called Hausdorff and Euclidean graphonings, involve geometric measure theory. We construct Euclidean graphonings that provide limits of hypercubes and of finite projective planes, and, more generally, of a wide class of regular sequences of large essential girth. For any convergent sequence of large essential girth, we construct weaker limit objects: an involution invariant probability measure on the sub-Markov space of consistent measure sequences (this is unique), or an acyclic reversible sub-Markov kernel on a probability space (non-unique). We also pose some open problems.

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