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arXiv 0905.3146math.CO
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计数子结构I:颜色临界图

Counting substructures I: color critical graphs

Dhruv Mubayi

摘要:

设$F$是一个含有边的图,边的删除减少了它的色数。我们证明了严格的界限上的副本的数量$F$在一个图的规定数量的顶点和边。我们的结果扩展了Simonovits的结果,他们证明了$F$有一个拷贝,以及Rademacher,Erd \H os和Lovász-Simonovits的结果,当$F$是完全图时,他们证明了类似的计数结果。我们定理的一个最简单的例子是下面的新结果。存在一个绝对正常数$c$,使得如果$n$足够大且$1 \le q < cn$,则每个具有$n$偶数边和$n^2/4 +q$边的$n$顶点图至少包含五个循环的$q(n/2)(n/2-1)(n/2-2)$拷贝。类似的陈述适用于任何奇数循环,并且界限是最佳可能的。

英文摘要:

Let $F$ be a graph which contains an edge whose deletion reduces its chromatic number. We prove tight bounds on the number of copies of $F$ in a graph with a prescribed number of vertices and edges. Our results extend those of Simonovits, who proved that there is one copy of $F$, and of Rademacher, Erd\H os and Lovász-Simonovits, who proved similar counting results when $F$ is a complete graph. One of the simplest cases of our theorem is the following new result. There is an absolute positive constant $c$ such that if $n$ is sufficiently large and $1 \le q < cn$, then every $n$ vertex graph with $n$ even and $n^2/4 +q$ edges contains at least $q(n/2)(n/2-1)(n/2-2)$ copies of a five cycle. Similar statements hold for any odd cycle and the bounds are best possible.

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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