arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2210.04712math.CO
收藏

关于一个子图恰好包含k个副本的图及搜索论中的一个相关问题

On graphs that contain exactly k copies of a subgraph, and a related problem in search theory

Dániel Gerbner, Balázs Keszegh, Dániel Lenger, Dániel T. Nagy, Dömötör Pálvölgyi, Balázs Patkós, Máté Vizer, Gábor Wiener

摘要:

我们研究了$\mathrm{exa}_k(n,F)$,在一个$n$ -顶点图$G$中的最大边数,它恰好包含给定子图$F$的$k$副本。$k=0$是图兰数$\mathrm{ex}(n,F)$,它是极值图论中研究最多的参数之一。我们表明,对于任何$F$和$k$,$\mathrm{exa}_k(n,F)=(1+o(1))\mathrm{ex}(n,F))$,并确定$n$足够大的$\mathrm{exa}_k(n,K_3)$和$\mathrm{exa}_1(n,K_r)$的精确值。我们还探讨了与以下搜索论中的著名问题的联系。我们给出了一个图的顺序$n$,它由一个未知的副本$F$和一些孤立的顶点。我们可以询问成对的顶点作为查询,答案告诉我们这些顶点之间是否有边。我们的目标是使用尽可能少的查询来描述图。Aigner和Triesch在1990年指出,所需的查询数至少为$\binom{n}{2}-\mathrm{exa}_1(n,F)$。在其他结果中,我们表明,回答NO的查询的数量至少是$\binom{n}{2}-\mathrm{exa}_1(n,F)$。

英文摘要:

We study $\mathrm{exa}_k(n,F)$, the largest number of edges in an $n$-vertex graph $G$ that contains exactly $k$ copies of a given subgraph $F$. The case $k=0$ is the Turán number $\mathrm{ex}(n,F)$ that is among the most studied parameters in extremal graph theory. We show that for any $F$ and $k$, $\mathrm{exa}_k(n,F)=(1+o(1))\mathrm{ex}(n,F))$ and determine the exact values of $\mathrm{exa}_k(n,K_3)$ and $\mathrm{exa}_1(n,K_r)$ for $n$ large enough. We also explore a connection to the following well-known problem in search theory. We are given a graph of order $n$ that consists of an unknown copy of $F$ and some isolated vertices. We can ask pairs of vertices as queries, and the answer tells us whether there is an edge between those vertices. Our goal is to describe the graph using as few queries as possible. Aigner and Triesch in 1990 showed that the number of queries needed is at least $\binom{n}{2}-\mathrm{exa}_1(n,F)$. Among other results we show that the number of queries that were answered NO is at least $\binom{n}{2}-\mathrm{exa}_1(n,F)$.

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。

↑