arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1402.6466math.CO
收藏

随机图的二部分解

Bipartite decomposition of random graphs

Noga Alon

摘要:

对于图$G=(V,E)$,用$τ(G)$表示$G$的两两边不交的完全二部子图的最小数目,使得$G$的每条边恰好属于其中之一.很容易看出,对于每个图$G$,$τ(G) \leq n -α(G)$,其中$α(G)$是$G$的独立集合的最大大小。在80年代,Erdibs证明了几乎对每一个图$G$等式成立,即,即对于随机图$G(n,0.5)$,$τ(G)=n-α(G)$具有高概率,即具有趋于$1$的概率如同$n$趋于无穷大。在这里,我们表明,这一猜想是(略)假,证明大多数值的$n$趋于无穷大和$G=G(n,0.5)$,$τ(G) \leq n-α(G)-1$与高概率,并为一些序列的值的$n$趋于无穷大$τ(G) \leq n-α(G)-2$的概率有界远离$0$。本文还研究了具有$p < 0.5$的随机图$G=G(n,p)$的$τ(G)$的典型值,证明了存在一个绝对正的常数$c$,使得对所有的$p \leq c$和$G=G(n,p)$,$τ(G)=n-Θ(α(G))$以高概率存在.

英文摘要:

For a graph $G=(V,E)$, let $τ(G)$ denote the minimum number of pairwise edge disjoint complete bipartite subgraphs of $G$ so that each edge of $G$ belongs to exactly one of them. It is easy to see that for every graph $G$, $τ(G) \leq n -α(G)$, where $α(G)$ is the maximum size of an independent set of $G$. Erdős conjectured in the 80s that for almost every graph $G$ equality holds, i.e., that for the random graph $G(n,0.5)$, $τ(G)=n-α(G)$ with high probability, that is, with probability that tends to $1$ as $n$ tends to infinity. Here we show that this conjecture is (slightly) false, proving that for most values of $n$ tending to infinity and for $G=G(n,0.5)$, $τ(G) \leq n-α(G)-1$ with high probability, and that for some sequences of values of $n$ tending to infinity $τ(G) \leq n-α(G)-2$ with probability bounded away from $0$. We also study the typical value of $τ(G)$ for random graphs $G=G(n,p)$ with $p < 0.5$ and show that there is an absolute positive constant $c$ so that for all $p \leq c$ and for $G=G(n,p)$, $τ(G)=n-Θ(α(G))$ with high probability.

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。

↑