arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2001.07850math.CO
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完全图的笛卡儿积的全$k$ -控制

Total $k$-domination in Cartesian product of complete graphs

Walter Carballosa, Justin Wisby

摘要:

设$G=(V,E)$是一个有限无向图. $V$中的顶点的集合$S$被称为全$k$ -支配的,如果$V$中的每个顶点至少与$S$中的$k$顶点相邻。全$k$ -控制数,$γ_{kt}(G)$,是$G$中全$k$ -控制集的最小基数.本文研究了两个完全图的笛卡儿积的$k$ -控制数,它是两个图的笛卡儿积的$k$ -控制数的一个下界.得到了两个完全图的笛卡儿积的$k$ -控制数的新的上下界.特别地,我们得到了阶至少为$n$的图$G,H$的$\displaystyle\liminf_{n\to\infty}\frac{γ_{kt}(G\Box H)}{n}\leq 2\,\left(\left\lceil\frac{k}{2}\right\rceil^{-1}+\left\lfloor\frac{k+4}{2}\right\rfloor^{-1}\right)^{-1}$.我们还证明了当且仅当$k$是偶数时,等式才成立。当$G,H$都同构于具有$n$顶点的完全图$K_n$时,等式成立。进一步,我们得到了两个任意阶的完全图的笛卡儿积的全$2$ -控制数的封闭公式.此外,我们还证明了对于$k=3$,上述不等式可改进为$\displaystyle\liminf_{n\to\infty} γ_{3t}(K_n\Box K_n)/n \leq 11/5$ .

英文摘要:

Let $G=(V,E)$ be a finite undirected graph. A set $S$ of vertices in $V$ is said to be total $k$-dominating if every vertex in $V$ is adjacent to at least $k$ vertices in $S$. The total $k$-domination number, $γ_{kt}(G)$, is the minimum cardinality of a total $k$-dominating set in $G$. In this work we study the total $k$-domination number of Cartesian product of two complete graphs which is a lower bound of the total $k$-domination number of Cartesian product of two graphs. We obtain new lower and upper bounds for the total $k$-domination number of Cartesian product of two complete graphs. Some asymptotic behaviors are obtained as a consequence of the bounds we found. In particular, we obtain that $\displaystyle\liminf_{n\to\infty}\frac{γ_{kt}(G\Box H)}{n}\leq 2\,\left(\left\lceil\frac{k}{2}\right\rceil^{-1}+\left\lfloor\frac{k+4}{2}\right\rfloor^{-1}\right)^{-1}$ for graphs $G,H$ with order at least $n$. We also prove that the equality is attained if and only if $k$ is even. The equality holds when $G,H$ are both isomorphic to the complete graph, $K_n$, with $n$ vertices. Furthermore, we obtain closed formulas for the total $2$-domination number of Cartesian product of two complete graphs of whatever order. Besides, we prove that, for $k=3$, the inequality above is improvable to $\displaystyle\liminf_{n\to\infty} γ_{3t}(K_n\Box K_n)/n \leq 11/5$.

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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