arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2303.05723math.COcs.DM
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关于分裂图边着色与全着色的新结果

New Results on Edge-coloring and Total-coloring of Split Graphs

Fernanda Couto, Diego Amaro Ferraz, Sulamita Klein

AI总结:

本文针对 σ=2 的分裂图,利用按伸缩指数划分的结构,刻画 Class 2 与 Type 2 图,并为 Class 1、Type 1 图提供边着色和全着色的多项式算法。

摘要:

分裂图是顶点集可划分为一个团和一个独立集的图。若连通图 G 容许一棵特殊生成树,使任意两个相邻顶点在该树中的距离至多为 t,则称 G 是 t-可容许的。给定图 G,确定使 G 为 t-可容许的最小 t,即记为 σ(G) 的图的伸缩指数,是 t-可容许性问题的目标。分裂图是 3-可容许的,并可划分为三个子类:σ=1、2 或 3 的分裂图。本文在处理分裂图的着色问题时考虑了这种划分。Vizing 证明了任意图都可用 Δ 或 Δ+1 种颜色对其边着色,因此可分别归类为 Class 1 或 Class 2。当边和顶点同时着色,即对 G 进行全着色时,人们猜想任意图都可用 Δ+1 或 Δ+2 种颜色进行全着色,因此可归类为 Type 1 或 Type 2。这两个变体对分裂图而言仍未解决。本文利用上述分裂图的划分,研究 σ=2 的分裂图的边着色问题和全着色问题。对于该类图,我们刻画了 Class 2 和 Type 2 图,并给出了对任意 Class 1 或 Type 1 图进行着色的多项式时间算法。

英文摘要:

A split graph is a graph whose vertex set can be partitioned into a clique and an independent set. A connected graph $G$ is said to be $t$-admissible if admits a special spanning tree in which the distance between any two adjacent vertices is at most $t$. Given a graph $G$, determining the smallest $t$ for which $G$ is $t$-admissible, i.e. the stretch index of $G$ denoted by $σ(G)$, is the goal of the $t$-admissibility problem. Split graphs are $3$-admissible and can be partitioned into three subclasses: split graphs with $σ=1, 2 $ or $3$. In this work we consider such a partition while dealing with the problem of coloring a split graph. Vizing proved that any graph can have its edges colored with $Δ$ or $Δ+1$ colors, and thus can be classified as Class 1 or Class 2, respectively. When both, edges and vertices, are simultaneously colored, i.e., a total coloring of $G$, it is conjectured that any graph can be total colored with $Δ+1$ or $Δ+2$ colors, and thus can be classified as Type 1 or Type 2. These both variants are still open for split graphs. In this paper, using the partition of split graphs presented above, we consider the edge coloring problem and the total coloring problem for split graphs with $σ=2$. For this class, we characterize Class 2 and Type 2 graphs and we provide polynomial-time algorithms to color any Class 1 or Type 1 graph.

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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