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arXiv 2202.02570math.COcs.DM
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可平面图关于邻域的真无冲突唯一极大染色

Proper conflict-free and unique-maximum colorings of planar graphs with respect to neighborhoods

Igor Fabrici, Borut Lužar, Simona Rindošová, Roman Soták

摘要:

图{ \em相对于开}的{ \em无冲突着色}(相应地,{ \em closed}){ \em neighborhood}是顶点的着色,使得对于每个顶点,在其开域中存在恰好出现一次的颜色(相应地,关闭)社区。类似地,图{\em相对于开}的{\em唯一最大着色}(分别,{ \em closed}){ \em neighborhood}是顶点的着色,使得对于每个顶点,出现在其开放(相应地,封闭的)邻居只出现一次。关于这两个概念有大量的文献,其中着色不需要适当,即,允许邻顶点具有相同的颜色。本文主要研究可平面图的两种着色问题。我们建立了上界的颜色的数量在类的可平面图的所有考虑的着色,并提供建设的可平面图达到相对较高的值,相应的色数。作为主要结果,我们证明了每个平面图都有关于开邻域的最多10种颜色的唯一最大真染色,并给出了可平面图至少需要$6$颜色的例子.我们还建立了外平面图的紧上界。最后,我们提供了几个新的界限也考虑着色的不适当的设置。

英文摘要:

A {\em conflict-free coloring} of a graph {\em with respect to open} (resp., {\em closed}) {\em neighborhood} is a coloring of vertices such that for every vertex there is a color appearing exactly once in its open (resp., closed) neighborhood. Similarly, a {\em unique-maximum coloring} of a graph {\em with respect to open} (resp., {\em closed}) {\em neighborhood} is a coloring of vertices such that for every vertex the maximum color appearing in its open (resp., closed) neighborhood appears exactly once. There is a vast amount of literature on both notions where the colorings need not be proper, i.e., adjacent vertices are allowed to have the same color. In this paper, we initiate a study of both colorings in the proper settings with the focus given mainly to planar graphs. We establish upper bounds for the number of colors in the class of planar graphs for all considered colorings and provide constructions of planar graphs attaining relatively high values of the corresponding chromatic numbers. As a main result, we prove that every planar graph admits a proper unique-maximum coloring with respect to open neighborhood with at most 10 colors, and give examples of planar graphs needing at least $6$ colors for such a coloring. We also establish tight upper bounds for outerplanar graphs. Finally, we provide several new bounds also for the improper setting of considered colorings.

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