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arXiv 1803.05085math.COcs.DM
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Kuratowski Minor的$\mathbb{Z}_2$属

The $\mathbb{Z}_2$-genus of Kuratowski minors

Radoslav Fulek, Jan Kynčl

摘要:

在曲面上画一个图是独立的,即使图中每对不相邻的边相交偶数次。图$G$的$\mathbb{Z}_2$ -亏格是最小$g$使得$G$在亏格$g$的可定向曲面上有独立偶图. Robertson和Seymour的一个未发表的结果暗示,对于每个$t$,每个足够大的亏格的图都包含一个投影$t\times t$网格或以下所谓的$t$ -Kuratowski图之一作为子图:$K_{3,t}$,或$K_5$或$K_{3,3}$的$t$副本共享最多两个公共顶点。我们证明了这些族中的图的$\mathbb{Z}_2$ -亏格在$t$中是无界的;事实上,等于它们的亏格。总之,这意味着图的亏格从上到下由其$\mathbb{Z}_2$ -亏格的函数来界定,解决了Schaefer和Štefankovič提出的问题,并给出了关于可定向曲面的Hanani-Tutte定理的近似版本。对于图的Euler亏格和Euler $\mathbb{Z}_2$ -亏格,我们也得到了类似的结果.

英文摘要:

A drawing of a graph on a surface is independently even if every pair of nonadjacent edges in the drawing crosses an even number of times. The $\mathbb{Z}_2$-genus of a graph $G$ is the minimum $g$ such that $G$ has an independently even drawing on the orientable surface of genus $g$. An unpublished result by Robertson and Seymour implies that for every $t$, every graph of sufficiently large genus contains as a minor a projective $t\times t$ grid or one of the following so-called $t$-Kuratowski graphs: $K_{3,t}$, or $t$ copies of $K_5$ or $K_{3,3}$ sharing at most two common vertices. We show that the $\mathbb{Z}_2$-genus of graphs in these families is unbounded in $t$; in fact, equal to their genus. Together, this implies that the genus of a graph is bounded from above by a function of its $\mathbb{Z}_2$-genus, solving a problem posed by Schaefer and Štefankovič, and giving an approximate version of the Hanani-Tutte theorem on orientable surfaces. We also obtain an analogous result for Euler genus and Euler $\mathbb{Z}_2$-genus of graphs.

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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