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arXiv 1602.09052math.COcs.DM
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关于排除固定子式图的广义着色数

On the Generalised Colouring Numbers of Graphs that Exclude a Fixed Minor

Jan van den Heuvel, Patrice Ossona de Mendez, Daniel Quiroz, Roman Rabinovich, Sebastian Siebertz

AI总结:

本文研究排除固定子式图的广义着色数上界,将原有指数界大幅改进为线性界和多项式界,并针对有界亏格图给出更精确的界。

摘要:

广义着色数 $\mathrm{col}_r(G)$ 和 $\mathrm{wcol}_r(G)$ 由 Kierstead 和 Yang 引入,作为通常着色数的推广,此后在理论和算法应用中具有重要意义。在本文中,我们大幅改进了排除固定子式的图的广义着色数的已知上界,从 Grohe 等人的指数界改进为 $r$-着色数 $\mathrm{col}_r$ 的线性界和弱 $r$-着色数 $\mathrm{wcol}_r$ 的多项式界。特别地,我们证明:如果 $G$ 排除 $K_t$ 作为子式,其中 $t\ge4$ 为某个固定值,则 $\mathrm{col}_r(G)\le\binom{t-1}{2}\\,(2r+1)$ 且 $\mathrm{wcol}_r(G)\le\binom{r+t-2}{t-2}\cdot(t-3)(2r+1)\in\mathcal{O}(r^{\\,t-1})$。对于有界亏格 $g$ 的图 $G$,我们将界改进为 $\mathrm{col}_r(G)\le(2g+3)(2r+1)$(当 $g=0$,即 $G$ 为平面图时,甚至可得 $\mathrm{col}_r(G)\le5r+1$)以及 $\mathrm{wcol}_r(G)\le\Bigl(2g+\binom{r+2}{2}\Bigr)\\,(2r+1)$。

英文摘要:

The generalised colouring numbers $\mathrm{col}_r(G)$ and $\mathrm{wcol}_r(G)$ were introduced by Kierstead and Yang as a generalisation of the usual colouring number, and have since then found important theoretical and algorithmic applications. In this paper, we dramatically improve upon the known upper bounds for generalised colouring numbers for graphs excluding a fixed minor, from the exponential bounds of Grohe et al. to a linear bound for the $r$-colouring number $\mathrm{col}_r$ and a polynomial bound for the weak $r$-colouring number $\mathrm{wcol}_r$. In particular, we show that if $G$ excludes $K_t$ as a minor, for some fixed $t\ge4$, then $\mathrm{col}_r(G)\le\binom{t-1}{2}\,(2r+1)$ and $\mathrm{wcol}_r(G)\le\binom{r+t-2}{t-2}\cdot(t-3)(2r+1)\in\mathcal{O}(r^{\,t-1})$. In the case of graphs $G$ of bounded genus $g$, we improve the bounds to $\mathrm{col}_r(G)\le(2g+3)(2r+1)$ (and even $\mathrm{col}_r(G)\le5r+1$ if $g=0$, i.e. if $G$ is planar) and $\mathrm{wcol}_r(G)\le\Bigl(2g+\binom{r+2}{2}\Bigr)\,(2r+1)$.

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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