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arXiv 0802.1338cs.DMcs.CCcs.DS
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关于(a:b)-可选性的一些结果

Some results on (a:b)-choosability

Shai Gutner, Michael Tarsi

摘要:

通过证明如果图$G$是$(a:b)$ -可选的,且$c/d > a/b$是可选的,则$G$不一定是$(c:d)$ -可选的,得到了Erdés,Rubin和Taylor问题的一个解.应用概率方法,给出了图的$k^{th}$选择数的一个上界.证明了具有最大出度$d$且无奇有向圈的有向图对每个$k \geq 1$都是$(k(d+1):k)$ -可选的.本文给出的其他结果与图的强选择数(强色数的推广)有关。我们的结论与复杂性分析的一些决策问题有关的图的可选性。

英文摘要:

A solution to a problem of Erdős, Rubin and Taylor is obtained by showing that if a graph $G$ is $(a:b)$-choosable, and $c/d > a/b$, then $G$ is not necessarily $(c:d)$-choosable. Applying probabilistic methods, an upper bound for the $k^{th}$ choice number of a graph is given. We also prove that a directed graph with maximum outdegree $d$ and no odd directed cycle is $(k(d+1):k)$-choosable for every $k \geq 1$. Other results presented in this article are related to the strong choice number of graphs (a generalization of the strong chromatic number). We conclude with complexity analysis of some decision problems related to graph choosability.

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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