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arXiv math/9312214math.CO
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三明治定理

The sandwich theorem

Donald E. Knuth

摘要:

本报告包含有关函数$\vartheta(G)$的简要说明,该函数通常称为图的Lovász数~ $G$。定义$\vartheta(G)$的方法有很多种,令人惊讶的各种不同特征本身就表明$\vartheta(G)$应该是有趣的。但是$\vartheta(G)$最有趣的性质可能是它可以被有效地计算的事实,尽管它位于其他经典图数之间,这些经典图数的计算是NP难的。我~曾试图使这些说明自成一体,使他们可能作为一个基本的介绍不断增长的文学洛瓦斯的迷人功能。

英文摘要:

This report contains expository notes about a function $\vartheta(G)$ that is popularly known as the Lovász number of a graph~$G$. There are many ways to define $\vartheta(G)$, and the surprising variety of different characterizations indicates in itself that $\vartheta(G)$ should be interesting. But the most interesting property of $\vartheta(G)$ is probably the fact that it can be computed efficiently, although it lies ``sandwiched'' between other classic graph numbers whose computation is NP-hard. I~have tried to make these notes self-contained so that they might serve as an elementary introduction to the growing literature on Lovász's fascinating function.

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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