arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1601.05058math.CO
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极性图中的独立集

Independent sets in polarity graphs

Michael Tait, Craig Timmons

摘要:

给定一个射影平面$Σ$和$Σ$的一个极性$θ$,对应的极性图是其顶点是$Σ$的点的图,并且如果$p_1$与$Σ$中的$p_2^{ θ}$相关联,则两个不同的点$p_1$和$p_2$相邻。极性图的一个著名例子是Erdens-Rényi正交极性图$ER_q$,它经常出现在各种极值问题中。特征值方法提供了一个上界的独立数的任何极性图。Mubayi和Williford指出,在$ER_q$的情况下,特征值方法给出了数量级的正确上限。我们证明,这也是真实的极性图的其他家庭。这包括极性图族,其极性既不是正交的也不是酉的。我们猜想$q$阶射影平面的任何极图都有一个大小为$Ω(q^{3/2})$的独立集。并得到了一些相关结果。

英文摘要:

Given a projective plane $Σ$ and a polarity $θ$ of $Σ$, the corresponding polarity graph is the graph whose vertices are the points of $Σ$, and two distinct points $p_1$ and $p_2$ are adjacent if $p_1$ is incident to $p_2^{ θ}$ in $Σ$. A well-known example of a polarity graph is the Erdős-Rényi orthogonal polarity graph $ER_q$, which appears frequently in a variety of extremal problems. Eigenvalue methods provide an upper bound on the independence number of any polarity graph. Mubayi and Williford showed that in the case of $ER_q$, the eigenvalue method gives the correct upper bound in order of magnitude. We prove that this is also true for other families of polarity graphs. This includes a family of polarity graphs for which the polarity is neither orthogonal nor unitary. We conjecture that any polarity graph of a projective plane of order $q$ has an independent set of size $Ω(q^{3/2})$. Some related results are also obtained.

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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