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arXiv 1004.0583math.ATmath.CO
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与$r$ -图相关的Hom复形和盒复形的简单$S_r$ -同伦类型

Simple $S_r$-homotopy types of Hom complexes and box complexes associated to $r$-graphs

Thorranin Thansri

摘要:

对于一对图的$(H_1,H_2)$,Lovász引入了一个称为Hom复形$\text{Hom}(H_1,H_2)$的多面体复形,以估计图的色数的拓扑下界。该定义被推广到超图。用$K_r^r$表示以$r$为顶点的完全$r$ -图.给定一个$r$ -图$H$,我们将$\text{Hom}(K_r^r,H)$与Alon,Frankl和Lovász发明的盒复形$\mathsf{B}_{\text{edge}}(H)$进行比较。证明了$\text{Hom}(K_r^r,H)$和$\mathsf{B}_{\text{edge}}(H)$都具有对称群在$r$字母$S_r$上的右作用,它们具有相同的简单$S_r$ -同伦类型.

英文摘要:

For a pair $(H_1,H_2)$ of graphs, Lovász introduced a polytopal complex called the Hom complex $\text{Hom}(H_1,H_2)$, in order to estimate topological lower bounds for chromatic numbers of graphs. The definition is generalized to hypergraphs. Denoted by $K_r^r$ the complete $r$-graph on $r$ vertices. Given an $r$-graph $H$, we compare $\text{Hom}(K_r^r,H)$ with the box complex $\mathsf{B}_{\text{edge}}(H)$, invented by Alon, Frankl and Lovász. We verify that $\text{Hom}(K_r^r,H)$ and $\mathsf{B}_{\text{edge}}(H)$, both are equipped with right actions of the symmetric group on $r$ letters $S_r$, are of the same simple $S_r$-homotopy type.

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