arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1002.1960math.CO
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从Coxeter图到Klein图

From the Coxeter graph to the Klein graph

Italo J. Dejter

摘要:

我们证明了56点Klein三次图$\G'$可以由28点Coxeter三次图$\G$通过充分“压缩”$\G$的24个7-圈的平方而得到,赋予$\G$作为$\mathcal C$ -超齐次有向图而得到的定向,其中,$\mathcal C$是由定向的7-环$\vec{C}_7$和2-弧$\vec{P}_3$形成的集合,所述$\vec{P}_3$将这些$\vec{C}_7$紧密地固定在$\G$中。在该过程中,可以看出$\G'$是一个${\mathcal C}'$ -超齐次(无向)图,其中${\mathcal C}'$是由7-圈$C_7$和1-路径$P_2$形成的集合,它们将这些$C_7$紧密地固定在$\G'$中。这产生$\G'$嵌入到3-torus $T_3$中,其形成Coxeter符号$(7,3)_8$的Klein映射。$T_3$中的$\G'$的对偶图是距离正则的Klein四次图,对应的对偶映射用Coxeter符号$(3,7)_8$表示.

英文摘要:

We show that the 56-vertex Klein cubic graph $\G'$ can be obtained from the 28-vertex Coxeter cubic graph $\G$ by 'zipping' adequately the squares of the 24 7-cycles of $\G$ endowed with an orientation obtained by considering $\G$ as a $\mathcal C$-ultrahomogeneous digraph, where $\mathcal C$ is the collection formed by both the oriented 7-cycles $\vec{C}_7$ and the 2-arcs $\vec{P}_3$ that tightly fasten those $\vec{C}_7$ in $\G$. In the process, it is seen that $\G'$ is a ${\mathcal C}'$-ultrahomogeneous (undirected) graph, where ${\mathcal C}'$ is the collection formed by both the 7-cycles $C_7$ and the 1-paths $P_2$ that tightly fasten those $C_7$ in $\G'$. This yields an embedding of $\G'$ into a 3-torus $T_3$ which forms the Klein map of Coxeter notation $(7,3)_8$. The dual graph of $\G'$ in $T_3$ is the distance-regular Klein quartic graph, with corresponding dual map of Coxeter notation $(3,7)_8$.

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