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arXiv 2104.04898math.CO
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平面三角剖分中哈密顿圈的个数

Number of Hamiltonian cycles in planar triangulations

Xiaonan Liu, Xingxing Yu

摘要:

惠特尼在1931年证明了4-连通平面三角剖分是哈密尔顿的。Hakimi、Schmeichel和Schlassen在1979年证明了,如果$G$是一个4连通的平面三角网,其顶点是$n$,那么$G$至少包含$2(n-2)(n-4)$哈密顿圈,当且仅当$G$是一个双轮时,$G$相等。另一方面,最近的结果Alahmadi,Aldred,和Aldassen国家,有指数许多哈密顿圈在5-连通平面三角形。本文研究了4-连通平面$n$ -顶点三角剖分$G$,它不具有太多的分离4-圈或最小度为5。证明了若$G$有$O(n/{\log}_2 n)$分隔4-圈则$G$有$Ω(n^2)$哈密顿圈,若$δ(G)\ge 5$有$G$有$2^{Ω(n^{1/4})}$哈密顿圈.这两个结果改进了以前的工作。此外,证明涉及一个“双轮”结构,提供了进一步的证据,上述猜想。

英文摘要:

Whitney proved in 1931 that 4-connected planar triangulations are Hamiltonian. Hakimi, Schmeichel, and Thomassen conjectured in 1979 that if $G$ is a 4-connected planar triangulation with $n$ vertices then $G$ contains at least $2(n-2)(n-4)$ Hamiltonian cycles, with equality if and only if $G$ is a double wheel. On the other hand, a recent result of Alahmadi, Aldred, and Thomassen states that there are exponentially many Hamiltonian cycles in 5-connected planar triangulations. In this paper, we consider 4-connected planar $n$-vertex triangulations $G$ that do not have too many separating 4-cycles or have minimum degree 5. We show that if $G$ has $O(n/{\log}_2 n)$ separating 4-cycles then $G$ has $Ω(n^2)$ Hamiltonian cycles, and if $δ(G)\ge 5$ then $G$ has $2^{Ω(n^{1/4})}$ Hamiltonian cycles. Both results improve previous work. Moreover, the proofs involve a "double wheel" structure, providing further evidence to the above conjecture.

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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