Snarks, Hypohamiltonian Graphs and Non-Supereulerian Graphs

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• 作者：Zhi-Hong Chen
• 关键词：Hypohamiltonian graphs ; Snarks ; Supereulerian graphs ; Collapsible graphs
• 刊名：Graphs and Combinatorics
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：32
• 期：6
• 页码：2267-2273
• 全文大小：424 KB
• 刊物类别：Mathematics and Statistics
• 刊物主题：Mathematics
  Combinatorics
  Engineering Design
  
• 出版者：Springer Japan
• ISSN：1435-5914
• 卷排序：32

文摘

A graph G is hypohamiltonian if it is not Hamiltonian but for each \(v\in V(G)\), the graph \(G-v\) is Hamiltonian. A graph is supereulerian if it has a spanning Eulerian subgraph. A graph G is called collapsible if for every even subset \(R\subseteq V(G)\), there is a spanning connected subgraph H of G such that R is the set of vertices of odd degree in H. A graph is reduced if it has no nontrivial collapsible subgraphs. In this note, we first prove that all hypohamiltonian cubic graphs are reduced non-supereulerian graphs. Then we introduce an operation to construct graphs from hypohamiltonian cubic graphs such that the resulting graphs are 3-edge-connected non-supereulerian reduced graphs and cannot be contracted to a snark. This disproves two conjectures, one of which was first posed by Catlin et al. in [Congr. Num. 76:173–181, 1990] and in [J. Combin. Theory, Ser B 66:123–139, 1996], and was posed again by Li et al. in [Acta Math. Sin. English Ser 30(2):291–304, 2014] and by Yang in [Supereulerian graphs, hamiltonicity of graphs and several extremal problems in graphs, Ph. D. Dissertation, Université Paris-Sub, September 27, 2013], respectively, the other one was posed by Yang 2013.