The saturation number of W 4
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arXiv
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| Autores principales: | , , , |
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866909537529757696 |
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| author | Song, Ning Hu, Jinze Ji, Shengjin Cui, Qing |
| author_facet | Song, Ning Hu, Jinze Ji, Shengjin Cui, Qing |
| contents | For a fixed graph $H$, a graph $G$ is called $H$-saturated if $G$ does not contain $H$ as a (not necessarily induced) subgraph, but $G+e$ contains a copy of $H$ for any $e\in E(\overline{G})$. The saturation number of $H$, denoted by ${\rm sat}(n,H)$, is the minimum number of edges in an $n$-vertex $H$-saturated graph. A wheel $W_n$ is a graph obtained from a cycle of length $n$ by adding a new vertex and joining it to every vertex of the cycle. A well-known result of Erdős, Hajnal and Moon shows that ${\rm sat}(n,W_3)=2n-3$ for all $n\geq 4$ and $K_2\vee \overline{K_{n-2}}$ is the unique extremal graph, where $\vee$ denotes the graph join operation. In this paper, we study the saturation number of $W_4$. We prove that ${\rm sat}(n,W_4)=\lfloor\frac{5n-10}{2}\rfloor$ for all $n\geq 6$ and give a complete characterization of the extremal graphs. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_11473 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The saturation number of W 4 Song, Ning Hu, Jinze Ji, Shengjin Cui, Qing Combinatorics 05C35 For a fixed graph $H$, a graph $G$ is called $H$-saturated if $G$ does not contain $H$ as a (not necessarily induced) subgraph, but $G+e$ contains a copy of $H$ for any $e\in E(\overline{G})$. The saturation number of $H$, denoted by ${\rm sat}(n,H)$, is the minimum number of edges in an $n$-vertex $H$-saturated graph. A wheel $W_n$ is a graph obtained from a cycle of length $n$ by adding a new vertex and joining it to every vertex of the cycle. A well-known result of Erdős, Hajnal and Moon shows that ${\rm sat}(n,W_3)=2n-3$ for all $n\geq 4$ and $K_2\vee \overline{K_{n-2}}$ is the unique extremal graph, where $\vee$ denotes the graph join operation. In this paper, we study the saturation number of $W_4$. We prove that ${\rm sat}(n,W_4)=\lfloor\frac{5n-10}{2}\rfloor$ for all $n\geq 6$ and give a complete characterization of the extremal graphs. |
| title | The saturation number of W 4 |
| topic | Combinatorics 05C35 |
| url | https://arxiv.org/abs/2503.11473 |