关于图形色度数的最大奇数诱导子图

Pub Date : 2024-07-09 DOI:10.1002/jgt.23148
Tao Wang, Baoyindureng Wu
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In 1992, Scott proposed a conjecture that <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <msub>\n <mi>f</mi>\n \n <mi>o</mi>\n </msub>\n \n <mrow>\n <mo>(</mo>\n \n <mi>G</mi>\n \n <mo>)</mo>\n </mrow>\n \n <mo>≥</mo>\n \n <mfrac>\n <mi>n</mi>\n \n <mrow>\n <mi>χ</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mi>G</mi>\n \n <mo>)</mo>\n </mrow>\n </mrow>\n </mfrac>\n </mrow>\n </mrow>\n <annotation> ${f}_{o}(G)\\ge \\frac{n}{\\chi (G)}$</annotation>\n </semantics></math> for a graph <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n <annotation> $G$</annotation>\n </semantics></math> of order <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>n</mi>\n </mrow>\n </mrow>\n <annotation> $n$</annotation>\n </semantics></math> without isolated vertices, where <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>χ</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mi>G</mi>\n \n <mo>)</mo>\n </mrow>\n </mrow>\n </mrow>\n <annotation> $\\chi (G)$</annotation>\n </semantics></math> is the chromatic number of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n <annotation> $G$</annotation>\n </semantics></math>. In this paper, we show that the conjecture is not true for bipartite graphs, but is true for all line graphs. In addition, we also disprove a conjecture of Berman, Wang, and Wargo in 1997, which states that <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <msub>\n <mi>f</mi>\n \n <mi>o</mi>\n </msub>\n \n <mrow>\n <mo>(</mo>\n \n <mi>G</mi>\n \n <mo>)</mo>\n </mrow>\n \n <mo>≥</mo>\n \n <mn>2</mn>\n \n <mfenced>\n <mfrac>\n <mi>n</mi>\n \n <mn>4</mn>\n </mfrac>\n </mfenced>\n </mrow>\n </mrow>\n <annotation> ${f}_{o}(G)\\ge 2\\unicode{x0230A}\\frac{n}{4}\\unicode{x0230B}$</annotation>\n </semantics></math> for a connected graph <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>G</mi>\n </mrow>\n </mrow>\n <annotation> $G$</annotation>\n </semantics></math> of order <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>n</mi>\n </mrow>\n </mrow>\n <annotation> $n$</annotation>\n </semantics></math>. Scott's conjecture is open for graphs with chromatic number at least 3.</p>","PeriodicalId":0,"journal":{"name":"","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Maximum odd induced subgraph of a graph concerning its chromatic number\",\"authors\":\"Tao Wang,&nbsp;Baoyindureng Wu\",\"doi\":\"10.1002/jgt.23148\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Let <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <msub>\\n <mi>f</mi>\\n \\n <mi>o</mi>\\n </msub>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>G</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow>\\n </mrow>\\n <annotation> ${f}_{o}(G)$</annotation>\\n </semantics></math> be the maximum order of an odd induced subgraph of <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n <annotation> $G$</annotation>\\n </semantics></math>. In 1992, Scott proposed a conjecture that <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <msub>\\n <mi>f</mi>\\n \\n <mi>o</mi>\\n </msub>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>G</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n \\n <mo>≥</mo>\\n \\n <mfrac>\\n <mi>n</mi>\\n \\n <mrow>\\n <mi>χ</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>G</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow>\\n </mfrac>\\n </mrow>\\n </mrow>\\n <annotation> ${f}_{o}(G)\\\\ge \\\\frac{n}{\\\\chi (G)}$</annotation>\\n </semantics></math> for a graph <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n <annotation> $G$</annotation>\\n </semantics></math> of order <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>n</mi>\\n </mrow>\\n </mrow>\\n <annotation> $n$</annotation>\\n </semantics></math> without isolated vertices, where <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>χ</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>G</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow>\\n </mrow>\\n <annotation> $\\\\chi (G)$</annotation>\\n </semantics></math> is the chromatic number of <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n <annotation> $G$</annotation>\\n </semantics></math>. In this paper, we show that the conjecture is not true for bipartite graphs, but is true for all line graphs. In addition, we also disprove a conjecture of Berman, Wang, and Wargo in 1997, which states that <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <msub>\\n <mi>f</mi>\\n \\n <mi>o</mi>\\n </msub>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>G</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n \\n <mo>≥</mo>\\n \\n <mn>2</mn>\\n \\n <mfenced>\\n <mfrac>\\n <mi>n</mi>\\n \\n <mn>4</mn>\\n </mfrac>\\n </mfenced>\\n </mrow>\\n </mrow>\\n <annotation> ${f}_{o}(G)\\\\ge 2\\\\unicode{x0230A}\\\\frac{n}{4}\\\\unicode{x0230B}$</annotation>\\n </semantics></math> for a connected graph <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>G</mi>\\n </mrow>\\n </mrow>\\n <annotation> $G$</annotation>\\n </semantics></math> of order <span></span><math>\\n <semantics>\\n <mrow>\\n \\n <mrow>\\n <mi>n</mi>\\n </mrow>\\n </mrow>\\n <annotation> $n$</annotation>\\n </semantics></math>. Scott's conjecture is open for graphs with chromatic number at least 3.</p>\",\"PeriodicalId\":0,\"journal\":{\"name\":\"\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0,\"publicationDate\":\"2024-07-09\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1002/jgt.23148\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"","FirstCategoryId":"100","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/jgt.23148","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0

摘要

让 是 .的奇数诱导子图的最大阶数。 1992 年,斯科特(Scott)提出了一个猜想:对于无孤立顶点的阶数图,让 是 .的色度数。 在本文中,我们证明了这一猜想对于二叉图并不成立,但对于所有线图都成立。此外,我们还推翻了 Berman、Wang 和 Wargo 于 1997 年提出的猜想,即对于秩为 .斯科特的猜想对于色度数至少为 3 的图是开放的。
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Maximum odd induced subgraph of a graph concerning its chromatic number

Let f o ( G ) ${f}_{o}(G)$ be the maximum order of an odd induced subgraph of G $G$ . In 1992, Scott proposed a conjecture that f o ( G ) n χ ( G ) ${f}_{o}(G)\ge \frac{n}{\chi (G)}$ for a graph G $G$ of order n $n$ without isolated vertices, where χ ( G ) $\chi (G)$ is the chromatic number of G $G$ . In this paper, we show that the conjecture is not true for bipartite graphs, but is true for all line graphs. In addition, we also disprove a conjecture of Berman, Wang, and Wargo in 1997, which states that f o ( G ) 2 n 4 ${f}_{o}(G)\ge 2\unicode{x0230A}\frac{n}{4}\unicode{x0230B}$ for a connected graph G $G$ of order n $n$ . Scott's conjecture is open for graphs with chromatic number at least 3.

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