<p>A matching <i>M</i> in a graph <i>G</i> is <i>connected</i> if the induced subgraph on the vertex set <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2971_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="70" /> </InlineMediaObject> <EquationSource Format="TEX">\(V(\{e,f\})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>V</mi> <mo stretchy="false">(</mo> <mo stretchy="false">{</mo> <mi>e</mi> <mo>,</mo> <mi>f</mi> <mo stretchy="false">}</mo> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> is connected for every pair of edges <i>e</i>,&#xa0;<i>f</i> in <i>M</i>. The problem of finding large connected matchings in graphs <i>G</i> with <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2971_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="68" /> </InlineMediaObject> <EquationSource Format="TEX">\(\alpha (G)=2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>α</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation> is closely related to Hadwiger’s conjecture for graphs with independence number 2. The problem of finding a large connected matching in a general graph is NP-hard. Füredi et al. in 2005 conjectured that each <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2971_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="57" /> </InlineMediaObject> <EquationSource Format="TEX">\((4t-1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mn>4</mn> <mi>t</mi> <mo>-</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>-vertex graph <i>G</i> with <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2971_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="68" /> </InlineMediaObject> <EquationSource Format="TEX">\(\alpha (G)=2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>α</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation> contains a connected matching of size at least <i>t</i>. Cambie recently showed that if this conjecture is false, then so is Hadwiger’s conjecture. In this paper, we present a number of properties possessed by a counterexample to Füredi et al.’s conjecture, and then using these properties, we prove that Füredi et al.’s conjecture holds for <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="373_2025_2971_Article_IEq5.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="47" /> </InlineMediaObject> <EquationSource Format="TEX">\(t\le 22\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>t</mi> <mo>≤</mo> <mn>22</mn> </mrow> </math></EquationSource> </InlineEquation>.</p>

错误:搜索内容不能为空,请输入英文关键词
错误:关键词超出字数限制,请精简
高级检索

Connected Matchings in Graphs with Independence Number Two

  • Rong Chen,
  • Zijian Deng

摘要

A matching M in a graph G is connected if the induced subgraph on the vertex set \(V(\{e,f\})\) V ( { e , f } ) is connected for every pair of edges ef in M. The problem of finding large connected matchings in graphs G with \(\alpha (G)=2\) α ( G ) = 2 is closely related to Hadwiger’s conjecture for graphs with independence number 2. The problem of finding a large connected matching in a general graph is NP-hard. Füredi et al. in 2005 conjectured that each \((4t-1)\) ( 4 t - 1 ) -vertex graph G with \(\alpha (G)=2\) α ( G ) = 2 contains a connected matching of size at least t. Cambie recently showed that if this conjecture is false, then so is Hadwiger’s conjecture. In this paper, we present a number of properties possessed by a counterexample to Füredi et al.’s conjecture, and then using these properties, we prove that Füredi et al.’s conjecture holds for \(t\le 22\) t 22 .