{"title":"On a Clique-Building Game of Erdős","authors":"Alexandru Malekshahian, Sam Spiro","doi":"10.1002/jgt.70061","DOIUrl":"https://doi.org/10.1002/jgt.70061","url":null,"abstract":"<p>The following game was introduced in a list of open problems from 1983 attributed to Erdős: two players take turns claiming edges of a <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 \u0000 <mrow>\u0000 <msub>\u0000 <mi>K</mi>\u0000 \u0000 <mi>n</mi>\u0000 </msub>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> <math xmlns=\"http://www.w3.org/1998/Math/MathML\" altimg=\"urn:x-wiley:03649024:media:jgt70061:jgt70061-math-0001\" wiley:location=\"equation/jgt70061-math-0001.png\"><mrow><mrow><msub><mi>K</mi><mi>n</mi></msub></mrow></mrow></math></annotation>\u0000 </semantics></math> until all edges are exhausted. Player 1 wins the game if the largest clique that they claim at the end is strictly larger than the largest clique of their opponent; otherwise, Player 2 wins the game. Erdős conjectured that Player 2 always wins this game for <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 \u0000 <mrow>\u0000 <mi>n</mi>\u0000 \u0000 <mo>≥</mo>\u0000 \u0000 <mn>3</mn>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> <math xmlns=\"http://www.w3.org/1998/Math/MathML\" altimg=\"urn:x-wiley:03649024:media:jgt70061:jgt70061-math-0002\" wiley:location=\"equation/jgt70061-math-0002.png\"><mrow><mrow><mi>n</mi><mo>unicode{x02265}</mo><mn>3</mn></mrow></mrow></math></annotation>\u0000 </semantics></math>. We make the first known progress on this problem, proving that this holds for at least 3/4 of all such <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 \u0000 <mrow>\u0000 <mi>n</mi>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> <math xmlns=\"http://www.w3.org/1998/Math/MathML\" altimg=\"urn:x-wiley:03649024:media:jgt70061:jgt70061-math-0003\" wiley:location=\"equation/jgt70061-math-0003.png\"><mrow><mrow><mi>n</mi></mrow></mrow></math></annotation>\u0000 </semantics></math>. We also address a biased version of this game, as well as the corresponding degree-building game, both of which were originally proposed by Erdős as well.</p>","PeriodicalId":16014,"journal":{"name":"Journal of Graph Theory","volume":"113 2","pages":"208-221"},"PeriodicalIF":1.0,"publicationDate":"2026-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jgt.70061","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148704252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stefanie Gerke, Gregory Gutin, Anders Yeo, Yacong Zhou
{"title":"Lower Bounds for Maximum Weight Bisections of Weighted Triangle-Free Subcubic Graphs","authors":"Stefanie Gerke, Gregory Gutin, Anders Yeo, Yacong Zhou","doi":"10.1002/jgt.70056","DOIUrl":"https://doi.org/10.1002/jgt.70056","url":null,"abstract":"<p>A bisection of a graph is a cut in which the number of vertices in the two parts of the cut differ by at most 1. In this paper, we consider maximum weight bisections of edge-weighted triangle-free subcubic graphs and show that every weighted triangle-free subcubic graph <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 \u0000 <mi>G</mi>\u0000 \u0000 <mo>=</mo>\u0000 \u0000 <mrow>\u0000 <mo>(</mo>\u0000 \u0000 <mrow>\u0000 <mi>V</mi>\u0000 \u0000 <mo>,</mo>\u0000 \u0000 <mi>E</mi>\u0000 \u0000 <mo>,</mo>\u0000 \u0000 <mi>w</mi>\u0000 </mrow>\u0000 \u0000 <mo>)</mo>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> <math xmlns=\"http://www.w3.org/1998/Math/MathML\" altimg=\"urn:x-wiley:03649024:media:jgt70056:jgt70056-math-0001\" wiley:location=\"equation/jgt70056-math-0001.png\"><mrow><mi>G</mi><mo>=</mo><mrow><mo>(</mo><mrow><mi>V</mi><mo>,</mo><mi>E</mi><mo>,</mo><mi>w</mi></mrow><mo>)</mo></mrow></mrow></math></annotation>\u0000 </semantics></math> has a bisection with weight at least <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 \u0000 <mi>θ</mi>\u0000 \u0000 <mo>⋅</mo>\u0000 \u0000 <mi>w</mi>\u0000 \u0000 <mrow>\u0000 <mo>(</mo>\u0000 \u0000 <mi>G</mi>\u0000 \u0000 <mo>)</mo>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> <math xmlns=\"http://www.w3.org/1998/Math/MathML\" altimg=\"urn:x-wiley:03649024:media:jgt70056:jgt70056-math-0002\" wiley:location=\"equation/jgt70056-math-0002.png\"><mrow><mi>unicode{x003B8}</mi><mo>unicode{x022C5}</mo><mi>w</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></annotation>\u0000 </semantics></math> unless <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 \u0000 <mi>G</mi>\u0000 \u0000 <mo>≅</mo>\u0000 \u0000 <msub>\u0000 <mi>K</mi>\u0000 \u0000 <mrow>\u0000 <mn>1</mn>\u0000 \u0000 ","PeriodicalId":16014,"journal":{"name":"Journal of Graph Theory","volume":"113 2","pages":"252-273"},"PeriodicalIF":1.0,"publicationDate":"2026-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jgt.70056","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148704253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wanying Huang, David Hume, Samuel J. Kelly, Ryan Lam
{"title":"A Coarse Geometric Approach to Graph Layout Problems","authors":"Wanying Huang, David Hume, Samuel J. Kelly, Ryan Lam","doi":"10.1002/jgt.70058","DOIUrl":"https://doi.org/10.1002/jgt.70058","url":null,"abstract":"<p>We define a range of new coarse geometric invariants based on various graph–theoretic measures of complexity for finite graphs, including treewidth, pathwidth, cutwidth and bandwidth. We prove that, for bounded degree graphs, these invariants can be used to define functions which satisfy a strong monotonicity property, namely, they are monotonically nondecreasing with respect to a large-scale geometric generalisation of graph inclusion, and as such have potential applications in coarse geometry and geometric group theory. On the graph–theoretic side, we prove asymptotically optimal bounds on most of the above widths for the family of all finite subgraphs of any bounded degree graph whose separation profile is known to be of the form <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 \u0000 <mrow>\u0000 <msup>\u0000 <mi>r</mi>\u0000 \u0000 <mi>a</mi>\u0000 </msup>\u0000 \u0000 <mi>log</mi>\u0000 \u0000 <msup>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 \u0000 <mi>r</mi>\u0000 \u0000 <mo>)</mo>\u0000 </mrow>\u0000 \u0000 <mi>b</mi>\u0000 </msup>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> <math display=\"inline\" altimg=\"urn:x-wiley:03649024:media:jgt70058:jgt70058-math-0001\" xmlns=\"http://www.w3.org/1998/Math/MathML\" wiley:location=\"equation/jgt70058-math-0001.png\"><mrow><mrow><msup><mi>r</mi><mi>a</mi></msup><mi>log</mi><msup><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mi>b</mi></msup></mrow></mrow></math></annotation>\u0000 </semantics></math> for some <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 \u0000 <mrow>\u0000 <mi>a</mi>\u0000 \u0000 <mo>></mo>\u0000 \u0000 <mn>0</mn>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> <math display=\"inline\" altimg=\"urn:x-wiley:03649024:media:jgt70058:jgt70058-math-0002\" xmlns=\"http://www.w3.org/1998/Math/MathML\" wiley:location=\"equation/jgt70058-math-0002.png\"><mrow><mrow><mi>a</mi><mo>unicode{x0003E}</mo><mn>0</mn></mrow></mrow></math></annotation>\u0000 </semantics></math>. This large class includes Diestel–Leader graphs, all Cayley graphs of nonvirtually cyclic polycyclic groups, uniform lattices in","PeriodicalId":16014,"journal":{"name":"Journal of Graph Theory","volume":"113 2","pages":"169-194"},"PeriodicalIF":1.0,"publicationDate":"2026-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jgt.70058","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148704458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}