{"title":"Towards Nash-Williams orientation conjecture for infinite graphs","authors":"Amena Assem","doi":"10.1002/jgt.23192","DOIUrl":null,"url":null,"abstract":"<p>In 1960 Nash-Williams proved that an edge-connectivity of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mn>2</mn>\n \n <mi>k</mi>\n </mrow>\n </mrow>\n <annotation> <math xmlns=\"http://www.w3.org/1998/Math/MathML\" altimg=\"urn:x-wiley:03649024:media:jgt23192:jgt23192-math-0001\" wiley:location=\"equation/jgt23192-math-0001.png\"><mrow><mrow><mn>2</mn><mi>k</mi></mrow></mrow></math></annotation>\n </semantics></math> is sufficient for a finite graph to have a <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>k</mi>\n </mrow>\n </mrow>\n <annotation> <math xmlns=\"http://www.w3.org/1998/Math/MathML\" altimg=\"urn:x-wiley:03649024:media:jgt23192:jgt23192-math-0002\" wiley:location=\"equation/jgt23192-math-0002.png\"><mrow><mrow><mi>k</mi></mrow></mrow></math></annotation>\n </semantics></math>-arc-connected orientation. He then conjectured that the same is true for infinite graphs. In 2016, Thomassen, using his own results on the auxiliary <i>lifting graph</i>, proved that <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mn>8</mn>\n \n <mi>k</mi>\n </mrow>\n </mrow>\n <annotation> <math xmlns=\"http://www.w3.org/1998/Math/MathML\" altimg=\"urn:x-wiley:03649024:media:jgt23192:jgt23192-math-0003\" wiley:location=\"equation/jgt23192-math-0003.png\"><mrow><mrow><mn>8</mn><mi>k</mi></mrow></mrow></math></annotation>\n </semantics></math>-edge-connected infinite graphs admit a <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mi>k</mi>\n </mrow>\n </mrow>\n <annotation> <math xmlns=\"http://www.w3.org/1998/Math/MathML\" altimg=\"urn:x-wiley:03649024:media:jgt23192:jgt23192-math-0004\" wiley:location=\"equation/jgt23192-math-0004.png\"><mrow><mrow><mi>k</mi></mrow></mrow></math></annotation>\n </semantics></math>-arc-connected orientation. Here we improve this result for the class of one-ended locally finite graphs and show that an edge-connectivity of <span></span><math>\n <semantics>\n <mrow>\n \n <mrow>\n <mn>4</mn>\n \n <mi>k</mi>\n </mrow>\n </mrow>\n <annotation> <math xmlns=\"http://www.w3.org/1998/Math/MathML\" altimg=\"urn:x-wiley:03649024:media:jgt23192:jgt23192-math-0005\" wiley:location=\"equation/jgt23192-math-0005.png\"><mrow><mrow><mn>4</mn><mi>k</mi></mrow></mrow></math></annotation>\n </semantics></math> is enough in that case. Crucial to this improvement are results presented in a separate paper, by the same author of this paper, on the key concept of the lifting graph, extending results by Ok, Richter, and Thomassen.</p>","PeriodicalId":16014,"journal":{"name":"Journal of Graph Theory","volume":"108 3","pages":"608-619"},"PeriodicalIF":0.9000,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jgt.23192","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Graph Theory","FirstCategoryId":"100","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/jgt.23192","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
In 1960 Nash-Williams proved that an edge-connectivity of is sufficient for a finite graph to have a -arc-connected orientation. He then conjectured that the same is true for infinite graphs. In 2016, Thomassen, using his own results on the auxiliary lifting graph, proved that -edge-connected infinite graphs admit a -arc-connected orientation. Here we improve this result for the class of one-ended locally finite graphs and show that an edge-connectivity of is enough in that case. Crucial to this improvement are results presented in a separate paper, by the same author of this paper, on the key concept of the lifting graph, extending results by Ok, Richter, and Thomassen.
期刊介绍:
The Journal of Graph Theory is devoted to a variety of topics in graph theory, such as structural results about graphs, graph algorithms with theoretical emphasis, and discrete optimization on graphs. The scope of the journal also includes related areas in combinatorics and the interaction of graph theory with other mathematical sciences.
A subscription to the Journal of Graph Theory includes a subscription to the Journal of Combinatorial Designs .