{"title":"Zpk 中权重为零的有向循环","authors":"Shoham Letzter , Natasha Morrison","doi":"10.1016/j.jctb.2024.05.002","DOIUrl":null,"url":null,"abstract":"<div><p>For a finite abelian group <em>A</em>, define <span><math><mi>f</mi><mo>(</mo><mi>A</mi><mo>)</mo></math></span> to be the minimum integer such that for every complete digraph Γ on <em>f</em> vertices and every map <span><math><mi>w</mi><mo>:</mo><mi>E</mi><mo>(</mo><mi>Γ</mi><mo>)</mo><mo>→</mo><mi>A</mi></math></span>, there exists a directed cycle <em>C</em> in Γ such that <span><math><msub><mrow><mo>∑</mo></mrow><mrow><mi>e</mi><mo>∈</mo><mi>E</mi><mo>(</mo><mi>C</mi><mo>)</mo></mrow></msub><mi>w</mi><mo>(</mo><mi>e</mi><mo>)</mo><mo>=</mo><mn>0</mn></math></span>. The study of <span><math><mi>f</mi><mo>(</mo><mi>A</mi><mo>)</mo></math></span> was initiated by Alon and Krivelevich (2021). In this article, we prove that <span><math><mi>f</mi><mo>(</mo><msubsup><mrow><mi>Z</mi></mrow><mrow><mi>p</mi></mrow><mrow><mi>k</mi></mrow></msubsup><mo>)</mo><mo>=</mo><mi>O</mi><mo>(</mo><mi>p</mi><mi>k</mi><msup><mrow><mo>(</mo><mi>log</mi><mo></mo><mi>k</mi><mo>)</mo></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math></span>, where <em>p</em> is prime, with an improved bound of <span><math><mi>O</mi><mo>(</mo><mi>k</mi><mi>log</mi><mo></mo><mi>k</mi><mo>)</mo></math></span> when <span><math><mi>p</mi><mo>=</mo><mn>2</mn></math></span>. These bounds are tight up to a factor which is polylogarithmic in <em>k</em>.</p></div>","PeriodicalId":54865,"journal":{"name":"Journal of Combinatorial Theory Series B","volume":"168 ","pages":"Pages 192-207"},"PeriodicalIF":1.2000,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0095895624000418/pdfft?md5=5e9d14a46eed8e2ee2946b39a3ab2037&pid=1-s2.0-S0095895624000418-main.pdf","citationCount":"0","resultStr":"{\"title\":\"Directed cycles with zero weight in Zpk\",\"authors\":\"Shoham Letzter , Natasha Morrison\",\"doi\":\"10.1016/j.jctb.2024.05.002\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>For a finite abelian group <em>A</em>, define <span><math><mi>f</mi><mo>(</mo><mi>A</mi><mo>)</mo></math></span> to be the minimum integer such that for every complete digraph Γ on <em>f</em> vertices and every map <span><math><mi>w</mi><mo>:</mo><mi>E</mi><mo>(</mo><mi>Γ</mi><mo>)</mo><mo>→</mo><mi>A</mi></math></span>, there exists a directed cycle <em>C</em> in Γ such that <span><math><msub><mrow><mo>∑</mo></mrow><mrow><mi>e</mi><mo>∈</mo><mi>E</mi><mo>(</mo><mi>C</mi><mo>)</mo></mrow></msub><mi>w</mi><mo>(</mo><mi>e</mi><mo>)</mo><mo>=</mo><mn>0</mn></math></span>. The study of <span><math><mi>f</mi><mo>(</mo><mi>A</mi><mo>)</mo></math></span> was initiated by Alon and Krivelevich (2021). In this article, we prove that <span><math><mi>f</mi><mo>(</mo><msubsup><mrow><mi>Z</mi></mrow><mrow><mi>p</mi></mrow><mrow><mi>k</mi></mrow></msubsup><mo>)</mo><mo>=</mo><mi>O</mi><mo>(</mo><mi>p</mi><mi>k</mi><msup><mrow><mo>(</mo><mi>log</mi><mo></mo><mi>k</mi><mo>)</mo></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math></span>, where <em>p</em> is prime, with an improved bound of <span><math><mi>O</mi><mo>(</mo><mi>k</mi><mi>log</mi><mo></mo><mi>k</mi><mo>)</mo></math></span> when <span><math><mi>p</mi><mo>=</mo><mn>2</mn></math></span>. These bounds are tight up to a factor which is polylogarithmic in <em>k</em>.</p></div>\",\"PeriodicalId\":54865,\"journal\":{\"name\":\"Journal of Combinatorial Theory Series B\",\"volume\":\"168 \",\"pages\":\"Pages 192-207\"},\"PeriodicalIF\":1.2000,\"publicationDate\":\"2024-05-29\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.sciencedirect.com/science/article/pii/S0095895624000418/pdfft?md5=5e9d14a46eed8e2ee2946b39a3ab2037&pid=1-s2.0-S0095895624000418-main.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Combinatorial Theory Series B\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0095895624000418\",\"RegionNum\":1,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Combinatorial Theory Series B","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0095895624000418","RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
摘要
对于有限无边群 A,定义 f(A) 为最小整数,即对于 f 个顶点上的每个完整图 Γ 和每个映射 w:E(Γ)→A, Γ 中存在一个有向循环 C,使得∑e∈E(C)w(e)=0。 f(A) 的研究由 Alon 和 Krivelevich (2021) 发起。在这篇文章中,我们证明了 f(Zpk)=O(pk(logk)2),其中 p 是素数,当 p=2 时的改进边界为 O(klogk)。这些界值在 k 的多对数因子以内都很紧。
For a finite abelian group A, define to be the minimum integer such that for every complete digraph Γ on f vertices and every map , there exists a directed cycle C in Γ such that . The study of was initiated by Alon and Krivelevich (2021). In this article, we prove that , where p is prime, with an improved bound of when . These bounds are tight up to a factor which is polylogarithmic in k.
期刊介绍:
The Journal of Combinatorial Theory publishes original mathematical research dealing with theoretical and physical aspects of the study of finite and discrete structures in all branches of science. Series B is concerned primarily with graph theory and matroid theory and is a valuable tool for mathematicians and computer scientists.