{"title":"群环中许多零除数所隐含的组合结果","authors":"Fedor Petrov","doi":"10.1134/S0016266324010076","DOIUrl":null,"url":null,"abstract":"<p> In a paper of Croot, Lev and Pach and a later paper of Ellenberg and Gijswijt, it was proved that for a group <span>\\(G=G_0^n\\)</span>, where <span>\\(G_0\\ne \\{1,-1\\}^m\\)</span> is a fixed finite Abelian group and <span>\\(n\\)</span> is large, any subset <span>\\(A\\subset G\\)</span> without 3-progressions (triples <span>\\(x\\)</span>, <span>\\(y\\)</span>, <span>\\(z\\)</span> of different elements with <span>\\(xy=z^2\\)</span>) contains at most <span>\\(|G|^{1-c}\\)</span> elements, where <span>\\(c>0\\)</span> is a constant depending only on <span>\\(G_0\\)</span>. This is known to be false when <span>\\(G\\)</span> is, say, a large cyclic group. The aim of this note is to show that the algebraic property corresponding to this difference is the following: in the first case, a group algebra <span>\\(\\mathbb{F}[G]\\)</span> over a suitable field <span>\\(\\mathbb{F}\\)</span> contains a subspace <span>\\(X\\)</span> with codimension at most <span>\\(|X|^{1-c}\\)</span> such that <span>\\(X^3=0\\)</span>. We discuss which bounds are obtained for finite Abelian <span>\\(p\\)</span>-groups and for some matrix <span>\\(p\\)</span>-groups: the Heisenberg group over <span>\\(\\mathbb{F}_p\\)</span> and the unitriangular group over <span>\\(\\mathbb{F}_p\\)</span>. We also show how the method allows us to generalize the results of [14] and [12]. </p>","PeriodicalId":575,"journal":{"name":"Functional Analysis and Its Applications","volume":"58 1","pages":"80 - 89"},"PeriodicalIF":0.6000,"publicationDate":"2024-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Combinatorial Results Implied by Many Zero Divisors in a Group Ring\",\"authors\":\"Fedor Petrov\",\"doi\":\"10.1134/S0016266324010076\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p> In a paper of Croot, Lev and Pach and a later paper of Ellenberg and Gijswijt, it was proved that for a group <span>\\\\(G=G_0^n\\\\)</span>, where <span>\\\\(G_0\\\\ne \\\\{1,-1\\\\}^m\\\\)</span> is a fixed finite Abelian group and <span>\\\\(n\\\\)</span> is large, any subset <span>\\\\(A\\\\subset G\\\\)</span> without 3-progressions (triples <span>\\\\(x\\\\)</span>, <span>\\\\(y\\\\)</span>, <span>\\\\(z\\\\)</span> of different elements with <span>\\\\(xy=z^2\\\\)</span>) contains at most <span>\\\\(|G|^{1-c}\\\\)</span> elements, where <span>\\\\(c>0\\\\)</span> is a constant depending only on <span>\\\\(G_0\\\\)</span>. This is known to be false when <span>\\\\(G\\\\)</span> is, say, a large cyclic group. The aim of this note is to show that the algebraic property corresponding to this difference is the following: in the first case, a group algebra <span>\\\\(\\\\mathbb{F}[G]\\\\)</span> over a suitable field <span>\\\\(\\\\mathbb{F}\\\\)</span> contains a subspace <span>\\\\(X\\\\)</span> with codimension at most <span>\\\\(|X|^{1-c}\\\\)</span> such that <span>\\\\(X^3=0\\\\)</span>. We discuss which bounds are obtained for finite Abelian <span>\\\\(p\\\\)</span>-groups and for some matrix <span>\\\\(p\\\\)</span>-groups: the Heisenberg group over <span>\\\\(\\\\mathbb{F}_p\\\\)</span> and the unitriangular group over <span>\\\\(\\\\mathbb{F}_p\\\\)</span>. We also show how the method allows us to generalize the results of [14] and [12]. </p>\",\"PeriodicalId\":575,\"journal\":{\"name\":\"Functional Analysis and Its Applications\",\"volume\":\"58 1\",\"pages\":\"80 - 89\"},\"PeriodicalIF\":0.6000,\"publicationDate\":\"2024-05-16\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Functional Analysis and Its Applications\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://link.springer.com/article/10.1134/S0016266324010076\",\"RegionNum\":4,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Functional Analysis and Its Applications","FirstCategoryId":"100","ListUrlMain":"https://link.springer.com/article/10.1134/S0016266324010076","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
Combinatorial Results Implied by Many Zero Divisors in a Group Ring
In a paper of Croot, Lev and Pach and a later paper of Ellenberg and Gijswijt, it was proved that for a group \(G=G_0^n\), where \(G_0\ne \{1,-1\}^m\) is a fixed finite Abelian group and \(n\) is large, any subset \(A\subset G\) without 3-progressions (triples \(x\), \(y\), \(z\) of different elements with \(xy=z^2\)) contains at most \(|G|^{1-c}\) elements, where \(c>0\) is a constant depending only on \(G_0\). This is known to be false when \(G\) is, say, a large cyclic group. The aim of this note is to show that the algebraic property corresponding to this difference is the following: in the first case, a group algebra \(\mathbb{F}[G]\) over a suitable field \(\mathbb{F}\) contains a subspace \(X\) with codimension at most \(|X|^{1-c}\) such that \(X^3=0\). We discuss which bounds are obtained for finite Abelian \(p\)-groups and for some matrix \(p\)-groups: the Heisenberg group over \(\mathbb{F}_p\) and the unitriangular group over \(\mathbb{F}_p\). We also show how the method allows us to generalize the results of [14] and [12].
期刊介绍:
Functional Analysis and Its Applications publishes current problems of functional analysis, including representation theory, theory of abstract and functional spaces, theory of operators, spectral theory, theory of operator equations, and the theory of normed rings. The journal also covers the most important applications of functional analysis in mathematics, mechanics, and theoretical physics.