{"title":"避免无限序列仿射副本的大集合","authors":"Angel D. Cruz, Chun-Kit Lai, Malabika Pramanik","doi":"10.14321/realanalexch.48.2.1681628520","DOIUrl":null,"url":null,"abstract":"A conjecture of Erdös states that for any infinite set $A \\subseteq \\mathbb R$, there exists a Borel set $E \\subseteq \\mathbb R$ of positive Lebesgue measure that does not contain any non-trivial affine copy of $A$. The conjecture remains open for most fast-decaying sequences, including the geometric sequence $A = \\{2^{-k} : k \\geq 1\\}$. In this article, we consider infinite decreasing sequences $A = \\{a_k: k \\geq 1\\}$ in $\\R$ that converge to zero at a prescribed rate; namely $\\log (a_n/a_{n+1}) = e^{\\varphi(n)} $, where $\\varphi(n)/n\\to 0$ as $n\\to\\infty$. This condition is satisfied by sequences whose logarithm has polynomial decay, and in particular by the geometric sequence. For any such sequence $A$, we construct a Cantor set $K \\subseteq \\mathbb [0,1]$ with measure arbitrarily close to 1, such that the set of Erdös points $\\mathcal{E}\\subseteq K$ has Hasudorff dimension 1.","PeriodicalId":44674,"journal":{"name":"Real Analysis Exchange","volume":"33 1","pages":"0"},"PeriodicalIF":0.1000,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Large Sets Avoiding Affine Copies of Infinite Sequences\",\"authors\":\"Angel D. Cruz, Chun-Kit Lai, Malabika Pramanik\",\"doi\":\"10.14321/realanalexch.48.2.1681628520\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"A conjecture of Erdös states that for any infinite set $A \\\\subseteq \\\\mathbb R$, there exists a Borel set $E \\\\subseteq \\\\mathbb R$ of positive Lebesgue measure that does not contain any non-trivial affine copy of $A$. The conjecture remains open for most fast-decaying sequences, including the geometric sequence $A = \\\\{2^{-k} : k \\\\geq 1\\\\}$. In this article, we consider infinite decreasing sequences $A = \\\\{a_k: k \\\\geq 1\\\\}$ in $\\\\R$ that converge to zero at a prescribed rate; namely $\\\\log (a_n/a_{n+1}) = e^{\\\\varphi(n)} $, where $\\\\varphi(n)/n\\\\to 0$ as $n\\\\to\\\\infty$. This condition is satisfied by sequences whose logarithm has polynomial decay, and in particular by the geometric sequence. For any such sequence $A$, we construct a Cantor set $K \\\\subseteq \\\\mathbb [0,1]$ with measure arbitrarily close to 1, such that the set of Erdös points $\\\\mathcal{E}\\\\subseteq K$ has Hasudorff dimension 1.\",\"PeriodicalId\":44674,\"journal\":{\"name\":\"Real Analysis Exchange\",\"volume\":\"33 1\",\"pages\":\"0\"},\"PeriodicalIF\":0.1000,\"publicationDate\":\"2023-10-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Real Analysis Exchange\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.14321/realanalexch.48.2.1681628520\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Real Analysis Exchange","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.14321/realanalexch.48.2.1681628520","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATHEMATICS","Score":null,"Total":0}
Large Sets Avoiding Affine Copies of Infinite Sequences
A conjecture of Erdös states that for any infinite set $A \subseteq \mathbb R$, there exists a Borel set $E \subseteq \mathbb R$ of positive Lebesgue measure that does not contain any non-trivial affine copy of $A$. The conjecture remains open for most fast-decaying sequences, including the geometric sequence $A = \{2^{-k} : k \geq 1\}$. In this article, we consider infinite decreasing sequences $A = \{a_k: k \geq 1\}$ in $\R$ that converge to zero at a prescribed rate; namely $\log (a_n/a_{n+1}) = e^{\varphi(n)} $, where $\varphi(n)/n\to 0$ as $n\to\infty$. This condition is satisfied by sequences whose logarithm has polynomial decay, and in particular by the geometric sequence. For any such sequence $A$, we construct a Cantor set $K \subseteq \mathbb [0,1]$ with measure arbitrarily close to 1, such that the set of Erdös points $\mathcal{E}\subseteq K$ has Hasudorff dimension 1.