{"title":"理想极限点的拓扑复杂性","authors":"Marek Balcerzak, Szymon Glab, Paolo Leonetti","doi":"arxiv-2407.12160","DOIUrl":null,"url":null,"abstract":"Given an ideal $\\mathcal{I}$ on the nonnegative integers $\\omega$ and a\nPolish space $X$, let $\\mathscr{L}(\\mathcal{I})$ be the family of subsets\n$S\\subseteq X$ such that $S$ is the set of $\\mathcal{I}$-limit points of some\nsequence taking values in $X$. First, we show that $\\mathscr{L}(\\mathcal{I})$\nmay attain arbitrarily large Borel complexity. Second, we prove that if\n$\\mathcal{I}$ is a $G_{\\delta\\sigma}$-ideal then all elements of\n$\\mathscr{L}(\\mathcal{I})$ are closed. Third, we show that if $\\mathcal{I}$ is\na simply coanalytic ideal and $X$ is first countable, then every element of\n$\\mathscr{L}(\\mathcal{I})$ is simply analytic. Lastly, we studied certain\nstructural properties and the topological complexity of minimal ideals\n$\\mathcal{I}$ for which $\\mathscr{L}(\\mathcal{I})$ contains a given set.","PeriodicalId":501314,"journal":{"name":"arXiv - MATH - General Topology","volume":"48 15 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Topological complexity of ideal limit points\",\"authors\":\"Marek Balcerzak, Szymon Glab, Paolo Leonetti\",\"doi\":\"arxiv-2407.12160\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Given an ideal $\\\\mathcal{I}$ on the nonnegative integers $\\\\omega$ and a\\nPolish space $X$, let $\\\\mathscr{L}(\\\\mathcal{I})$ be the family of subsets\\n$S\\\\subseteq X$ such that $S$ is the set of $\\\\mathcal{I}$-limit points of some\\nsequence taking values in $X$. First, we show that $\\\\mathscr{L}(\\\\mathcal{I})$\\nmay attain arbitrarily large Borel complexity. Second, we prove that if\\n$\\\\mathcal{I}$ is a $G_{\\\\delta\\\\sigma}$-ideal then all elements of\\n$\\\\mathscr{L}(\\\\mathcal{I})$ are closed. Third, we show that if $\\\\mathcal{I}$ is\\na simply coanalytic ideal and $X$ is first countable, then every element of\\n$\\\\mathscr{L}(\\\\mathcal{I})$ is simply analytic. Lastly, we studied certain\\nstructural properties and the topological complexity of minimal ideals\\n$\\\\mathcal{I}$ for which $\\\\mathscr{L}(\\\\mathcal{I})$ contains a given set.\",\"PeriodicalId\":501314,\"journal\":{\"name\":\"arXiv - MATH - General Topology\",\"volume\":\"48 15 1\",\"pages\":\"\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2024-07-16\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"arXiv - MATH - General Topology\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/arxiv-2407.12160\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv - MATH - General Topology","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/arxiv-2407.12160","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
Given an ideal $\mathcal{I}$ on the nonnegative integers $\omega$ and a
Polish space $X$, let $\mathscr{L}(\mathcal{I})$ be the family of subsets
$S\subseteq X$ such that $S$ is the set of $\mathcal{I}$-limit points of some
sequence taking values in $X$. First, we show that $\mathscr{L}(\mathcal{I})$
may attain arbitrarily large Borel complexity. Second, we prove that if
$\mathcal{I}$ is a $G_{\delta\sigma}$-ideal then all elements of
$\mathscr{L}(\mathcal{I})$ are closed. Third, we show that if $\mathcal{I}$ is
a simply coanalytic ideal and $X$ is first countable, then every element of
$\mathscr{L}(\mathcal{I})$ is simply analytic. Lastly, we studied certain
structural properties and the topological complexity of minimal ideals
$\mathcal{I}$ for which $\mathscr{L}(\mathcal{I})$ contains a given set.