{"title":"Countably tight, zero-dimensional and totally disconnected dense subspaces of Cp(X)","authors":"Joel Aguilar-Velázquez , Reynaldo Rojas-Hernández","doi":"10.1016/j.topol.2025.109220","DOIUrl":null,"url":null,"abstract":"<div><div>In this paper we prove that under <em>CH</em> there exists a space <em>X</em> such that <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span> does not admit dense subspaces of countable tightness, partially answering Problem 1 of <span><span>[13]</span></span>. We prove that if <em>X</em> has cardinality at most continuum, then <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span> contains a dense zero-dimensional subspace and a dense totally disconnected non zero-dimensional subspace. We also provide an example of a compact space <em>X</em> such that <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>(</mo><mi>X</mi><mo>,</mo><mn>2</mn><mo>)</mo></math></span> is exponentially separable but <em>X</em> is not Corson compact.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"362 ","pages":"Article 109220"},"PeriodicalIF":0.6000,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Topology and its Applications","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0166864125000185","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
In this paper we prove that under CH there exists a space X such that does not admit dense subspaces of countable tightness, partially answering Problem 1 of [13]. We prove that if X has cardinality at most continuum, then contains a dense zero-dimensional subspace and a dense totally disconnected non zero-dimensional subspace. We also provide an example of a compact space X such that is exponentially separable but X is not Corson compact.
期刊介绍:
Topology and its Applications is primarily concerned with publishing original research papers of moderate length. However, a limited number of carefully selected survey or expository papers are also included. The mathematical focus of the journal is that suggested by the title: Research in Topology. It is felt that it is inadvisable to attempt a definitive description of topology as understood for this journal. Certainly the subject includes the algebraic, general, geometric, and set-theoretic facets of topology as well as areas of interactions between topology and other mathematical disciplines, e.g. topological algebra, topological dynamics, functional analysis, category theory. Since the roles of various aspects of topology continue to change, the non-specific delineation of topics serves to reflect the current state of research in topology.
At regular intervals, the journal publishes a section entitled Open Problems in Topology, edited by J. van Mill and G.M. Reed. This is a status report on the 1100 problems listed in the book of the same name published by North-Holland in 1990, edited by van Mill and Reed.