{"title":"M, N, H","authors":"Will Brian , Alan Dow , Klaas Pieter Hart","doi":"10.1016/j.topol.2025.109539","DOIUrl":null,"url":null,"abstract":"<div><div>Let <span><math><mi>M</mi><mo>=</mo><mi>N</mi><mo>×</mo><mo>[</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>]</mo></math></span>. The natural projection <span><math><mi>π</mi><mo>:</mo><mi>M</mi><mo>→</mo><mi>N</mi></math></span>, which sends <span><math><mo>(</mo><mi>n</mi><mo>,</mo><mi>x</mi><mo>)</mo></math></span> to <em>n</em>, induces a projection mapping <span><math><msup><mrow><mi>π</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>:</mo><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>→</mo><msup><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>, where <span><math><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> and <span><math><msup><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> denote the Čech-Stone remainders of <span><math><mi>M</mi></math></span> and <span><math><mi>N</mi></math></span>, respectively.</div><div>We show that <span><math><mi>CH</mi></math></span> implies every autohomeomorphism of <span><math><msup><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> lifts through the natural projection to an autohomeomorphism of <span><math><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>. That is, for every homeomorphism <span><math><mi>h</mi><mo>:</mo><msup><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>→</mo><msup><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> there is a homeomorphism <span><math><mi>H</mi><mo>:</mo><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>→</mo><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> such that <span><math><msup><mrow><mi>π</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>∘</mo><mi>H</mi><mo>=</mo><mi>h</mi><mo>∘</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>. This complements a recent result of the second author, who showed that this lifting property is not a consequence of <span><math><mi>ZFC</mi></math></span>.</div><div>Combining this lifting theorem with a recent result of the first author, we also prove that <span><math><mi>CH</mi></math></span> implies there is an order-reversing autohomeomorphism of <span><math><msup><mrow><mi>H</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>, the Čech-Stone remainder of the half line <span><math><mi>H</mi><mo>=</mo><mo>[</mo><mn>0</mn><mo>,</mo><mo>∞</mo><mo>)</mo></math></span>.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"373 ","pages":"Article 109539"},"PeriodicalIF":0.5000,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"M⁎, N⁎, and H⁎\",\"authors\":\"Will Brian , Alan Dow , Klaas Pieter Hart\",\"doi\":\"10.1016/j.topol.2025.109539\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Let <span><math><mi>M</mi><mo>=</mo><mi>N</mi><mo>×</mo><mo>[</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>]</mo></math></span>. The natural projection <span><math><mi>π</mi><mo>:</mo><mi>M</mi><mo>→</mo><mi>N</mi></math></span>, which sends <span><math><mo>(</mo><mi>n</mi><mo>,</mo><mi>x</mi><mo>)</mo></math></span> to <em>n</em>, induces a projection mapping <span><math><msup><mrow><mi>π</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>:</mo><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>→</mo><msup><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>, where <span><math><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> and <span><math><msup><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> denote the Čech-Stone remainders of <span><math><mi>M</mi></math></span> and <span><math><mi>N</mi></math></span>, respectively.</div><div>We show that <span><math><mi>CH</mi></math></span> implies every autohomeomorphism of <span><math><msup><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> lifts through the natural projection to an autohomeomorphism of <span><math><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>. That is, for every homeomorphism <span><math><mi>h</mi><mo>:</mo><msup><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>→</mo><msup><mrow><mi>N</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> there is a homeomorphism <span><math><mi>H</mi><mo>:</mo><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>→</mo><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> such that <span><math><msup><mrow><mi>π</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>∘</mo><mi>H</mi><mo>=</mo><mi>h</mi><mo>∘</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>. This complements a recent result of the second author, who showed that this lifting property is not a consequence of <span><math><mi>ZFC</mi></math></span>.</div><div>Combining this lifting theorem with a recent result of the first author, we also prove that <span><math><mi>CH</mi></math></span> implies there is an order-reversing autohomeomorphism of <span><math><msup><mrow><mi>H</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>, the Čech-Stone remainder of the half line <span><math><mi>H</mi><mo>=</mo><mo>[</mo><mn>0</mn><mo>,</mo><mo>∞</mo><mo>)</mo></math></span>.</div></div>\",\"PeriodicalId\":51201,\"journal\":{\"name\":\"Topology and its Applications\",\"volume\":\"373 \",\"pages\":\"Article 109539\"},\"PeriodicalIF\":0.5000,\"publicationDate\":\"2025-08-08\",\"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/S0166864125003372\",\"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":"Topology and its Applications","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0166864125003372","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
Let . The natural projection , which sends to n, induces a projection mapping , where and denote the Čech-Stone remainders of and , respectively.
We show that implies every autohomeomorphism of lifts through the natural projection to an autohomeomorphism of . That is, for every homeomorphism there is a homeomorphism such that . This complements a recent result of the second author, who showed that this lifting property is not a consequence of .
Combining this lifting theorem with a recent result of the first author, we also prove that implies there is an order-reversing autohomeomorphism of , the Čech-Stone remainder of the half line .
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.