{"title":"A small ultrafilter number at every singular cardinal","authors":"T. Benhamou, S. Jirattikansakul","doi":"10.1007/s10474-023-01377-9","DOIUrl":null,"url":null,"abstract":"<div><p>We obtain a small ultrafilter number at <span>\\(\\aleph_{\\omega_1}\\)</span>. Moreover, we develop a version of the overlapping strong extender forcing with collapses which can keep the top cardinal <span>\\(\\kappa\\)</span> inaccessible. We apply this forcing to construct a model where <span>\\(\\kappa\\)</span> is the least inaccessible and <span>\\( V_\\kappa \\)</span> is a model of GCH at regulars, failures of SCH at singulars, and the ultrafilter numbers at all singulars are small. \n</p></div>","PeriodicalId":50894,"journal":{"name":"Acta Mathematica Hungarica","volume":"171 1","pages":"12 - 38"},"PeriodicalIF":0.6000,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Acta Mathematica Hungarica","FirstCategoryId":"100","ListUrlMain":"https://link.springer.com/article/10.1007/s10474-023-01377-9","RegionNum":3,"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
We obtain a small ultrafilter number at \(\aleph_{\omega_1}\). Moreover, we develop a version of the overlapping strong extender forcing with collapses which can keep the top cardinal \(\kappa\) inaccessible. We apply this forcing to construct a model where \(\kappa\) is the least inaccessible and \( V_\kappa \) is a model of GCH at regulars, failures of SCH at singulars, and the ultrafilter numbers at all singulars are small.
期刊介绍:
Acta Mathematica Hungarica is devoted to publishing research articles of top quality in all areas of pure and applied mathematics as well as in theoretical computer science. The journal is published yearly in three volumes (two issues per volume, in total 6 issues) in both print and electronic formats. Acta Mathematica Hungarica (formerly Acta Mathematica Academiae Scientiarum Hungaricae) was founded in 1950 by the Hungarian Academy of Sciences.