{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2023,10,5]],"date-time":"2023-10-05T06:11:37Z","timestamp":1696486297311},"reference-count":11,"publisher":"Wiley","issue":"3","license":[{"start":{"date-parts":[[2016,5,27]],"date-time":"2016-05-27T00:00:00Z","timestamp":1464307200000},"content-version":"vor","delay-in-days":26,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"name":"Russian Foundation for Basic Research","award":["14-01-93105","16-01-00615"],"award-info":[{"award-number":["14-01-93105","16-01-00615"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Mathematical Logic Qtrly"],"published-print":{"date-parts":[[2016,5]]},"abstract":"<jats:p>In set theory without the Axiom of Choice <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0001.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0001\" \/>, we study the deductive strength of the statements <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0002.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0002\" \/> (\u201cEvery partially ordered set without a maximal element has two disjoint cofinal subsets\u201d), <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0003.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0003\" \/> (\u201cEvery partially ordered set without a maximal element has a countably infinite disjoint family of cofinal subsets\u201d), <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0004.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0004\" \/> (\u201cEvery linearly ordered set without a maximum element has two disjoint cofinal subsets\u201d), and <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0005.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0005\" \/> (\u201cEvery linearly ordered set without a maximum element has a countably infinite disjoint family of cofinal subsets\u201d).\nAmong various results, we prove that none of the above statements is provable without using some form of choice, <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0006.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0006\" \/> is equivalent to <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0007.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0007\" \/>, <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0008.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0008\" \/> + <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0009.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0009\" \/> (Dependent Choices) implies <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0010.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0010\" \/>, <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0011.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0011\" \/> does not imply <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0012.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0012\" \/> in <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0013.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0013\" \/> (Zermelo\u2010Fraenkel set theory with the Axiom of Extensionality modified in order to allow the existence of atoms), <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0014.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0014\" \/> does not imply <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0015.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0015\" \/> in <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0016.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0016\" \/> (Zermelo\u2010Fraenkel set theory minus <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0017.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0017\" \/>) and <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0018.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0018\" \/> (hence, <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0019.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0019\" \/>) is strictly weaker than <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0020.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0020\" \/> in <jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/malq201400089-math-0021.png\" xlink:title=\"urn:x-wiley:09425616:media:malq201400089:malq201400089-math-0021\" \/>.<\/jats:p>","DOI":"10.1002\/malq.201400089","type":"journal-article","created":{"date-parts":[[2016,5,27]],"date-time":"2016-05-27T21:03:13Z","timestamp":1464382993000},"page":"155-176","source":"Crossref","is-referenced-by-count":5,"title":["On the set\u2010theoretic strength of the existence of disjoint cofinal sets in posets without maximal elements"],"prefix":"10.1002","volume":"62","author":[{"given":"Paul","family":"Howard","sequence":"first","affiliation":[{"name":"Department of Mathematics Eastern Michigan University Ypsilanti MI 48197 United States of America"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Denis I.","family":"Saveliev","sequence":"additional","affiliation":[{"name":"Institute for Information Transmission Problems Russian Academy of Sciences 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Karetny 19 127994 Moscow Russian Federation"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eleftherios","family":"Tachtsis","sequence":"additional","affiliation":[{"name":"Department of Mathematics University of the Aegean Karlovassi 83200 Samos Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2016,5,27]]},"reference":[{"key":"e_1_2_7_2_1","doi-asserted-by":"publisher","DOI":"10.2307\/2273477"},{"issue":"4","key":"e_1_2_7_3_1","first-page":"329","article-title":"A model without ultrafilters","volume":"25","author":"Blass A.","year":"1977","journal-title":"Bull. Acad. Polon. S\u00e9r. Sci. Math. Astr. 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