{"title":"你能把科姆亚特无法进入的地方带走吗?","authors":"Hossein Lamei Ramandi , Stevo Todorcevic","doi":"10.1016/j.apal.2024.103452","DOIUrl":null,"url":null,"abstract":"<div><p>In this paper we aim to compare Kurepa trees and Aronszajn trees. Moreover, we analyze the effect of large cardinal assumptions on this comparison. Using the method of walks on ordinals, we will show it is consistent with ZFC that there is a Kurepa tree and every Kurepa tree contains an Aronszajn subtree, if there is an inaccessible cardinal. This is stronger than Komjath's theorem in <span>[5]</span>, where he proves the same consistency from two inaccessible cardinals. Moreover, we prove it is consistent with ZFC that there is a Kurepa tree <em>T</em> such that if <span><math><mi>U</mi><mo>⊂</mo><mi>T</mi></math></span> is a Kurepa tree with the inherited order from <em>T</em>, then <em>U</em> has an Aronszajn subtree. This theorem uses no large cardinal assumption. Our last theorem immediately implies the following: If <span><math><msub><mrow><mi>MA</mi></mrow><mrow><msub><mrow><mi>ω</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></msub></math></span> holds and <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> is not a Mahlo cardinal in <figure><img></figure> then there is a Kurepa tree with the property that every Kurepa subset has an Aronszajn subtree. Our work entails proving a new lemma about Todorcevic's <em>ρ</em> function which might be useful in other contexts.</p></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"175 7","pages":"Article 103452"},"PeriodicalIF":0.6000,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168007224000502/pdfft?md5=1993a5c4769b9c98665f24c8f3058ad9&pid=1-s2.0-S0168007224000502-main.pdf","citationCount":"0","resultStr":"{\"title\":\"Can you take Komjath's inaccessible away?\",\"authors\":\"Hossein Lamei Ramandi , Stevo Todorcevic\",\"doi\":\"10.1016/j.apal.2024.103452\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>In this paper we aim to compare Kurepa trees and Aronszajn trees. Moreover, we analyze the effect of large cardinal assumptions on this comparison. Using the method of walks on ordinals, we will show it is consistent with ZFC that there is a Kurepa tree and every Kurepa tree contains an Aronszajn subtree, if there is an inaccessible cardinal. This is stronger than Komjath's theorem in <span>[5]</span>, where he proves the same consistency from two inaccessible cardinals. Moreover, we prove it is consistent with ZFC that there is a Kurepa tree <em>T</em> such that if <span><math><mi>U</mi><mo>⊂</mo><mi>T</mi></math></span> is a Kurepa tree with the inherited order from <em>T</em>, then <em>U</em> has an Aronszajn subtree. This theorem uses no large cardinal assumption. Our last theorem immediately implies the following: If <span><math><msub><mrow><mi>MA</mi></mrow><mrow><msub><mrow><mi>ω</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></msub></math></span> holds and <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> is not a Mahlo cardinal in <figure><img></figure> then there is a Kurepa tree with the property that every Kurepa subset has an Aronszajn subtree. Our work entails proving a new lemma about Todorcevic's <em>ρ</em> function which might be useful in other contexts.</p></div>\",\"PeriodicalId\":50762,\"journal\":{\"name\":\"Annals of Pure and Applied Logic\",\"volume\":\"175 7\",\"pages\":\"Article 103452\"},\"PeriodicalIF\":0.6000,\"publicationDate\":\"2024-04-15\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.sciencedirect.com/science/article/pii/S0168007224000502/pdfft?md5=1993a5c4769b9c98665f24c8f3058ad9&pid=1-s2.0-S0168007224000502-main.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Annals of Pure and Applied Logic\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0168007224000502\",\"RegionNum\":2,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"LOGIC\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Annals of Pure and Applied Logic","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0168007224000502","RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"LOGIC","Score":null,"Total":0}
In this paper we aim to compare Kurepa trees and Aronszajn trees. Moreover, we analyze the effect of large cardinal assumptions on this comparison. Using the method of walks on ordinals, we will show it is consistent with ZFC that there is a Kurepa tree and every Kurepa tree contains an Aronszajn subtree, if there is an inaccessible cardinal. This is stronger than Komjath's theorem in [5], where he proves the same consistency from two inaccessible cardinals. Moreover, we prove it is consistent with ZFC that there is a Kurepa tree T such that if is a Kurepa tree with the inherited order from T, then U has an Aronszajn subtree. This theorem uses no large cardinal assumption. Our last theorem immediately implies the following: If holds and is not a Mahlo cardinal in then there is a Kurepa tree with the property that every Kurepa subset has an Aronszajn subtree. Our work entails proving a new lemma about Todorcevic's ρ function which might be useful in other contexts.
期刊介绍:
The journal Annals of Pure and Applied Logic publishes high quality papers in all areas of mathematical logic as well as applications of logic in mathematics, in theoretical computer science and in other related disciplines. All submissions to the journal should be mathematically correct, well written (preferably in English)and contain relevant new results that are of significant interest to a substantial number of logicians. The journal also considers submissions that are somewhat too long to be published by other journals while being too short to form a separate memoir provided that they are of particular outstanding quality and broad interest. In addition, Annals of Pure and Applied Logic occasionally publishes special issues of selected papers from well-chosen conferences in pure and applied logic.