Pub Date : 2025-05-05DOI: 10.1016/j.apal.2025.103607
Arturo Martínez-Celis, Tomasz Żuchowski
Given a function , a set is free for f if is finite. For a class of functions , we define as the smallest size of a family such that for every there is a set which is free for f, and as the smallest size of a family such that for every there is such that A is not free for f. We compare several versions of these cardinal invariants with some of the classical cardinal characteristics of the continuum. Using these notions, we partially answer some questions from [20] and [2].
{"title":"On cardinal invariants related to Rosenthal families and large-scale topology","authors":"Arturo Martínez-Celis, Tomasz Żuchowski","doi":"10.1016/j.apal.2025.103607","DOIUrl":"10.1016/j.apal.2025.103607","url":null,"abstract":"<div><div>Given a function <span><math><mi>f</mi><mo>∈</mo><msup><mrow><mi>ω</mi></mrow><mrow><mi>ω</mi></mrow></msup></math></span>, a set <span><math><mi>A</mi><mo>∈</mo><msup><mrow><mo>[</mo><mi>ω</mi><mo>]</mo></mrow><mrow><mi>ω</mi></mrow></msup></math></span> is <em>free for f</em> if <span><math><mi>f</mi><mo>[</mo><mi>A</mi><mo>]</mo><mo>∩</mo><mi>A</mi></math></span> is finite. For a class of functions <span><math><mi>Γ</mi><mo>⊆</mo><msup><mrow><mi>ω</mi></mrow><mrow><mi>ω</mi></mrow></msup></math></span>, we define <span><math><msub><mrow><mi>ros</mi></mrow><mrow><mi>Γ</mi></mrow></msub></math></span> as the smallest size of a family <span><math><mi>A</mi><mo>⊆</mo><msup><mrow><mo>[</mo><mi>ω</mi><mo>]</mo></mrow><mrow><mi>ω</mi></mrow></msup></math></span> such that for every <span><math><mi>f</mi><mo>∈</mo><mi>Γ</mi></math></span> there is a set <span><math><mi>A</mi><mo>∈</mo><mi>A</mi></math></span> which is free for <em>f</em>, and <span><math><msub><mrow><mi>Δ</mi></mrow><mrow><mi>Γ</mi></mrow></msub></math></span> as the smallest size of a family <span><math><mi>F</mi><mo>⊆</mo><mi>Γ</mi></math></span> such that for every <span><math><mi>A</mi><mo>∈</mo><msup><mrow><mo>[</mo><mi>ω</mi><mo>]</mo></mrow><mrow><mi>ω</mi></mrow></msup></math></span> there is <span><math><mi>f</mi><mo>∈</mo><mi>F</mi></math></span> such that <em>A</em> is not free for <em>f</em>. We compare several versions of these cardinal invariants with some of the classical cardinal characteristics of the continuum. Using these notions, we partially answer some questions from <span><span>[20]</span></span> and <span><span>[2]</span></span>.</div></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"176 8","pages":"Article 103607"},"PeriodicalIF":0.6,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143922505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-05DOI: 10.1016/j.apal.2025.103606
Vera Fischer , Sy David Friedman , David Schrittesser , Asger Törnquist
We develop a new forcing notion for adjoining self-coding cofinitary permutations and use it to show that consistently, the minimal cardinality of a maximal cofinitary group (MCG) is strictly between and , and there is a -definable MCG of this cardinality. Here is optimal, making this result a natural counterpart to the Borel MCG of Horowitz and Shelah. Our theorem has its analogue in the realm of maximal almost disjoint (MAD) families, extending a line of results regarding the definability properties of MAD families in models with large continuum.
{"title":"Good projective witnesses","authors":"Vera Fischer , Sy David Friedman , David Schrittesser , Asger Törnquist","doi":"10.1016/j.apal.2025.103606","DOIUrl":"10.1016/j.apal.2025.103606","url":null,"abstract":"<div><div>We develop a new forcing notion for adjoining self-coding cofinitary permutations and use it to show that consistently, the minimal cardinality <span><math><msub><mrow><mi>a</mi></mrow><mrow><mtext>g</mtext></mrow></msub></math></span> of a maximal cofinitary group (MCG) is strictly between <span><math><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> and <span><math><mi>c</mi></math></span>, and there is a <span><math><msubsup><mrow><mi>Π</mi></mrow><mrow><mn>2</mn></mrow><mrow><mn>1</mn></mrow></msubsup></math></span>-definable MCG of this cardinality. Here <span><math><msubsup><mrow><mi>Π</mi></mrow><mrow><mn>2</mn></mrow><mrow><mn>1</mn></mrow></msubsup></math></span> is optimal, making this result a natural counterpart to the Borel MCG of Horowitz and Shelah. Our theorem has its analogue in the realm of maximal almost disjoint (MAD) families, extending a line of results regarding the definability properties of MAD families in models with large continuum.</div></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"176 8","pages":"Article 103606"},"PeriodicalIF":0.6,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143927371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-02DOI: 10.1016/j.apal.2025.103605
Slavko Moconja , Predrag Tanović
We introduce and study weak o-minimality in the context of complete types in an arbitrary first-order theory. A type is weakly o-minimal if for some relatively A-definable linear order, <, on every relatively -definable subset of has finitely many convex components in . We establish many nice properties of weakly o-minimal types. For example, we prove that weakly o-minimal types are dp-minimal and share several properties of weight-one types in stable theories, and that a version of monotonicity theorem holds for relatively definable functions on the locus of a weakly o-minimal type.
{"title":"Weakly o-minimal types","authors":"Slavko Moconja , Predrag Tanović","doi":"10.1016/j.apal.2025.103605","DOIUrl":"10.1016/j.apal.2025.103605","url":null,"abstract":"<div><div>We introduce and study weak o-minimality in the context of complete types in an arbitrary first-order theory. A type <span><math><mi>p</mi><mo>∈</mo><mi>S</mi><mo>(</mo><mi>A</mi><mo>)</mo></math></span> is weakly o-minimal if for some relatively <em>A</em>-definable linear order, <, on <span><math><mi>p</mi><mo>(</mo><mi>C</mi><mo>)</mo></math></span> every relatively <span><math><msub><mrow><mi>L</mi></mrow><mrow><mi>C</mi></mrow></msub></math></span>-definable subset of <span><math><mi>p</mi><mo>(</mo><mi>C</mi><mo>)</mo></math></span> has finitely many convex components in <span><math><mo>(</mo><mi>p</mi><mo>(</mo><mi>C</mi><mo>)</mo><mo>,</mo><mo><</mo><mo>)</mo></math></span>. We establish many nice properties of weakly o-minimal types. For example, we prove that weakly o-minimal types are dp-minimal and share several properties of weight-one types in stable theories, and that a version of monotonicity theorem holds for relatively definable functions on the locus of a weakly o-minimal type.</div></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"176 9","pages":"Article 103605"},"PeriodicalIF":0.6,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143922216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-23DOI: 10.1016/j.apal.2025.103604
Derek Levinson
We find bounds for the maximal length of a sequence of distinct -sets under AD and show there is no sequence of distinct -sets of length . As a special case, there is no sequence of distinct -sets of length . These are the optimal results for the pointclasses and .
{"title":"Unreachability of Γ2n+1,m","authors":"Derek Levinson","doi":"10.1016/j.apal.2025.103604","DOIUrl":"10.1016/j.apal.2025.103604","url":null,"abstract":"<div><div>We find bounds for the maximal length of a sequence of distinct <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mn>2n</mn><mo>+</mo><mn>1</mn><mo>,</mo><mi>m</mi></mrow></msub></math></span>-sets under <em>AD</em> and show there is no sequence of distinct <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mn>2n</mn><mo>+</mo><mn>1</mn></mrow></msub></math></span>-sets of length <span><math><msubsup><mrow><mi>δ</mi></mrow><mrow><mn>2n</mn><mo>+</mo><mn>3</mn></mrow><mrow><mn>1</mn></mrow></msubsup></math></span>. As a special case, there is no sequence of distinct <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mn>1</mn><mo>,</mo><mi>m</mi></mrow></msub></math></span>-sets of length <span><math><msub><mrow><mi>ℵ</mi></mrow><mrow><mi>m</mi><mo>+</mo><mn>2</mn></mrow></msub></math></span>. These are the optimal results for the pointclasses <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mn>2n</mn><mo>+</mo><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mn>1</mn><mo>,</mo><mi>m</mi></mrow></msub></math></span>.</div></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"176 9","pages":"Article 103604"},"PeriodicalIF":0.6,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143895035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-22DOI: 10.1016/j.apal.2025.103603
Eleftherios Tachtsis
<div><div>We <em>answer open questions</em> from Keremedis (2016) <span><span>[12]</span></span> and Keremedis and Tachtsis (2022) <span><span>[16]</span></span>, and <em>properly strengthen some results</em> from the above papers as well as from Keremedis et al. (2023) <span><span>[19]</span></span>. In particular, and among other results, we establish the following:<ul><li><span>1.</span><span><div>The Boolean Prime Ideal Theorem does not imply “For every sequentially compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span>, <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≤</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” in <strong>ZF</strong> (Zermelo–Fraenkel set theory without the Axiom of Choice (<strong>AC</strong>)).</div></span></li><li><span>2.</span><span><div>“Every linearly ordered set can be well ordered” ∧ “The union of a well-orderable family of well-orderable sets is well orderable” ∧ “For every uncountable sequentially compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span>, <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>=</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” does not imply the Axiom of Countable Choice in <strong>ZFA</strong> (<strong>ZF</strong> with atoms).</div></span></li><li><span>3.</span><span><div>“For every uncountable compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span>, <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≥</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” does not imply “For every uncountable sequentially compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span>, <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≥</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” in <strong>ZFA</strong>”.</div></span></li><li><span>4.</span><span><div>“For every uncountable sequentially compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span> <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≥</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” does not imply “For every uncountable compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span>, <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>=</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” in <strong>ZFA</strong>.</div></span></li><li><span>5.</span><span><div>“For every uncountable sequentially compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>
我们回答了Keremedis(2016)[12]和Keremedis and Tachtsis(2022)[19]的开放性问题,并适当加强了上述论文以及Keremedis等人(2023)[19]的一些结果。特别地,在其他结果中,我们确立了以下几点:在ZF (Zermelo-Fraenkel集合论,无选择公理(AC)).2中,布尔素数理想定理并不意味着“对于每一个序紧度量空间< X,d >, |X|≤2¹0”。“每个线性有序集都可以良序”∧良序集族的并是良序的“∧”对于每一个不可数序紧度量空间< X,d >, |X|=2¹0”并不意味着ZFA(含原子的ZF)中的可数选择公理。“对于每一个不可数紧度量空间< X,d >, |X|≥2¹0”并不意味着在ZFA中“对于每一个不可数连续紧度量空间< X,d >, |X|≥2¹0”。ZFA.5中的“对于每一个不可数连续紧度量空间< X,d > |X|≥2¹0”并不意味着“对于每一个不可数紧度量空间< X,d >, |X|=2¹0”。“对于每一个不可数序紧度量空间< X,d > |X|≥2 ^ 0”并不蕴涵ZFA.6中可数集的可数选择公理(CMCω)。“每一个线性有序的集合都是良序的”并不意味着ZFA中的“有限集合的可数选择公理”∨“每一个无限紧度量空间都有一个无限分散的子空间”。我们还讨论了斯通定理“每个度量空间都是准紧的”(ST)的演绎强度的开放问题,并提供了ST是否意味着CMCω的非平凡部分答案。特别地,我们证明了形式上较弱的命题“对于每一个度量空间< X,d >, |X|≥2 ^ 0或< X,d >是准紧的”并不意味着在ZFA中有CMCω。我们还证明,对于每一个不可数正则基数κ,在ZF中的“for all infinite良序基数λ<;κ, the Principle of Dependent Choices for λ成立”并不隐含上述ST的弱形式。
{"title":"Metric spaces in choiceless set theory","authors":"Eleftherios Tachtsis","doi":"10.1016/j.apal.2025.103603","DOIUrl":"10.1016/j.apal.2025.103603","url":null,"abstract":"<div><div>We <em>answer open questions</em> from Keremedis (2016) <span><span>[12]</span></span> and Keremedis and Tachtsis (2022) <span><span>[16]</span></span>, and <em>properly strengthen some results</em> from the above papers as well as from Keremedis et al. (2023) <span><span>[19]</span></span>. In particular, and among other results, we establish the following:<ul><li><span>1.</span><span><div>The Boolean Prime Ideal Theorem does not imply “For every sequentially compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span>, <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≤</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” in <strong>ZF</strong> (Zermelo–Fraenkel set theory without the Axiom of Choice (<strong>AC</strong>)).</div></span></li><li><span>2.</span><span><div>“Every linearly ordered set can be well ordered” ∧ “The union of a well-orderable family of well-orderable sets is well orderable” ∧ “For every uncountable sequentially compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span>, <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>=</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” does not imply the Axiom of Countable Choice in <strong>ZFA</strong> (<strong>ZF</strong> with atoms).</div></span></li><li><span>3.</span><span><div>“For every uncountable compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span>, <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≥</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” does not imply “For every uncountable sequentially compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span>, <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≥</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” in <strong>ZFA</strong>”.</div></span></li><li><span>4.</span><span><div>“For every uncountable sequentially compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span> <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>≥</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” does not imply “For every uncountable compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>〉</mo></math></span>, <span><math><mo>|</mo><mi>X</mi><mo>|</mo><mo>=</mo><msup><mrow><mn>2</mn></mrow><mrow><msub><mrow><mi>ℵ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msup></math></span>” in <strong>ZFA</strong>.</div></span></li><li><span>5.</span><span><div>“For every uncountable sequentially compact metric space <span><math><mo>〈</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"176 9","pages":"Article 103603"},"PeriodicalIF":0.6,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143886674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-08DOI: 10.1016/j.apal.2025.103601
Arturo Rodríguez Fanlo , Ori Segel
We develop the basic model theory of local positive logic, a new logic that mixes positive logic (where negation is not allowed) and local logic (where models omit types of infinite distant pairs). We study several basic model theoretic notions such as compactness, positive closedness (existential closedness) and completeness (irreducibility).
{"title":"Completeness in local positive logic","authors":"Arturo Rodríguez Fanlo , Ori Segel","doi":"10.1016/j.apal.2025.103601","DOIUrl":"10.1016/j.apal.2025.103601","url":null,"abstract":"<div><div>We develop the basic model theory of local positive logic, a new logic that mixes positive logic (where negation is not allowed) and local logic (where models omit types of infinite distant pairs). We study several basic model theoretic notions such as compactness, positive closedness (existential closedness) and completeness (irreducibility).</div></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"176 7","pages":"Article 103601"},"PeriodicalIF":0.6,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-07DOI: 10.1016/j.apal.2025.103602
Taras Banakh , Robert Rałowski , Szymon Żeberski
Using a game-theoretic approach we present a generalization of the classical result of Brzuchowski, Cichoń, Grzegorek and Ryll-Nardzewski on non-measurable unions. We also present applications of obtained results to Marczewski–Burstin representable ideals.
{"title":"The Set-Cover game and non-measurable unions","authors":"Taras Banakh , Robert Rałowski , Szymon Żeberski","doi":"10.1016/j.apal.2025.103602","DOIUrl":"10.1016/j.apal.2025.103602","url":null,"abstract":"<div><div>Using a game-theoretic approach we present a generalization of the classical result of Brzuchowski, Cichoń, Grzegorek and Ryll-Nardzewski on non-measurable unions. We also present applications of obtained results to Marczewski–Burstin representable ideals.</div></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"176 8","pages":"Article 103602"},"PeriodicalIF":0.6,"publicationDate":"2025-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-04DOI: 10.1016/j.apal.2025.103586
Liang Yu
We prove that, assuming ZF, and restricted to any -pointed set, Chaitin's is not injective for any universal prefix-free Turing machine U, and that fails to be degree invariant in a very strong sense, answering several recent questions in descriptive set theory. Moreover, we show that under , every function f mapping x to x-random must be uncountable-to-one over an upper cone of Turing degrees.
我们证明,假设 ZF,并限制于任何 ≤T 点集,柴廷的ΩU:x↦ΩUx=∑Ux(σ)↓2-|σ| 对于任何通用无前缀图灵机 U 都不是注入式的,并且ΩUx 在非常强的意义上不具有度不变性,这回答了描述集合论中最近的几个问题。此外,我们还证明了在 ZF+AD 下,映射 x 到 x-random 的每个函数 f 都必须在图灵度的上锥上是不可数到一的。
{"title":"Some more results on relativized Chaitin's Ω","authors":"Liang Yu","doi":"10.1016/j.apal.2025.103586","DOIUrl":"10.1016/j.apal.2025.103586","url":null,"abstract":"<div><div>We prove that, assuming ZF, and restricted to any <span><math><msub><mrow><mo>≤</mo></mrow><mrow><mi>T</mi></mrow></msub></math></span>-pointed set, Chaitin's <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>U</mi></mrow></msub><mo>:</mo><mi>x</mi><mo>↦</mo><msubsup><mrow><mi>Ω</mi></mrow><mrow><mi>U</mi></mrow><mrow><mi>x</mi></mrow></msubsup><mo>=</mo><msub><mrow><mo>∑</mo></mrow><mrow><msup><mrow><mi>U</mi></mrow><mrow><mi>x</mi></mrow></msup><mo>(</mo><mi>σ</mi><mo>)</mo><mo>↓</mo></mrow></msub><msup><mrow><mn>2</mn></mrow><mrow><mo>−</mo><mo>|</mo><mi>σ</mi><mo>|</mo></mrow></msup></math></span> is not injective for any universal prefix-free Turing machine <em>U</em>, and that <span><math><msubsup><mrow><mi>Ω</mi></mrow><mrow><mi>U</mi></mrow><mrow><mi>x</mi></mrow></msubsup></math></span> fails to be degree invariant in a very strong sense, answering several recent questions in descriptive set theory. Moreover, we show that under <span><math><mrow><mi>ZF</mi></mrow><mo>+</mo><mrow><mi>AD</mi></mrow></math></span>, every function <em>f</em> mapping <em>x</em> to <em>x</em>-random must be uncountable-to-one over an upper cone of Turing degrees.</div></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"176 8","pages":"Article 103586"},"PeriodicalIF":0.6,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143816774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-25DOI: 10.1016/j.apal.2025.103585
M. Drzewiecka , A. Ivanov , B. Mokry
Let and be the closure of the conjugacy class of ρ in . We show that contains a conjugacy class, say C, which is comeagre in . We describe representatives of C. Furthermore, we show that the family of finite partial maps extendable to elements of C has the cofinal amalgamation property.
{"title":"Generics in invariant subsets of the group of order preserving permutations of Q","authors":"M. Drzewiecka , A. Ivanov , B. Mokry","doi":"10.1016/j.apal.2025.103585","DOIUrl":"10.1016/j.apal.2025.103585","url":null,"abstract":"<div><div>Let <span><math><mi>ρ</mi><mo>∈</mo><mrow><mi>Aut</mi></mrow><mo>(</mo><mi>Q</mi><mo>,</mo><mo><</mo><mo>)</mo></math></span> and <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>ρ</mi></mrow></msub></math></span> be the closure of the conjugacy class of <em>ρ</em> in <span><math><mrow><mi>Aut</mi></mrow><mo>(</mo><mi>Q</mi><mo>,</mo><mo><</mo><mo>)</mo></math></span>. We show that <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>ρ</mi></mrow></msub></math></span> contains a conjugacy class, say <em>C</em>, which is comeagre in <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>ρ</mi></mrow></msub></math></span>. We describe representatives of <em>C</em>. Furthermore, we show that the family of finite partial maps extendable to elements of <em>C</em> has the cofinal amalgamation property.</div></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"176 8","pages":"Article 103585"},"PeriodicalIF":0.6,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143799916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-21DOI: 10.1016/j.apal.2025.103584
Moti Gitik , Sittinon Jirattikansakul
Continuing [1], we develop a version of Extender-based Magidor-Radin forcing where there are no extenders on the top ordinal. As an application, we provide another approach to obtain a failure of SCH on a club subset of an inaccessible cardinal, and a model where the cardinal arithmetic behaviors are different on stationary classes, whose union is the club, is provided. The cardinals and the cofinalities outside the clubs are not affected by the forcings.
{"title":"Extender-based Magidor-Radin forcings without top extenders","authors":"Moti Gitik , Sittinon Jirattikansakul","doi":"10.1016/j.apal.2025.103584","DOIUrl":"10.1016/j.apal.2025.103584","url":null,"abstract":"<div><div>Continuing <span><span>[1]</span></span>, we develop a version of Extender-based Magidor-Radin forcing where there are no extenders on the top ordinal. As an application, we provide another approach to obtain a failure of SCH on a club subset of an inaccessible cardinal, and a model where the cardinal arithmetic behaviors are different on stationary classes, whose union is the club, is provided. The cardinals and the cofinalities outside the clubs are not affected by the forcings.</div></div>","PeriodicalId":50762,"journal":{"name":"Annals of Pure and Applied Logic","volume":"176 8","pages":"Article 103584"},"PeriodicalIF":0.6,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143760627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}