JOURNAL ARTICLE
More definable combinatorics around the first and second uncountable cardinals.
Published In: Journal of Mathematical Logic, 2023, v. 23, n. 3. P. 1 1 of 3
Database: Academic Search Ultimate 2 of 3
Authored By: Chan, William; Jackson, Stephen; Trang, Nam 3 of 3
Abstract
Assume Z F + A D. If is an ordinal and X is a set of ordinals, then [ X ] ∗ is the collection of order-preserving functions f : → X which have uniform cofinality ω and discontinuous everywhere. The weak partition properties on ω 1 and ω 2 yield partition measures on [ ω 1 ] ∗ when < ω 1 and [ ω 2 ] ∗ when < ω 2 . The following almost everywhere continuity properties for functions on partition spaces with respect to these partition measures will be shown. For every < ω 1 and function Φ : [ ω 1 ] → ω 1 , there is a club C ⊆ ω 1 and a ζ < so that for all f , g ∈ [ C ] ∗ , if f ↾ ζ = g ↾ ζ and sup (f) = sup (g) , then Φ (f) = Φ (g). For every < ω 2 and function Φ : [ ω 2 ] → ω 2 , there is an ω -club C ⊆ ω 2 and a ζ < so that for all f , g ∈ [ C ] ∗ , if f ↾ ζ = g ↾ ζ and sup (f) = sup (g) , then Φ (f) = Φ (g). The previous two continuity results will be used to distinguish the cardinalities of some important subsets of (ω 2) : | [ ω 1 ] ω | < | [ ω 1 ] < ω 1 |. | [ ω 2 ] ω | < | [ ω 2 ] < ω 1 | < | [ ω 2 ] ω 1 | < | [ ω 2 ] < ω 2 |. ¬ (| [ ω 1 ] < ω 1 | ≤ | [ ω 2 ] ω |). ¬ (| [ ω 1 ] ω 1 | ≤ | [ ω 2 ] < ω 1 |). It will also be shown that [ ω 1 ] ω has the Jónsson property: For every Φ : < ω ([ ω 1 ] ω) → [ ω 1 ] ω , there is an X ⊆ [ ω 1 ] ω with | X | = | [ ω 1 ] ω | so that Φ [ < ω X ] ≠ [ ω 1 ] ω . [ABSTRACT FROM AUTHOR]
Additional Information
- Source:Journal of Mathematical Logic. 2023/12, Vol. 23, Issue 3, p1
- Document Type:Article
- Subject Area:Mathematics
- Publication Date:2023
- ISSN:0219-0613
- DOI:10.1142/S0219061322500295
- Accession Number:164395570
- Copyright Statement:Copyright of Journal of Mathematical Logic is the property of World Scientific Publishing Company and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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