Baumgartner's Axiom and Small Posets

Fuente: arXiv
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Main Authors: Marun, Pedro, Shelah, Saharon, Switzer, Corey Bacal
Format: Preprint
Published: 2025
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author Marun, Pedro
Shelah, Saharon
Switzer, Corey Bacal
author_facet Marun, Pedro
Shelah, Saharon
Switzer, Corey Bacal
contents We contribute to the study of $\aleph_1$-dense sets of reals, a mainstay in set theoretic research since Baumgartner's seminal work in the 70s. In particular, we show that it is consistent with $\textsf{MA}$ that there exists an $\aleph_1$-dense set of reals $A$ so that, in any cardinal-preserving generic extension by a forcing of size $\aleph_1$, $A$ and $A^*$ do not contain uncountable subsets which are order isomorphic. This strengthens a result of Avraham and the second author and yields a different proof of a theorem of Moore and Todorcevic.
format Preprint
id arxiv_https___arxiv_org_abs_2512_21247
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Baumgartner's Axiom and Small Posets
Marun, Pedro
Shelah, Saharon
Switzer, Corey Bacal
Logic
03E05, 03E35, 03E50
We contribute to the study of $\aleph_1$-dense sets of reals, a mainstay in set theoretic research since Baumgartner's seminal work in the 70s. In particular, we show that it is consistent with $\textsf{MA}$ that there exists an $\aleph_1$-dense set of reals $A$ so that, in any cardinal-preserving generic extension by a forcing of size $\aleph_1$, $A$ and $A^*$ do not contain uncountable subsets which are order isomorphic. This strengthens a result of Avraham and the second author and yields a different proof of a theorem of Moore and Todorcevic.
title Baumgartner's Axiom and Small Posets
topic Logic
03E05, 03E35, 03E50
url https://arxiv.org/abs/2512.21247