$\textsf {AD}^{+}$ implies $ \omega _{1}$ is a club $ \Theta $-Berkeley cardinal

Abstract Following [1], given cardinals $\kappa <\lambda $ , we say $\kappa $ is a club $\lambda $ -Berkeley cardinal if for every transitive set N of size $<\lambda $ such that $\kappa \subseteq N$ , there is a club $C\subseteq \kappa $ with the property that for every $\eta \in C$ , there is an elementary embedding $j: N\rightarrow N$ with $\mathrm {crit }(j)=\eta $ . We say $\kappa $ is $\nu $ -club $\lambda $ -Berkeley if $C\subseteq \kappa $ as above is a $\nu $ -club. We say $\kappa $ is $\lambda $ -Berkeley if C is unbounded in $\kappa $ . We show that under $\textsf {AD}^{+}$ , (1) every regular Suslin cardinal is $\omega $ -club $\Theta $ -Berkeley (see Theorem 7.1), (2) $\omega _1$ is club $\Theta $ -Berkeley (see Theorem 3.1 and Theorem 7.1), and (3) the ’s are $\Theta $ -Berkeley – in particular, $\omega _2$ is $\Theta $ -Berkeley (see Remark 7.5). Along the way, we represent regular Suslin cardinals in direct limits as cutpoint cardinals (see Theorem 5.1). This topic has been studied in [31] and [4], albeit from a different point of view. We also show that, assuming $V=L({\mathbb {R}})+{\textsf {AD}}$ , $\omega _1$ is not $\Theta ^+$ -Berkeley, so the result stated in the title is optimal (see Theorem 9.14 and Theorem 9.19).

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Publication Details

Journal
Forum of Mathematics Sigma
Published
2025-01-01
DOI
https://doi.org/10.1017/fms.2025.10082
Citations
1
Primary Topic
Advanced Topology and Set Theory
Type
article
Field-Weighted Citation Impact
4.09

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article

$\textsf {AD}^{+}$ implies $ \omega _{1}$ is a club $ \Theta $-Berkeley cardinal

Grigor Sargsyan, Douglas Blue
1 citations
Forum of Mathematics Sigma
Advanced Topology and Set Theory
4.09
article

$\textsf {AD}^{+}$ implies $ \omega _{1}$ is a club $ \Theta $-Berkeley cardinal

Grigor Sargsyan, Douglas Blue
article en
1 citations

Abstract

Abstract Following [1], given cardinals $\kappa <\lambda $ , we say $\kappa $ is a club $\lambda $ -Berkeley cardinal if for every transitive set N of size $<\lambda $ such that $\kappa \subseteq N$ , there is a club $C\subseteq \kappa $ with the property that for every $\eta \in C$ , there is an elementary embedding $j: N\rightarrow N$ with $\mathrm {crit }(j)=\eta $ . We say $\kappa $ is $\nu $ -club $\lambda $ -Berkeley if $C\subseteq \kappa $ as above is a $\nu $ -club. We say $\kappa $ is $\lambda $ -Berkeley if C is unbounded in $\kappa $ . We show that under $\textsf {AD}^{+}$ , (1) every regular Suslin cardinal is $\omega $ -club $\Theta $ -Berkeley (see Theorem 7.1), (2) $\omega _1$ is club $\Theta $ -Berkeley (see Theorem 3.1 and Theorem 7.1), and (3) the ’s are $\Theta $ -Berkeley – in particular, $\omega _2$ is $\Theta $ -Berkeley (see Remark 7.5). Along the way, we represent regular Suslin cardinals in direct limits as cutpoint cardinals (see Theorem 5.1). This topic has been studied in [31] and [4], albeit from a different point of view. We also show that, assuming $V=L({\mathbb {R}})+{\textsf {AD}}$ , $\omega _1$ is not $\Theta ^+$ -Berkeley, so the result stated in the title is optimal (see Theorem 9.14 and Theorem 9.19).

Forum of Mathematics SigmaVol. 13
University of Pittsburgh (US), Polish Academy of Sciences (PL)
Narodowe Centrum Nauki
Openalex Percentile: Top 8%
Advanced Topology and Set Theory
4.09
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$\textsf {AD}^{+}$ implies $ \omega _{1}$ is a club $ \Theta $-Berkeley cardinal — Grigor Sargsyan, Douglas Blue · Forum of Mathematics Sigma (2025) | TGRS Research Map | TGRS