# Journal of the American Mathematical Society

Published by the American Mathematical Society, the Journal of the American Mathematical Society (JAMS) is devoted to research articles of the highest quality in all areas of mathematics.

ISSN 1088-6834 (online) ISSN 0894-0347 (print)

The 2020 MCQ for Journal of the American Mathematical Society is 4.83.

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## Ideals and strong axioms of determinacyHTML articles powered by AMS MathViewer

by Dominik Adolf, Grigor Sargsyan, Nam Trang, Trevor M. Wilson and Martin Zeman;
J. Amer. Math. Soc. 37 (2024), 1203-1273
DOI: https://doi.org/10.1090/jams/1041
Published electronically: January 26, 2024

## Abstract:

$\Theta$ is the least ordinal $\alpha$ with the property that there is no surjection $f:\mathbb {R}\rightarrow \alpha$. ${\mathsf {AD}}_{\mathbb {R}}$ is the Axiom of Determinacy for games played on the reals. It asserts that every game of length $\omega$ of perfect information in which players take turns to play reals is determined. An ideal $\mathcal {I}$ on $\omega _1$ is $\omega _1$-dense if the boolean algebra ${\wp }(\omega _1)/ \mathcal {I}$ has a dense subset of size $\omega _1$. We consider the theories, where $\mathsf {CH}$ stands for the Continuum Hypothesis, \begin{gather*} \mathsf {ZFC} + \mathsf {CH} + \text {“There is an $\omega _1$-dense ideal on $\omega _1$.''}\\ \mathsf {ZF}+{\mathsf {AD}}_{\mathbb {R}} + \text {“$\Theta$ is a regular cardinal.''}\end{gather*} The main result of this paper is that the first theory given above implies the existence of a class model of the second theory given above. Woodin, in unpublished work, showed that the consistency of the second equation given above implies the consistency of the first equation given above. We will also give a proof of this result, which, together with our main theorem, establish the equiconsistency of both the equations given above.

As a consequence, this resolves part of question 12 of W. Hugh Woodin [The axiom of determinacy, forcing axioms, and the nonstationary ideal, Walter de Gruyter & Co., Berlin, 1999], in particular, it shows that the theories (b) and (c) in question 12 of W. Hugh Woodin [The axiom of determinacy, forcing axioms, and the nonstationary ideal, Walter de Gruyter & Co., Berlin, 1999] are equiconsistent. Thus, our work completes the work that was started by Woodin and Ketchersid in [Toward AD($\mathbb {R}$) from the continuum hypothesis and an $\omega _1$-dense ideal, ProQuest LLC, Ann Arbor, MI, 2000] some 25 years ago. We also establish other theorems of similar nature in this paper, showing the equiconsistency of the second equation given above and the statement that the non-stationary ideal on ${\wp }_{\omega _1}(\mathbb {R})$ is strong and pseudo-homogeneous. The aforementioned results are the only known equiconsistency results at the level of $\mathsf {AD}_{\mathbb {R}} + \text {“$Θ$is a regular cardinal.''}$

References
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Bibliographic Information
• Affiliation: Department of Mathematics, University of North Texas, 1155 Union Circle #311430, Denton, Texas 76203-5017, USA
• MR Author ID: 1243413
• Grigor Sargsyan
• Affiliation: Institute of Mathematics of the Polish Academy of Sciences, Antoniego Abrahama 18 81-825 Sopot, Poland
• MR Author ID: 677243
• ORCID: 0000-0002-6095-1997
• Email: gsargsyan@impan.pl
• Nam Trang
• Affiliation: Department of Mathematics, University of North Texas, 1155 Union Circle #311430, Denton, Texas 76203-5017, USA
• MR Author ID: 1067824
• ORCID: 0000-0002-7528-682X
• Email: Nam.Trang@unt.edu
• Trevor M. Wilson
• Affiliation: Department of Mathematics, Miami University, 123 Bachelor Hall, 301 S. Patterson Ave., Oxford, OH 45056, USA
• MR Author ID: 766093
• ORCID: 0000-0001-9513-3612
• Email: twilson@miamioh.edu
• Martin Zeman
• Affiliation: Department of Mathematics, University of California Irvine, Irvine, CA 92697-3875, USA
• MR Author ID: 609638
• Email: mzeman@math.uci.edu
• Received by editor(s): September 20, 2022
• Received by editor(s) in revised form: September 22, 2023
• Published electronically: January 26, 2024
• Additional Notes: The second author was supported by NCN via NCN Grant WEAVE-UNISONO Id 567137. The third author was supported by the NSF via Career Award DMS-1945592.