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We extend to singular cardinals the model-theoretical relation $\lambda \stackrel{\kappa}{\Rightarrow} \mu$ introduced in P. Lipparini, The compactness spectrum of abstract logics, large cardinals and combinatorial principles, Boll. Unione…

Logic · Mathematics 2008-05-13 Paolo Lipparini

Let M denote the ideal of first category subsets of R. We prove that min{card X: X \subseteq R, X \not\in M} is the smallest cardinality of a family S \subseteq {0,1}^\omega with the property that for each f: \omega -> \bigcup_{n \in…

Logic · Mathematics 2007-05-23 Apoloniusz Tyszka

For each countable ordinal $\alpha \ge 2$, the ideals $\mathsf{conv}_\alpha$ were introduced in ``Critical ideals for countable compact spaces'' (to appear in Fund. Math., see also arXiv:2503.12571) to characterize compact countable spaces…

Logic · Mathematics 2026-03-03 Malgorzata Kowalczuk

We provide analogues of the results from [FMR11, CMMR13] in the reference list (which correspond to the case $\kappa = \omega$) for arbitrary $\kappa$-Souslin quasi-orders on any Polish space, for $\kappa$ an infinite cardinal smaller than…

Logic · Mathematics 2019-03-19 Alessandro Andretta , Luca Motto Ros

This work is a part of my upcoming thesis [7]. We establish an equiconsistency between (1) weak indestructibility for all $\kappa +2$-degrees of strength for cardinals $\kappa $ in the presence of a proper class of strong cardinals, and (2)…

Logic · Mathematics 2024-11-20 James Holland

We give a development of the fine structure of mice with long extenders, to the level of $\kappa^+$-supercompact cardinals $\kappa$. We do this using a hierarchy with features more analogous to those familiar in the short extender context…

Logic · Mathematics 2025-06-12 Farmer Schlutzenberg

We study Structural Reflection beyond Vop\v{e}nka's Principle, at the level of almost-huge cardinals and higher, up to rank-into-rank embeddings. We identify and classify new large cardinal notions in that region that correspond to some…

Logic · Mathematics 2024-01-02 Joan Bagaria , Philipp Lücke

Generalizing Keisler's notion of regularity for ultrafilters, Taylor introduced degrees of regularity for ideals and showed that a countably complete nonregular ideal on $\omega_1$ must be somewhere $\omega_1$-dense. We prove a dichotomy…

Logic · Mathematics 2020-09-04 Monroe Eskew

For a discrete group $G$, we use the natural correspondence between ideals in the Boolean algebra $ \mathcal{P}_G$ of subsets of $G$ and closed subsets in the Stone-$\check{C}$ech compactifi-cation $\beta G$ as a right topological semigroup…

General Topology · Mathematics 2017-04-11 Igor Protasov , Ksenia Protasova

In this paper, we characterize the possible cofinalities of the least $\lambda$-strongly compact cardinal. We show that, on the one hand, for any regular cardinal, $\delta$, that carries a $\lambda$-complete uniform ultrafilter, it is…

Logic · Mathematics 2022-02-04 Zhixing You , Jiachen Yuan

This paper is devoted to studies of IwQN-spaces and some of their cardinal characteristics. Recently, \v{S}upina proved that I is not a weak P-ideal if and only if any topological space is an IQN-space. Moreover, under…

General Topology · Mathematics 2018-04-16 Adam Kwela

We extend prior results of Cody-Eskew, showing the consistency of GCH with the statement that for all regular cardinals $\kappa \leq \lambda$, where $\kappa$ is the successor of a regular cardinal, there is a rigid saturated ideal on…

Logic · Mathematics 2019-01-09 Monroe Eskew

We investigate forms of filter extension properties in the two-cardinal setting involving filters on $P_\kappa(\lambda)$. We generalize the filter games introduced by Holy and Schlicht in \cite{HolySchlicht:HierarchyRamseyLikeCardinals} to…

Logic · Mathematics 2026-02-20 Tom Benhamou , Victoria Gitman

We provide a model where u(\kappa) < 2^{\kappa} for a supercompact cardinal \kappa. Garti and Shelah have provided a sketch of how to obtain such a model by modifying the construction in a paper of Dzamonja and Shelah; we provide here a…

Logic · Mathematics 2015-11-10 A. D. Brooke-Taylor , V. Fischer , S. D. Friedman , D. C. Montoya

We characterize exactly the compactness properties of the product of \kappa\ copies of the space \omega\ with the discrete topology. The characterization involves uniform ultrafilters, infinitary languages, and the existence of nonstandard…

General Topology · Mathematics 2016-08-30 Paolo Lipparini

We prove that superclub implies $\mathfrak{s}=\aleph_1$. More generally, superclub at a successor of a weakly compact cardinal implies $\mathfrak{s}_\kappa=\kappa^+$. Based on this statement, we separate tiltan from superclub at a successor…

Logic · Mathematics 2025-05-28 Shimon Garti , Saharon Shelah

It is known that there are many notions of largeness in a semigroup that own rich combinatorial properties. In this paper, we focus on partition and almost disjoint properties of these notions. One of the most remarkable results with…

Combinatorics · Mathematics 2025-01-22 Teng Zhang

Answering questions raised in \cite{Leonetti, Uzcategui} we characterize ideals $\mathcal I\subseteq \mathcal P(\omega)$ such that $c_{0,\mathcal I}$ is complemented in $\ell_\infty$ as exactly those ideals for which the space $K_{\mathcal…

Functional Analysis · Mathematics 2025-12-02 Michael Hrušák , Luis Sáenz

Following \cite{bagaria2019large}, 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 $C\subseteq \kappa$…

Logic · Mathematics 2025-03-11 Douglas Blue , Grigor Sargsyan

We show that in the $\mathbb{P}_{\max}$ extension of a certain Chang-type model of determinacy, if $\kappa\in\{\omega_1, \omega_2, \omega_3\}$, then the restriction of the club filter on $\kappa\cap\mathrm{Cof}(\omega)$ to HOD is an…

Logic · Mathematics 2025-07-01 Navin Aksornthong , Takehiko Gappo , James Holland , Grigor Sargsyan