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A ccc-generically supercompact cardinal $\kappa$ can be smaller than or equal to the continuum. On the other hand, such a cardinal $\kappa$ still satisfies diverse largeness properties, like that it is a stationary limit of ccc-generically…

Logic · Mathematics 2022-02-17 Sakaé Fuchino , Hiroshi Sakai

We demonstrate that the technology of Radin forcing can be used to transfer compactness properties at a weakly inaccessible but not strong limit cardinal to a strongly inaccessible cardinal. As an application, relative to the existence of…

Logic · Mathematics 2024-04-29 Tom Benhamou , Jing Zhang

We continue the study from \cite{BrendleFreidmanMontoya, vandervlugtlocalizationcardinals} of localization cardinals $\mfb_\kappa(\in^*)$ and $\mfd_\kappa(\in^*)$ and their variants at regular uncountable $\kappa$. We prove that if $\kappa$…

Logic · Mathematics 2025-11-11 Tom Benhamou , Corey Bacal Switzer

Let kappa be an uncountable regular cardinal. Assuming 2^kappa=kappa^+, we show that the clone lattice on a set of size kappa is not dually atomic.

Rings and Algebras · Mathematics 2007-06-11 Martin Goldstern , Saharon Shelah

We investigate the behavior of cardinal characteristics of the reals under extensions that do not add new ${<}\kappa$-sequences (for some regular $\kappa$). As an application, we show that consistently the following cardinal characteristics…

Logic · Mathematics 2021-05-18 Martin Goldstern , Jakob Kellner , Diego A. Mejía , Saharon Shelah

We produce, relative to a ${\sf ZFC}$ model with a supercompact cardinal, a ${\sf ZFC}$ model of the Proper Forcing Axiom in which the nonstationary ideal on $\omega_1$ is $\Pi_1$-definable in a parameter from $H_{\aleph_2}$.

Logic · Mathematics 2025-04-16 Stefan Hoffelner , Paul Larson , Ralf Schindler , Liuzhen Wu

This paper studies cardinal invariants b_kappa and t_kappa, the natural generalizations of the invariants b and t to a regular cardinal kappa.

Logic · Mathematics 2007-05-23 Saharon Shelah , Zoran Spasojević

We prove that for infinite cardinals $\kappa<\lambda$ the alternating group $Alt(\lambda)$ (of even permutations) of $\lambda$ is not embeddable into the symmetric group $Sym(\kappa)$ (of all permutations) of $\kappa$. To prove this fact we…

Group Theory · Mathematics 2016-06-23 Taras Banakh , Heike Mildenberger

It is well-known that the consistency strength of the GCH failing at a measurable cardinal is the existence of a cardinal $\kappa$ with $o(\kappa)=\kappa^{++}$. As the literature does not contain more than a proof sketch of the lower bound…

Logic · Mathematics 2025-01-03 Connor Watson

We study and classify topologically invariant sigma-ideals with an analytic base on Euclidean spaces and evaluate the cardinal characteristics of such ideals.

Logic · Mathematics 2016-02-23 Taras Banakh , Michał Morayne , Robert Rałowski , Szymon Żeberski

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

Normal ideals on regular uncountable cardinals are familiar objects. We investigate ideals that are pleasant--while a normal ideal is closed under arbitrary diagonal unions, a pleasant ideal is closed only under diagonal unions indexed by…

Logic · Mathematics 2009-09-25 Christopher Leary

We introduce the notion of $K$-ideals associated with Kuratowski partitions and we prove that each $\kappa$-complete ideal on a measurable cardinal $\kappa$ can be represented as a $K$-ideal. Moreover, we show some results concerning…

Logic · Mathematics 2017-06-28 Joanna Jureczko , Bogdan Węglorz

Assuming the existence of a strong cardinal $\kappa$ and a measurable cardinal above it, we force a generic extension in which $\kappa$ is a singular strong limit cardinal of any prescribed cofinality, and such that the tree property holds…

Logic · Mathematics 2017-08-08 Mohammad Golshani , Rahman Mohammadpour

A stationary subset $S$ of a regular uncountable cardinal $\kappa$ {\it reflects fully} at regular cardinals if for every stationary set $T \subseteq \kappa$ of higher order consisting of regular cardinals there exists an $\alpha \in T$…

Logic · Mathematics 2008-02-03 Thomas Jech , Jiří Witzany

We give some general criteria, when kappa-complete forcing preserves largeness properties -- like kappa-presaturation of normal ideals on lambda (even when they concentrate on small cofinalities). Then we quite accurately obtain the…

Logic · Mathematics 2016-09-06 Moti Gitik , Saharon Shelah

Let kappa a regular uncountable cardinal and lambda a cardinal >kappa, and suppose lambda^{<kappa} is less than the covering number for category cov(M_{kappa,kappa}). Then (a) I_{kappa,lambda}^+ -->^kappa (I_{kappa, lambda}^+,omega +1)^2,…

Logic · Mathematics 2007-05-23 Pierre Matet , Saharon Shelah

We show that the tree property, stationary reflection and the failure of approachability at $\kappa^{++}$ are consistent with $\mathfrak{u}(\kappa) = \kappa^+ < 2^\kappa$, where $\kappa$ is a singular strong limit cardinal with the…

Logic · Mathematics 2019-11-01 Radek Honzik , Sarka Stejskalova

We prove two $\mathrm{ZFC}$ inequalities between cardinal invariants. The first inequality involves cardinal invariants associated with an analytic P-ideal, in particular the ideal of subsets of $\omega$ of asymptotic density $0$. We obtain…

Logic · Mathematics 2015-05-26 Dilip Raghavan , Saharon Shelah

Working under large cardinal assumptions, we study the Borel-reducibility between equivalence relations modulo restrictions of the non-stationary ideal on some fixed cardinal $\kappa$. We show the consistency of…

Logic · Mathematics 2017-08-10 David Asperó , Tapani Hyttinen , Vadim Kulikov , Miguel Moreno