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A cardinal kappa is countably closed if mu^omega < kappa whenever mu < kappa. Assume that there is no inner model with a Woodin cardinal and that every set has a sharp. Let K be the core model. Assume that kappa is a countably closed…

Logic · Mathematics 2016-09-07 William J. Mitchell , Ernest Schimmerling , John R. Steel

We prove a weakened version of the reflection of Reinhardt cardinals by super Reinhardt cardinals: Let $M=(V^M,P)$ be a countable model of second order set theory $\mathsf{ZF}_2$ (with universe $V^M$ and classes $P$) which models "$\kappa$…

Logic · Mathematics 2020-05-25 Farmer Schlutzenberg

We characterize several large cardinal notions by model-theoretic properties of extensions of first-order logic. We show that $\Pi_n$-strong cardinals, and, as a corollary, ``Ord is Woodin" and weak Vop\v{e}nka's Principle, are…

Logic · Mathematics 2025-05-22 Will Boney , Jonathan Osinski

We provide a model theoretical and tree property like characterization of $\lambda$-$\Pi^1_1$-subcompactness and supercompactness. We explore the behaviour of those combinatorial principles at accessible cardinals.

Logic · Mathematics 2022-02-03 Yair Hayut , Menachem Magidor

We show that the existence of a weakly compact cardinal over the Zermelo-Fraenkel's set theory is proof-theoretically reducible to iterations of Mostowski collapsings and Mahlo operations.

Logic · Mathematics 2013-04-11 Toshiyasu Arai

We call a subset of an ordinal $\lambda$ recognizable if it is the unique subset $x$ of $\lambda$ for which some Turing machine with ordinal time and tape, which halts for all subsets of $\lambda$ as input, halts with the final state $0$.…

Logic · Mathematics 2026-05-19 Merlin Carl , Philipp Schlicht , Philip Welch

In this article, we give a proof for that the cardinality of a function basis of the invariants for a finite dimensional real vector space by a compact group is lower bounded by the intuitive difference of the dimensions of the vector space…

Algebraic Geometry · Mathematics 2018-08-06 Shenglong Hu , Liqun Qi

We answer the question, raised more than thirty years ago, on whether the power (G raised to the power omega) of a countably compact minimal Abelian group G is minimal, by showing that the negative answer is equivalent to the existence of…

Logic · Mathematics 2021-12-17 Dikran Dikranjan , Vladimir Uspenskij

An elementary embedding $j:M\rightarrow N$ between two inner models of ZFC is cardinal preserving if $M$ and $N$ correctly compute the class of cardinals. We look at the case $N=V$ and show that there is no nontrivial cardinal preserving…

Logic · Mathematics 2024-11-05 Gabriel Goldberg , Sebastiano Thei

We introduce the notion of W-measurable sensitivity, which extends and strictly implies canonical measurable sensitivity, a measure- theoretic version of sensitive dependence on initial conditions. This notion also implies pairwise…

Dynamical Systems · Mathematics 2012-08-20 Ilya Grigoriev , Nathaniel Ince , Marius Catalin Iordan , Amos Lubin , Cesar E. Silva

We prove that on many inaccessible there is a Jonsson algebra, so e.g. the first regular Jonsson cardinal lambda which is lambda x omega-Mahlo. We give further restrictions on successor of singulars which are Jonsson cardinals. E.g. there…

Logic · Mathematics 2007-05-23 Saharon Shelah

Assume ZF($j$) and there is a Reinhardt cardinal, as witnessed by the elementary embedding $j:V\to V$. We investigate the linear iterates $(N_{\alpha},j_{\alpha})$ of $(V,j)$, and their relationship to $(V,j)$, forcing and definability,…

Logic · Mathematics 2020-06-30 Farmer Schlutzenberg

Assume G.C.H. and kappa is the first uncountable cardinal such that there is a kappa-free abelian group which is not a Whitehead (abelian) group. We prove that kappa is necessarily an inaccessible cardinal

Logic · Mathematics 2011-06-13 Saharon Shelah

Motivated by recent work of Boney, Dimopoulos, Gitman and Magidor, we characterize the existence of weak compactness cardinals for all abstract logics through combinatorial properties of the class of ordinals. This analysis is then used to…

Logic · Mathematics 2025-05-22 Philipp Lücke

This work makes explicit the degrees of freedom involved in modeling the dynamics of a network, or some other first-order property of a network, such as a measurement function. In previous work, an admissible function in a network was…

Optimization and Control · Mathematics 2022-11-15 Pedro Sequeira , João P. Hespanha , A. Pedro Aguiar

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

Answering a question of Usuba, we show that an extendible cardinal can be preserved by a set forcing that is not a small forcing.

Logic · Mathematics 2021-08-17 Gabriel Goldberg

Given an arbitrary measurable cardinal $\kappa$, a nondiscrete Hausdorff extremally disconnected topological group of cardinality $\kappa$ is constructed.

General Topology · Mathematics 2021-04-27 Ol'ga Sipacheva

We show that it is consistent that for some uncountable cardinal k, all compactifications of the countable discrete space with remainders homeomorphic to $D^k$ are homeomorphic to each other. On the other hand, there are $2^c$ pairwise…

General Topology · Mathematics 2007-05-23 Mikhail Matveev

We show that the consistency of $\mathrm{ZF} + \mathrm{AD}_{\mathbb{R}} + ``\Theta$ is measurable$"$ implies the consistency of $\mathrm{ZF} +``\Theta$ is the least strongly regular cardinal and the least measurable cardinal$"$ + $``$all…

Logic · Mathematics 2026-03-11 Rahman Mohammadpour , Otto Rajala , Sebastiano Thei