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Let $\big(\mathcal{S}_n^{\alpha,\kappa,\mathfrak{r}}(z)\big)_{n=1}^\infty$ be a sequence of the largest possible integer intervals, such that…

General Mathematics · Mathematics 2020-04-09 Andrzej Bożek

Given a module $X$ and a regular cardinal $\kappa$ we study various notions of $(\kappa,\mathrm{Add}(X))$-freeness and $(\kappa,\mathrm{Add}(X))$-separability. Bearing on appropriate set-theoretic assumptions, we construct a non-trivial…

Rings and Algebras · Mathematics 2024-07-31 Manuel Cortés-Izurdiaga , Alejandro Poveda

For an inaccessible cardinal $\kappa$, the super tree property (ITP) at $\kappa$ holds if and only if $\kappa$ is supercomact. However, just like the tree property, it can hold at successor cardinals. We show that ITP holds at the successor…

Logic · Mathematics 2018-06-05 Sherwood Hachtman , Dima Sinapova

We consider the following dichotomy for $\Sigma^0_2$ finitary relations $R$ on analytic subsets of the generalized Baire space for $\kappa$: either all $R$-independent sets are of size at most $\kappa$, or there is a $\kappa$-perfect…

Logic · Mathematics 2016-09-16 Dorottya Sziráki , Jouko Väänänen

We study the existence and cardinality of universal families for classes of rayless graphs. It is known, by a result of Diestel, Halin, and Vogler, that the class of countable rayless graphs does not admit a countable universal family,…

Combinatorics · Mathematics 2025-12-18 Leandro Fiorini Aurichi , Guilherme Eduardo Pinto

We prove that some natural "outside" property is equivalent (for a first order class) to being stable. For a model, being resplendent is a strengthening of being kappa-saturated. Restricting ourselves to the case kappa > |T| for…

Logic · Mathematics 2022-10-18 Saharon Shelah

Let $\mathcal{I}$ be an ideal on $\omega$. For $f,g\in\omega^\omega$ we write $f \leq_{\mathcal{I}} g$ if $f(n) \leq g(n)$ for all $n\in\omega\setminus A$ with some $A\in\mathcal{I}$. Moreover, we denote…

Logic · Mathematics 2023-08-01 Rafał Filipów , Adam Kwela

For a cardinal $\kappa > \omega$ a metric space $X$ is called to be $\kappa$-superuniversal whenever for every metric space $Y$ with $|Y| < \kappa$ every partial isometry from a subset of $Y$ into $X$ can be extended over the whole space…

General Topology · Mathematics 2014-07-15 Wojciech Bielas

An independent set in a graph is a set of pairwise non-adjacent vertices, and alpha(G) is the size of a maximum independent set in the graph G. A matching is a set of non-incident edges, while mu(G) is the cardinality of a maximum matching.…

Discrete Mathematics · Computer Science 2011-05-12 Vadim E. Levit , Eugen Mandrescu

The current paper answers an open question of abs/1007.2426 We say that a countable model M characterizes an infinite cardinal kappa, if the Scott sentence of M has a model in cardinality kappa, but no models in cardinality kappa plus. If M…

Logic · Mathematics 2012-05-07 Ioannis Souldatos

We present an overview of results on the question of whether the non-stationary ideal of an uncountable regular cardinal $\kappa$ can be defined by a $\Pi_1$-formula using parameters of hereditary cardinality at most $\kappa$. These results…

Logic · Mathematics 2024-04-18 Philipp Lücke

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 show that all sufficiently nice $\lambda$-sets are countable dense homogeneous ($\mathsf{CDH}$). From this fact we conclude that for every uncountable cardinal $\kappa \le \mathfrak{b}$ there is a countable dense homogeneous metric space…

General Topology · Mathematics 2018-09-19 Rodrigo Hernández-Gutiérrez , Michael Hrušák , Jan van Mill

Suppose that lambda = mu^+. We consider two aspects of the square property on subsets of lambda. First, we have results which show e.g. that for aleph_0 <= kappa =cf (kappa)< mu, the equality cf([mu]^{<= kappa}, subseteq)= mu is a…

Logic · Mathematics 2016-09-06 Mirna Džamonja , Saharon Shelah

In [8] the second and third authors showed that if the least inaccessible cardinal is the least measurable cardinal, then there is an inner model with $o(\kappa)\geq2$. In this paper we improve this to $o(\kappa)\geq\kappa+1$ and show that…

Logic · Mathematics 2024-12-17 Moti Gitik , Yair Hayut , Asaf Karagila

The main result of this paper is a generalization of Popa's free independence result for subalgebras of ultraproduct ${\rm II_1}$ factors [Po95] to the framework of ultraproduct von Neumann algebras $(M^\omega, \varphi^\omega)$ where $(M,…

Operator Algebras · Mathematics 2015-07-29 Cyril Houdayer , Yusuke Isono

We show that if $\mu \leq \cf \lambda $ and $\lambda$ is a strong limit singular cardinal, then $[\mu, \lambda ]$-compactness is productive if and only if either $\mu= \omega $, or $\mu$ is $\lambda$-strongly compact.

General Topology · Mathematics 2012-11-29 Paolo Lipparini

For an infinite cardinal $\kappa$, let $ded\kappa$ denote the supremum of the number of Dedekind cuts in linear orders of size $\kappa$. It is known that $\kappa<ded\kappa\leq 2^{\kappa}$ for all $\kappa$ and that $ded\kappa<2^{\kappa}$ is…

Logic · Mathematics 2019-02-20 Artem Chernikov , Saharon Shelah

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 can generalize the definition of {\it splitting number } $s(\kappa )$ for $\kappa$ uncountable regular: $s(\kappa )=min\{ |\Cal S|:\Cal S\subset \Cal P(\kappa ) \forall a\in \kappa ^\kappa \exists b\in \Cal S |a\cap b|=|a\setminus…

Logic · Mathematics 2008-02-03 Jindřich Zapletal