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We describe a proof-theoretic bound on $Sigma_{2}$-definable countable ordinals in Kripke-Platek set theory with $Pi_{1}$-Collection and the existence of $omega_{1}$.

Logic · Mathematics 2015-08-10 Toshiyasu Arai

We construct a homogeneous subspace of $2^\omega$ whose complement is dense in $2^\omega$ and rigid. Using the same method, assuming Martin's Axiom, we also construct a countable dense homogeneous subspace of $2^\omega$ whose complement is…

General Topology · Mathematics 2014-10-03 Andrea Medini , Jan van Mill , Lyubomyr Zdomskyy

Recently there have been discussions about which complex metrics should be allowable in quantum gravity. These discussions assumed that the matter fields were real valued. We make the observation that for compactified solutions it makes…

High Energy Physics - Theory · Physics 2023-02-22 Jean-Luc Lehners

We completely characterize the finite dimensional subsets A of any separable Hilbert space for which the notion of A-hypercyclicity coincides with the notion of hypercyclicity, where an operator T on a topological vector space X is said to…

Functional Analysis · Mathematics 2018-08-17 S. Charpentier , R. Ernst

We characterize the finite dimensional asymmetric normed spaces which are right bounded and the relation of this property with the natural compactness properties of the unit ball, as compactness and strong compactness. In contrast with some…

General Topology · Mathematics 2017-02-15 Natalia Jonard-Pérez , Enrique A. Sánchez-Pérez

We prove that consistently there is a singular cardinal $\kappa$ of uncountable cofinality such that $2^\kappa$ is weakly inaccessible, and every regular cardinal strictly between $\kappa$ and $2^\kappa$ is the character of some uniform…

Logic · Mathematics 2019-07-30 James Cummings , Charles Morgan

The set of answers to a query may be very large, potentially overwhelming users when presented with the entire set. In such cases, presenting only a small subset of the answers to the user may be preferable. A natural requirement for this…

Databases · Computer Science 2024-08-06 Marcelo Arenas , Timo Camillo Merkl , Reinhard Pichler , Cristian Riveros

Maximal supergravity solutions are revisited and classified, with particular emphasis on objects of co-dimension at most two. This class of solutions includes branes whose tension scales with g_s^{-\sigma} for \sigma>2. We present a group…

High Energy Physics - Theory · Physics 2015-05-30 Axel Kleinschmidt

A space has $\sigma$-compact tightness if the closures of $\sigma$-compact subsets determines the topology. We consider a dense set variant that we call densely k-separable. We consider the question of whether every densely k-separable…

General Topology · Mathematics 2018-10-12 Alan Dow , Istvan Juhasz

A "2-group" is a category equipped with a multiplication satisfying laws like those of a group. Just as groups have representations on vector spaces, 2-groups have representations on "2-vector spaces", which are categories analogous to…

Quantum Algebra · Mathematics 2013-05-17 John C. Baez , Aristide Baratin , Laurent Freidel , Derek K. Wise

We investigate which definable separable metric spaces are countable dense homogeneous (CDH). We prove that a Borel CDH space is completely metrizable and give a complete list of zero-dimensional Borel CDH spaces. We also show that for a…

General Topology · Mathematics 2013-10-09 Michael Hrusak , Beatriz Zamora Aviles

In [1] the authors showed some basic properties of a pre-order that arose in combinatorial number theory, namely the finite embeddability between sets of natural numbers, and they presented its generalization to ultrafilters, which is…

Logic · Mathematics 2014-06-13 Lorenzo Luperi Baglini

We show relative to strong hypotheses that patterns of compact cardinals in the universe, where a compact cardinal is one which is either strongly compact or supercompact, can be virtually arbitrary. Specifically, we prove if V is a model…

Logic · Mathematics 2007-05-23 Arthur W. Apter

Recent advances in our understanding of higher derived limits carry multiple implications in the fields of condensed and pyknotic mathematics, as well as for the study of strong homology. These implications are thematically diverse,…

Algebraic Topology · Mathematics 2025-08-12 Jeffrey Bergfalk , Chris Lambie-Hanson

In this paper we are concerned with the recent summability notion of I-statistically pre-Cauchy real double sequences in line of Das et. al. [6] as a generalization of I-statistical convergence. Here we introduce the notion of double…

Functional Analysis · Mathematics 2017-03-22 Prasanta Malik , Argha Ghosh

Two-dimensional random tilings of rhombi can be seen as projections of two-dimensional membranes embedded in hypercubic lattices of higher dimensional spaces. Here, we consider tilings projected from a $D$-dimensional space. We study the…

Statistical Mechanics · Physics 2016-08-31 N. Destainville , M. Widom , R. Mosseri , F. Bailly

As defined in [1], a Hausdorff space is strongly anti-Urysohn (in short: SAU) if it has at least two non-isolated points and any two infinite} closed subsets of it intersect. Our main result answers the two main questions of [1] by…

General Topology · Mathematics 2021-06-02 István Juhász , Saharon Shelah , LAjos Soukup , Zoltán Szentmiklóssy

All constructive methods employed in modern mathematics produce only countable sets, even when designed to transcend countability. We show that any constructive argument for uncountability -- excluding diagonalization techniques --…

General Mathematics · Mathematics 2025-05-28 Stanislav Semenov

Let $X$ be a Banach space, let $(\Omega,\mu)$ be a $\sigma$-finite measure space and let $A,B\colon\Omega\to B(X)$ be strongly measurable $\gamma$-bounded functions. We show that for all $x\in X$ and all $x^*\in X^*$, there exist a Hilbert…

Functional Analysis · Mathematics 2024-02-19 Christian Le Merdy

A set A of natural numbers is finitely embeddable in another such set B if every finite subset of A has a rightward translate that is a subset of B. This notion of finite embeddability arose in combinatorial number theory, but in this paper…

Logic · Mathematics 2015-12-11 Andreas Blass , Mauro Di Nasso