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We study models M of set theory that are "condensable", in the sense that there is an "ordinal" v of M such that the rank initial segment of M determined by v is both isomorphic to M, and also an elementary submodel of M for infinitary…

Logic · Mathematics 2021-06-21 Ali Enayat

We define a certain finite set in set theory $\{x\mid\varphi(x)\}$ and prove that it exhibits a universal extension property: it can be any desired particular finite set in the right set-theoretic universe and it can become successively any…

Logic · Mathematics 2018-06-21 Joel David Hamkins , W. Hugh Woodin

We prove in particular that, in a large class of dp-minimal theories including the p-adics, definable types are dense amongst non-forking types.

Logic · Mathematics 2014-07-02 Pierre Simon , Sergei Starchenko

In two papers we noted that in common practice many algebraic constructions are defined only `up to isomorphism' rather than explicitly. We mentioned some questions raised by this fact, and we gave some partial answers. The present paper…

Logic · Mathematics 2007-05-23 Wilfrid Hodges , Saharon Shelah

We study a class of tame $\mathcal{L}$-theories $T$ of topological fields and their $\mathcal{L}_\delta$-extension $T_{\delta}^*$ by a generic derivation $\delta$. The topological fields under consideration include henselian valued fields…

Logic · Mathematics 2022-01-26 Pablo Cubides Kovacsics , Françoise Point

We study sets and groups definable in tame expansions of o-minimal structures. Let $\mathcal {\widetilde M}= \langle \mathcal M, P\rangle$ be an expansion of an o-minimal $\mathcal L$-structure $\cal M$ by a dense set $P$, such that three…

Logic · Mathematics 2019-10-02 Pantelis E. Eleftheriou , Ayhan Günaydin , Philipp Hieronymi

In this paper, we study several finite approximation properties of topological full groups of group actions on the Cantor set such that free points are dense. Firstly, we establish that for such a distal action $\alpha$ of a countable…

Dynamical Systems · Mathematics 2024-03-07 Xin Ma

This article examines how the physical presence of field energy and particulate matter could influence the topological properties of space time. The theory is developed in terms of vector and matrix equations of exterior differential forms.…

General Relativity and Quantum Cosmology · Physics 2007-05-23 R. M. Kiehn

We study the topology of metric spaces which are definable in o-minimal expansions of ordered fields. We show that a definable metric space either contains an infinite definable discrete set or is definably homeomorphic to a definable set…

Logic · Mathematics 2015-11-12 Erik Walsberg

We prove several theorems relating amenability of groups in various categories (discrete, definable, topological, automorphism group) to model-theoretic invariants (quotients by connected components, Lascar Galois group, G-compactness,…

Logic · Mathematics 2019-01-11 Krzysztof Krupinski , Anand Pillay

The paper deals with Henselian valued field with analytic structure. Actually, we are focused on separated analytic structures, but the results remain valid for strictly convergent analytic ones as well. A classical example of the latter is…

Algebraic Geometry · Mathematics 2018-11-29 Krzysztof Jan Nowak

We construct a topos in which the Dedekind reals are countable. The topos arises from a new kind of realizability, which we call parameterized realizability, based on partial combinatory algebras whose application depends on a parameter.…

Logic · Mathematics 2026-04-02 Andrej Bauer , James E. Hanson

Definable topological groups whose topologies are affine have definable $\mathcal C^r$ structures in d-minimal expansions of ordered fields, where $r$ is a positive integer. We prove this fact using a new notion called partition degree of a…

Logic · Mathematics 2024-07-24 Masato Fujita

The Theory of Functional Connections (TFC) is most often used for constraints over the field of real numbers. However, previous works have shown that it actually extends to arbitrary fields. The evidence for these claims is restricting…

Analysis of PDEs · Mathematics 2023-03-07 Carl Leake

We prove the following theorem: let $\widetilde{\mathcal R}$ be an expansion of the real field $\overline{\mathbb R}$, such that every definable set (I) is a uniform countable union of semialgebraic sets, and (II) contains a "semialgebraic…

Logic · Mathematics 2018-12-27 Pantelis E. Eleftheriou , Alex Savatovsky

This article concerns the Herrlich-Chew theorem stating that a Hausdorff zero-dimensional space is $\mathbb{N}$-compact if and only if every clopen ultrafilter with the countable intersection property in this space is fixed. It also…

General Topology · Mathematics 2024-08-06 AliReza Olfati , Eliza Wajch

For any first order theory T we construct a Boolean valued model M, in which precisely the T--provable formulas hold, and in which every (Boolean valued) subset which is invariant under all automorphisms of M is definable by a first order…

Logic · Mathematics 2016-09-07 Carsten Butz , Ieke Moerdijk

We establish a characterization of amenability for general Hausdorff topological groups in terms of matchings with respect to finite uniform coverings. Furthermore, we prove that it suffices to just consider two-element uniform coverings.…

Group Theory · Mathematics 2018-10-16 Friedrich Martin Schneider , Andreas Thom

We develop a general ring theory in the o-minimal setting culminating in a description of all the definable rings in an arbitrary o-minimal structure. We show that every definably connected ring with non-trivial multiplication defines an…

Logic · Mathematics 2025-03-05 Annalisa Conversano

Consider a definable complete d-minimal expansion $(F, <, +, \cdot, 0, 1, \dots,)$ of an oredered field $F$. Let $X$ be a definably compact definably normal definable $C^r$ manifold and $2 \le r <\infty$. We prove that the set of definable…

Logic · Mathematics 2024-08-28 Masato Fujita , Tomohiro Kawakami