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We give a full classification, up to equivalence, of finite-dimensional graded division algebras over the field of real numbers. The grading group is any abelian group.

Rings and Algebras · Mathematics 2018-03-06 Yuri Bahturin , Mikhail Zaicev

We investigate the computability-theoretic properties of valued fields, and in particular algebraically closed valued fields and $p$-adically closed valued fields. We give an effectiveness condition, related to Hensel's lemma, on a valued…

Logic · Mathematics 2017-09-29 Matthew Harrison-Trainor

In his unpublished preprint "Definable Valuations" Koenigsmann shows that every field that admits a t-henselian topology is either real closed or separably closed or admits a definable valuation inducing the t-henselian topology. To show…

Logic · Mathematics 2016-03-31 Katharina Dupont

We prove some technical results on definable types in $p$-adically closed fields, with consequences for definable groups and definable topological spaces. First, the code of a definable $n$-type (in the field sort) can be taken to be a real…

Logic · Mathematics 2024-07-18 Pablo Andujar Guerrero , Will Johnson

We give an explicit algebraic characterisation of all definable henselian valuations on a dp-minimal real field. Additionally we characterise all dp-minimal real fields that admit a definable henselian valuation with real closed residue…

Logic · Mathematics 2024-10-15 Lothar Sebastian Krapp , Salma Kuhlmann , Lasse Vogel

The classification of gradings by abelian groups on finite direct sums of simple finite-dimensional nonassociative algebras over an algebraically closed field is reduced, by means of the use of loop algebras, to the corresponding problem…

Rings and Algebras · Mathematics 2019-04-25 Alejandra S. Córdova-Martínez , Alberto Elduque

We give a characterization of limits of dihedral groups in the space of finitely generated marked groups. We also describe the topological closure of dihedral groups in the space of marked groups on a fixed number of generators.

Group Theory · Mathematics 2007-10-09 Luc Guyot

We consider an action of a countable amenable group on a compact metric space, focusing on the set of generic points with respect to a fixed F{\o}lner sequence. For a given characteristic class, we prove that the set of points that are…

Dynamical Systems · Mathematics 2025-10-31 Sejal Babel , Martha Łącka , Marcel Mroczek

We entirely classify definable sets up to definable bijections in $\mathbb{Z}$-groups, where the language is the one of ordered abelian groups. From this, we deduce, among others, a classification of definable families of bounded definable…

Logic · Mathematics 2018-01-17 Raf Cluckers , Immanuel Halupczok

Let $\mathcal G$ denote the space of finitely generated marked groups. For any finitely generated group $G$, we construct a continuous, injective map $f$ from the space of subgroups $Sub(G)$ to $\mathcal G$ that sends conjugate subgroups to…

Group Theory · Mathematics 2024-03-27 D. Osin

We consider the problem of classifying gradings by groups on a finite-dimensional algebra $A$ (with any number of multilinear operations) over an algebraically closed field. We introduce a class of gradings, which we call almost fine, such…

Rings and Algebras · Mathematics 2025-06-24 Alberto Elduque , Mikhail Kochetov

We classify, up to equivalence, all finite-dimensional simple graded division algebras over the field of real numbers. The grading group is any finite abelian group.

Rings and Algebras · Mathematics 2015-06-09 Yuri Bahturin , Mikhail Zaicev

Universality has been an important concept in computable structure theory. A class $\mathcal{C}$ of structures is universal if, informally, for any structure, of any kind, there is a structure in $\mathcal{C}$ with the same…

Logic · Mathematics 2017-12-05 Matthew Harrison-Trainor , Meng-Che Ho

In a stable abelian group, we characterize generic types of cosets of type-definable subgroups.

Logic · Mathematics 2007-05-23 Martin Ziegler

In this paper, we classify the possible group structures on the set of $R$-valued points of an abelian variety, where $R$ is any real closed field. We make use of a family of abelian varieties that, in effect, allows one to quantify over…

Algebraic Geometry · Mathematics 2023-05-31 Nathanial Lowry

We investigate the computability of algebraic closure and definable closure with respect to a collection of formulas. We show that for a computable collection of formulas of quantifier rank at most $n$, in any given computable structure,…

Logic · Mathematics 2021-03-10 Nathanael Ackerman , Cameron Freer , Rehana Patel

Given a fine abelian group grading on a finite dimensional simple Lie algebra over an algebraically closed field of characteristic zero, with universal grading group $G$, it is shown that the induced grading by the free group $G/\tor(G)$ is…

Rings and Algebras · Mathematics 2013-03-05 Alberto Elduque

We shall define a general notion of dimension, and study groups and rings whose interpretable sets carry such a dimensio. In particular, we deduce chain conditions for groups, definability results for fields and domains, and show that…

Logic · Mathematics 2019-09-04 Frank Olaf Wagner

Algebraic structures such as monoids, groups, and categories can be formulated within a category using commutative diagrams. In many common categories these reduce to familiar cases. In particular, group objects in Grp are abelian groups,…

Category Theory · Mathematics 2007-05-23 Magnus Forrester-Barker

We prove that bounded conciseness is a closed property in the space of marked groups. As a consequence, we reformulate a conjecture of Fern\'andez-Alcober and Shumyatsky [7] about conciseness in the class of residually finite groups.

Group Theory · Mathematics 2025-02-10 Federico Berlai