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In this paper we address the question: How many pairwise non-isomorphic extremely amenable groups are there which are separable metrizable or even Polish? We show that there are continuum many such groups. In fact we construct continuum…

Logic · Mathematics 2026-03-23 Mahmood Etedadialiabadi , Su Gao , Feng Li , Ruiwen Li

We show that connected separable locally compact groups are infinitesimally finitely generated, meaning that there is an integer $n$ such that every neighborhood of the identity contains $n$ elements generating a dense subgroup. We…

Group Theory · Mathematics 2016-03-15 Tsachik Gelander , François Le Maître

We study from the perspective of Borel complexity theory the classification problem for multiplier algebras associated with operator algebraic varieties. These algebras are precisely the multiplier algebras of irreducible complete…

Operator Algebras · Mathematics 2020-09-23 Michael Hartz , Martino Lupini

We prove that there exists a countable metrizable topological group $G$ such that every countable metrizable group is isomorphic to a quotient of $G$. The completion $H$ of $G$ is a Polish group such that every Polish group is isomorphic to…

Group Theory · Mathematics 2021-08-31 Vladimir G. Pestov , Vladimir V. Uspenskij

We investigate some properties of topological groups related to disconnectedness or Archimedeanness. We prove or disprove the preservation of those under operations as subgroups, quotients, products, etc. Characterizations of…

General Topology · Mathematics 2007-05-23 Masasi Higasikawa

When $G$ is a Polish group, metrizability of the universal minimal flow has been shown to be a robust dividing line in the complexity of the topological dynamics of $G$. We introduce a class of groups, the CAP groups, which provides a neat…

Dynamical Systems · Mathematics 2023-02-06 Gianluca Basso , Andy Zucker

We give strong necessary conditions on the admissibility of a Polish group topology for an arbitrary graph product of groups $G(\Gamma, G_a)$, and use them to give a characterization modulo a finite set of nodes. As a corollary, we give a…

Logic · Mathematics 2018-09-26 Gianluca Paolini , Saharon Shelah

The main aim of the paper is to introduce the concept of metric duality in the category of topological Abelian groups that extends the classical notion of duality for normed vector spaces and behaves quite nicely for LCA groups (equipped…

Group Theory · Mathematics 2024-12-17 Piotr Niemiec

Let $V$ be a finite dimensional complex vector space and $W\subset \GL(V)$ be a finite complex reflection group. Let $V^{\reg}$ be the complement in $V$ of the reflecting hyperplanes. A classical conjecture predicts that $V^{\reg}$ is a…

Geometric Topology · Mathematics 2007-05-23 David Bessis

We begin by introducing schemes of binoids, invertible $\mathcal{O}_M$-sets and cohomology of sheaves of abelian groups defined on schemes of binoids. We define the so-called punctured combinatorial \v{C}ech-Picard complex, whose first…

Commutative Algebra · Mathematics 2016-11-09 Davide Alberelli

Using the \texttt{WeylModules} \textsf{GAP} Package, we compute structural information about certain Weyl modules for type $G_2$ in characteristic $2$. This gives counterexamples to two conjectures stated by S.~Donkin in 1990. It also…

Representation Theory · Mathematics 2025-09-11 Stephen Doty

In this work, we introduce a class of Timmermann's measured multiplier Hopf *-algebroids called algebraic quantum transformation groupoids of compact type. Each object in this class admits a Pontrjagin-like dual called an algebraic quantum…

Quantum Algebra · Mathematics 2023-07-03 Frank Taipe

For any finite abelian group G, we study the moduli space of abelian $G$-covers of elliptic curves, in particular identifying the irreducible components of the moduli space. We prove that, in the totally ramified case, the moduli space has…

Algebraic Geometry · Mathematics 2015-06-01 Nicola Pagani

We determine the exact complexity of classifying compact metric spaces up to homeomorphism. More precisely, the homeomorphism relation on compact metric spaces is Borel bi-reducible with the complete orbit equivalence relation of Polish…

Logic · Mathematics 2014-09-22 Joseph Zielinski

We address two properties for Abelian topological groups: ``every closed subgroup is dually closed'' and ``every closed subgroup is dually embedded.'' We exhibit a pair of topological groups such that each has both of the properties and the…

General Topology · Mathematics 2007-05-23 Masasi Higasikawa

Abelian codes and complementary dual codes form important classes of linear codes that have been extensively studied due to their rich algebraic structures and wide applications. In this paper, a family of abelian codes with complementary…

Information Theory · Computer Science 2017-10-16 Arunwan Boripan , Somphong Jitman , Patanee Udomkavanich

A Polish group $G$ is called a group of quasi-invariance or a QI-group, if there exist a locally compact group $X$ and a probability measure $\mu$ on $X$ such that 1) there exists a continuous monomorphism of $G$ to $X$, and 2) for each…

General Topology · Mathematics 2009-10-01 S. S. Gabriyelyan

The class of locally compact near abelian groups is introduced and investigated as a class of metabelian groups formalizing and applying the concept of scalar multiplication. The structure of locally compact near abelian groups and its…

Group Theory · Mathematics 2017-02-14 Karl H. Hofmann , Wolfgang Herfort , Francesco G. Russo

The goal of this paper is to study the Pontrjagin dual of (reduced) 4-dimensional Spin bordism. That is to say, we consider the functor from the category of topological spaces to the category of compact abelian groups that associates to…

Geometric Topology · Mathematics 2018-03-23 Greg Brumfiel , John Morgan

Using an approach to the Jacobian Conjecture by L.M. Dru\.zkowski and K. Rusek 12], G. Gorni and G. Zampieri [19], and A.V. Yagzhev[27], we describe a correspondence between finite dimensional symmetric algebras and homogeneous tuples of…

Algebraic Geometry · Mathematics 2020-01-03 Ualbai Umirbaev