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Let a compact Lie group act ergodically on a unital $C^*$-algebra $A$. We consider several ways of using this structure to define metrics on the state space of $A$. These ways involve length functions, norms on the Lie algebra, and Dirac…

Operator Algebras · Mathematics 2007-05-23 Marc A. Rieffel

We consider endomorphism actions of arbitrary discrete semigroups on a connected metrizable topological group G. We give necessary and sufficient conditions for expansiveness of such actions when G is a Lie group or a compact…

Dynamical Systems · Mathematics 2007-05-23 Siddhartha Bhattacharya

A locally compact contraction group is a pair (G,f) where G is a locally compact group and f an automorphism of G which is contractive in the sense that the forward orbit under f of each g in G converges to the neutral element e, as n tends…

Group Theory · Mathematics 2018-04-05 Helge Glockner , George A. Willis

Word embeddings are a powerful approach for analyzing language, and exponential family embeddings (EFE) extend them to other types of data. Here we develop structured exponential family embeddings (S-EFE), a method for discovering…

Computation and Language · Computer Science 2017-10-03 Maja Rudolph , Francisco Ruiz , Susan Athey , David Blei

We are interested in classifying groups of local biholomorphisms (or even formal diffeomorphisms) that can be endowed with a canonical structure of algebraic group up to add extra formal diffeomorphisms. We show that this is the case for…

Dynamical Systems · Mathematics 2022-03-25 Javier Ribón

A group is called matricial field (MF) if it admits finite dimensional approximate unitary representations which are approximately faithful and approximately contained in the left regular representation. This paper provides a new class of…

Operator Algebras · Mathematics 2023-10-16 Christopher Schafhauser

Surface groups are determined among limit groups by their profinite completions. As a corollary, the set of surface words in a free group is closed in the profinite topology.

Group Theory · Mathematics 2020-10-16 Henry Wilton

In this note we study countable subgroups of the full group of a measure preserving equivalence relation. We provide various constraints on the group structure, the nature of the action, and on the measure of fixed point sets, that imply…

Group Theory · Mathematics 2023-09-27 Vadim Alekseev , Alessandro Carderi , Andreas Thom , Robin Tucker-Drob

By a recent result of Juh\'{a}sz and van Mill, a locally compact topological group whose dense subspaces are all separable is metrizable. In this note we investigate the following question: is every locally compact group having all dense…

Group Theory · Mathematics 2024-12-16 Dekui Peng

We provide a necessary and sufficient condition for the embeddability of a metrizable group into semigroup compactifications associated to uniformly continuous functions. Our result employs a technique used by I. Ben Yaacov, A. Berenstein…

Functional Analysis · Mathematics 2016-12-02 Camilo Gómez

We investigate whether semigroups with a given property which are also locally embeddable into finite semigroups can be locally embedded into finite semigroups with the same property, obtaining a positive answer for completely simple and…

Group Theory · Mathematics 2025-10-27 Dmitry Kudryavtsev

In this work we consider interval metrics on groups; that is, integral invariant metrics whose associated weight functions do not have gaps. We give conditions for a group to have and to have not interval metrics. Then we study Lee metrics…

Group Theory · Mathematics 2023-02-28 Ricardo A. Podestá , Maximiliano G. Vides

We initiate the study of computable presentations of real and complex C*-algebras under the program of effective metric structure theory. With the group situation as a model, we develop corresponding notions of recursive presentations and…

Logic · Mathematics 2023-04-17 Alec Fox

Researchers have recently suggested that models share common representations. In our work, we find numerous geometric similarities across the token embeddings of large language models. First, we find ``global'' similarities: token…

Computation and Language · Computer Science 2025-07-16 Andrew Lee , Melanie Weber , Fernanda Viégas , Martin Wattenberg

The framework developed in the present paper provides a formal ground to generate and study explainable categorizations of sets of entities, based on the epistemic attitudes of individual agents or groups thereof. Based on this framework,…

Artificial Intelligence · Computer Science 2024-12-30 Marcel Boersma , Krishna Manoorkar , Alessandra Palmigiano , Mattia Panettiere , Apostolos Tzimoulis , Nachoem Wijnberg

We explore the ability of word embeddings to capture both semantic and morphological similarity, as affected by the different types of linguistic properties (surface form, lemma, morphological tag) used to compose the representation of each…

Computation and Language · Computer Science 2017-04-07 Oded Avraham , Yoav Goldberg

We prove that every countable left-ordered group embeds into a finitely generated left-ordered simple group. Moreover, if the first group has a computable left-order, then the simple group also has a computable left-order. We also obtain a…

Group Theory · Mathematics 2022-03-09 Arman Darbinyan , Markus Steenbock

We consider the finitely generated groups acting on a regular tree with almost prescribed local action. We show that these groups embed as cocompact irreducible lattices in some locally compact wreath products. This provides examples of…

Group Theory · Mathematics 2020-01-24 Adrien Le Boudec

Different notions of amenability on hypergroups and their relations are studied. Developing Leptin's theorem for discrete hypergroups, we characterize the existence of a bounded approximate identity for hypergroup Fourier algebras. We study…

Functional Analysis · Mathematics 2016-02-29 Mahmood Alaghmandan

We characterise the simplicity of metric ultraproducts of a family of metric groups. We also present several new examples of simple groups, such as metric ultraproducts of finite and infinite symmetric groups, linear groups, and interval…

Group Theory · Mathematics 2024-09-30 Jakub Gismatullin , Krzysztof Majcher , Martin Ziegler