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200 papers

Proper group actions are ubiquitous in mathematics and have many of the attractive features of actions of compact groups. In this survey, we discuss proper actions of Lie groups on smooth manifolds. If the group dimension is sufficiently…

Complex Variables · Mathematics 2015-02-02 Alexander Isaev

We prove that for certain actions of a discrete countable residually finite amenable group acting on a compact metric space with specification property, periodic measures are dense in the set of invariant measures.

Dynamical Systems · Mathematics 2015-10-20 Xiankun Ren

We study equivariant unirationality of actions of finite groups on tori of small dimensions.

Algebraic Geometry · Mathematics 2025-09-23 Yuri Tschinkel , Zhijia Zhang

We prove that, if a discrete group $G$ is not inner amenable, then the unit group of the ring of operators affiliated with the group von Neumann algebra of $G$ is non-amenable with respect to the topology generated by its rank metric. This…

Operator Algebras · Mathematics 2025-03-04 Friedrich Martin Schneider

We formulate some problems and conjectures about semigroups of rational functions under composition. The considered problems arise in different contexts, but most of them are united by a certain relationship to the concept of amenability.

Dynamical Systems · Mathematics 2022-02-24 Fedor Pakovich

We study strongly outer actions of discrete groups on C*-algebras in relation to (non)amenability. In contrast to related results for amenable groups, where uniqueness of strongly outer actions on the Jiang-Su algebra is expected, we show…

Operator Algebras · Mathematics 2018-03-19 Eusebio Gardella , Martino Lupini

Let $\varphi$ and $\varphi'$ be two homotopic actions of the topological group $G$ on the topological space $X$. To an object $A$ in the $G$-equivariant derived category $D_{\varphi}(X)$ of $X$ relative to the action $\varphi$ we associate…

Algebraic Topology · Mathematics 2016-05-23 Andrés Viña

We prove pointwise and maximal ergodic theorems for probability measure preserving (p.m.p.) actions of any countable group, provided it admits an essentially free, weakly mixing amenable action of stable type $III_1$. We show that this…

Dynamical Systems · Mathematics 2011-12-30 Lewis Bowen , Amos Nevo

We characterize rational actions of the additive group on algebraic varieties defined over a field of characteristic zero in terms of a suitable integrability property of their associated velocity vector fields. This extends the classical…

Algebraic Geometry · Mathematics 2014-09-23 Adrien Dubouloz , Alvaro Liendo

We prove that amenability of a discrete group is equivalent to dimension flatness of certain ring inclusions naturally associated with measure preserving actions of the group. This provides a group-measure space theoretic solution to a…

Group Theory · Mathematics 2013-05-16 David Kyed , Henrik Densing Petersen

In the current paper we attempt to transfer the notion of the projectional entropy, originally defined for multidimensional subshifts, to the case of actions of amenable groups. The main theorem states that if a system is strongly…

Dynamical Systems · Mathematics 2024-03-05 Michał Prusik

Given a countable amenable group G and 0 < L < 1, we give an elementary construction of a type-III:L Bernoulli group action. In the case where G is the integers, we show that our nonsingular Bernoulli shifts have independent and identically…

Dynamical Systems · Mathematics 2021-01-29 Zemer Kosloff , Terry Soo

We show that if a (locally compact) group $G$ acts properly on a locally compact $\sigma$-compact space $X$ then there is a family of $G$-invariant proper continuous finite-valued pseudometrics which induces the topology of $X$. If $X$ is…

Metric Geometry · Mathematics 2014-02-26 Herbert Abels , Antonios Manoussos , Gennady Noskov

This is the second one in a series of papers classifying the factorizations of almost simple groups with nonsolvable factors. In this paper we deal with almost simple unitary groups.

Group Theory · Mathematics 2021-08-03 Cai Heng Li , Lei Wang , Binzhou Xia

We define a class of finite groups based on the properties of the closed twins of their power graphs and study the structure of those groups. As a byproduct, we obtain results about finite groups admitting a partition by cyclic subgroups.

Group Theory · Mathematics 2024-12-23 Daniela Bubboloni , Nicolas Pinzauti

In the first part of this work we have established an efficient method to obtain a topological classification of locally discrete, finitely generated, virtually free subgroups of real-analytic circle diffeomorphisms. In this second part we…

We consider actions of a group or a semigroup on a set, which generalize the setup of discrete logarithm based cryptosystems. Such cryptographic group actions have gained increasing attention recently in the context of isogeny-based…

Cryptography and Security · Computer Science 2023-01-05 Oliver W. Gnilke , Jens Zumbrägel

We develop in this paper some general techniques to analyze action sets of small doubling for probability measure-preserving actions of amenable groups. As an application of these techniques, we prove a dynamical generalization of Kneser's…

Dynamical Systems · Mathematics 2019-05-24 Michael Björklund , Alexander Fish

This paper develops some general results about actions of finite groups on (infinite) abelian groups in the finite Morley rank category. They are linked to a range of problems on groups of finite Morley rank discussed in [16]. Crucially,…

Group Theory · Mathematics 2024-07-24 Alexandre Borovik

We review subbadditivity properties of Shannon entropy, in particular, from the Shearer's inequality we derive the "infimum rule" for actions of amenable groups. We briefly discuss applicability of the "infimum formula" to actions of other…

Dynamical Systems · Mathematics 2015-02-27 Tomasz Downarowicz , Bartosz Frej , Pierre-Paul Romagnoli