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Any finite set of linear operators on an algebra $A$ yields an operator algebra $B$ and a module structure on A, whose endomorphism ring is isomorphic to a subring $A^B$ of certain invariant elements of $A$. We show that if $A$ is a…

Rings and Algebras · Mathematics 2013-02-26 Inês Borges , Christian Lomp

We define the decomposition property for partial actions of discrete groups on $C^*$-algebras. Decomposable partial systems appear naturally in practice, and many commonly occurring partial actions can be decomposed into partial actions…

Operator Algebras · Mathematics 2022-01-25 Fernando Abadie , Eusebio Gardella , Shirly Geffen

We provide a framework for studying concrete C*-algebras associated with algebraic actions of semigroups: Given such an action, we construct an inverse semigroup, and we introduce conditions for algebraic actions that characterize…

Operator Algebras · Mathematics 2024-01-25 Chris Bruce , Xin Li

Using ultrapowers of $C^{\ast}$-algebras we provide a new construction of the multiplier algebra of a $C^{\ast}$-algebra. This extends the work of Avsec and Goldbring [Houston J. Math., to appear, arXiv:1610.09276.] to the setting of…

Operator Algebras · Mathematics 2019-07-19 Facundo Poggi , Roman Sasyk

Computational effects are commonly modelled by monads, but often a monad can be presented by an algebraic theory of operations and equations. This talk is about monads and algebraic theories for languages for inference, and their…

Logic in Computer Science · Computer Science 2023-12-29 Cristina Matache , Sean Moss , Sam Staton , Ariadne Si Suo

We prove that a countable dimensional associative algebra (resp. a countable semigroup) of locally subexponential growth is $M_\infty$-embeddable as a left ideal in a finitely generated algebra (resp. semigroup) of subexponential growth.…

Rings and Algebras · Mathematics 2017-03-28 Adel Alahmadi , Hamed Alsulami , S. K. Jain , Efim Zelmanov

We extend the definition of algebraic entropy to a class of differential-delay equations. The vanishing of the entropy, as a structural property of an equation, signals its integrability. We suggest a simple way to produce…

Exactly Solvable and Integrable Systems · Physics 2014-08-27 Claude M. Viallet

We study properties of the Weyl pseudometric associated with an action of a countable amenable group on a compact metric space. We prove that the topological entropy and the number of minimal subsets of the closure of an orbit are both…

Dynamical Systems · Mathematics 2018-08-01 Martha Łącka , Marta Straszak

An \textit{algebraic} action of a discrete group $\Gamma $ is a homomorphism from $\Gamma $ to the group of continuous automorphisms of a compact abelian group $X$. By duality, such an action of $\Gamma $ is determined by a module…

Dynamical Systems · Mathematics 2013-12-12 Hanfeng Li , Jesse Peterson , Klaus Schmidt

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 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 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

The aim of this manuscript is to study some local properties of the topological entropy of a free semigroup action. In order to do that we focus on the set of entropy points of a free semigroup action, show that this set carries the full…

Dynamical Systems · Mathematics 2021-12-22 Fagner B. Rodrigues , Thomas Jacobus , Marcus V. Silva

We develop a semigroup approach to representation theory for pro-Lie groups satisfying suitable amenability conditions. As an application of our approach, we establish a one-to-one correspondence between equivalence classes of unitary…

Representation Theory · Mathematics 2016-06-07 Daniel Beltita , Amel Zergane

We introduce invertible subalgebras of local operator algebras on lattices. An invertible subalgebra is defined to be one such that every local operator can be locally expressed by elements of the inveritible subalgebra and those of the…

Mathematical Physics · Physics 2023-11-06 Jeongwan Haah

We study the word length entropy of automorphisms of residually nilpotent groups, and how the entropy of such group automorphisms relates to the entropy of induced automorphisms on various nilpotent quotients. We show that much like the…

Group Theory · Mathematics 2011-10-05 Thomas Koberda

In this paper we introduce the definition of entropy for a partial $\mathbb{Z}$-action. We show that the definition of partial entropy is an extension of the definition of topological entropy for a $\mathbb Z$-action. We also prove that the…

Dynamical Systems · Mathematics 2021-07-30 A. Baraviera , Daniel Gonçalves , Danilo Royer , Ruy Exel , Fagner B. Rodrigues

Let A be a unitary algebra and G be a finite abelian group. Then a G-graded algebra is merely a G-algebra and viceversa because of the fact that G and its group of characters G* are isomorphic. This fact is no longer true if we substitute G…

Rings and Algebras · Mathematics 2012-11-29 Lucio Centrone

In this article, we prove Neveu decomposition for the action of the locally compact amenable semigroup of positive contractions on semifinite von Neumann algebras and thus, it entirely resolves the problem for the actions of arbitrary…

Operator Algebras · Mathematics 2023-08-29 Panchugopal Bikram , Diptesh Saha

In this paper, we consider a question of sum-keeping about a multiplicative subsemigroup and its generator subsets in a semiring, and develop some elementary (collapse) process of the sum-keeping retraction through subsets until one minimal…

Number Theory · Mathematics 2025-04-04 Derong Qiu