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We prove that uniformly locally finite metric spaces with isomorphic Roe algebras must be coarsely equivalent. As an application, we also prove that the outer automorphism group of the Roe algebra of a metric space of bounded geometry is…

Operator Algebras · Mathematics 2025-03-10 Diego Martínez , Federico Vigolo

We show that if $G$ is a finite group whose Sylow $2$-subgroups are wreathed, then the intersection $\Outc(G) \cap \OutCol(G)$ has odd order, where $\Outc(G)$ and $\OutCol(G)$ denote the class-preserving and Coleman outer automorphism…

Group Theory · Mathematics 2026-03-16 Riccardo Aragona

We continue our study of the outer Pinsker factor for probability measure-preserving actions of sofic groups. Using the notion of doubly quenched convergence developed by Austin, we prove that in many cases the outer Pinsker factor of a…

Dynamical Systems · Mathematics 2021-03-26 Ben Hayes

We investigate the structure of the outer automorphism group of the Cuntz algebra and the closely related problem of conjugacy of MASAa in O_n. In particular, we exhibit an uncountable family of MASAs, conjugate to the standard MASA D_n via…

Operator Algebras · Mathematics 2015-10-20 Roberto Conti , Jeong Hee Hong , Wojciech Szymanski

Let $k$ be an algebraically-closed field, and $B$ a unital, associative $k$-algebra with $n := \dim_kB < \infty$. For each $1 \le m \le n$, the collection of all $m$-dimensional subalgebras of $B$ carries the structure of a projective…

Rings and Algebras · Mathematics 2019-02-25 Alexander H. Sistko

We investigate the general structure of the automorphism group and the Lie algebra of derivations of a finitely generated vertex operator algebra. The automorphism group is isomorphic to an algebraic group. Under natural assumptions, the…

Quantum Algebra · Mathematics 2007-05-23 C. Dong , R. L. Griess

Toral automorphisms are widely used (discrete) dynamical systems, the perhaps most prominent example (in 2D) being Arnold's cat map. Given such an automorphism M, its symmetries (i.e. all automorphisms that commute with M) and reversing…

Dynamical Systems · Mathematics 2007-05-23 Michael Baake

It is known that there are specific examples of ergodic transformations on measure spaces for which the calculation of the outer measure of transformation invariant sets leads to a condition closely resembling Carath\'eodory's condition for…

Functional Analysis · Mathematics 2011-01-11 Amos N. Koeller

In this paper, we study some properties of the outer automorphism group of free Burnside groups of large odd exponent. In particular, we prove that it contains free and free abelian subgroups.

Group Theory · Mathematics 2016-06-03 Rémi Coulon

In this note, we compute the group of automorphisms of Projective, Affine and Euclidean Geometries in the sense of Klein. As an application, we give a simple construction of the outer automorphism of S_6.

Group Theory · Mathematics 2013-07-05 Alberto Navarro , Jose Navarro

In the present paper, we study the outer automorphism groups of the absolute Galois groups of 2-adic local fields from the point of view of anabelian geometry. Let us recall that it is well-known that the natural homomorphism from the…

Number Theory · Mathematics 2025-12-05 Yu Nishio

Let $A$ be a separable, unital, simple, $\mathcal{Z}$-stable, nuclear $C^*$-algebra, and let $\alpha\colon G\to \mathrm{Aut}(A)$ be an action of a countable amenable group $G$. If the trace space $T(A)$ is a Bauer simplex and the action of…

Operator Algebras · Mathematics 2020-03-06 Eusebio Gardella , Ilan Hirshberg

In this paper we prove that every automorphism of the semigroup of invertible matrices with nonnegative elements over a linearly oredered associative ring on some specially defined subgroup concides with the composition of an inner…

Rings and Algebras · Mathematics 2007-05-23 Elena I. Bunina , Alexandr V. Mikhalev

Let $M^{r}$ be a connected orientable manifold with the Euler characteristic $\chi(M)\not \equiv 0\operatorname{mod}6$. Denote by $\mathrm{SAut}(F_{n})$ the unique subgroup of index two in the automorphism group of a free group. Then any…

Algebraic Topology · Mathematics 2018-03-16 Shengkui Ye

In this paper, we briefly review some of the known results concerning the cohomological structures of the mapping class group of surfaces, the outer automorphism group of free groups, the diffeomorphism group of surfaces as well as various…

Geometric Topology · Mathematics 2007-05-23 Shigeyuki Morita

Let $\Lambda$ be a countably infinite property (T) group, and let $D$ be UHF-algebra of infinite type. We prove that there exists a continuum of pairwise non (weakly) cocycle conjugate, strongly outer actions of $\Lambda$ on $D$. The proof…

Operator Algebras · Mathematics 2017-12-20 Eusebio Gardella , Martino Lupini

We construct the first examples of genuine ergodic discrete measured groupoids that are not isomorphic to any equivalence relation or transformation groupoid. We use a construction due to B.H. Neumann of an uncountable family of pairwise…

Group Theory · Mathematics 2025-10-15 Soham Chakraborty

Local mean and individual (with respect to almost uniform convergence in Egorov's sense) ergodic theorems are established for actions of the semigroup $\mathbb R_+^d$ in symmetric spaces of measurable operators associated with a semifinite…

Functional Analysis · Mathematics 2018-05-08 Vladimir Chilin , Semyon Litvinov

For every free product decomposition $G = G_{1} \ast ...\ast G_{q} \ast F_{r}$ of a group of finite Kurosh rank $G$, where $F_r$ is a finitely generated free group, we can associate some (relative) outer space $\mathcal{O}$. We study the…

Group Theory · Mathematics 2015-11-21 Dionysios Syrigos

If an outer (multilinear) commutator identity holds in a large subgroup of a group, then it holds also in a large characteristic subgroup. Similar assertions are valid for algebras and their ideals or subspaces. Varying the meaning of the…

Group Theory · Mathematics 2010-09-01 Evgenii I. Khukhro , Anton A. Klyachko , Natalia Yu. Makarenko , Yulia B. Melnikova
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