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We show that for every positive integer $n$ there exists a simple group that is of type $\mathrm{F}_{n-1}$ but not of type $\mathrm{F}_n$. For $n\ge 3$ these groups are the first known examples of this kind. They also provide infinitely…

Group Theory · Mathematics 2018-10-23 Rachel Skipper , Stefan Witzel , Matthew C. B. Zaremsky

We study the groups of automorphisms of rational algebraic surfaces that admit a relatively minimal pencil of curves of arithmetic genus one over an algebraically closed field of arbitrary characteristic. In particular, we classify such…

Algebraic Geometry · Mathematics 2021-06-25 Igor Dolgachev , Gebhard Martin

In this article we initiate research on locally compact C*-simple groups. We first show that every C*-simple group must be totally disconnected. Then we study C*-algebras and von Neumann algebras associated with certain groups acting on…

Operator Algebras · Mathematics 2016-01-25 Sven Raum

Let \Lambda be a minimal Kac-Moody group of rank 2 defined over the finite field F_q, where q = p^a with p prime. Let G be the topological Kac-Moody group obtained by completing \Lambda. An example is G=SL_2(K), where K is the field of…

Group Theory · Mathematics 2011-06-10 Inna , Capdeboscq , Anne Thomas

We study model geometries of finitely generated groups. If a finitely generated group does not contain a non-trivial finite rank free abelian commensurated subgroup, we show any model geometry is dominated by either a symmetric space of…

Group Theory · Mathematics 2024-09-06 Alex Margolis

We show that, for any number of components, the group of braids up to link-homotopy is torsion-free. This generalizes a result of Humphries up to six components, and provides an explicit solution to a question posed by Lin and addressed by…

Geometric Topology · Mathematics 2024-05-08 Emmanuel Graff

We prove the normal subgroup property for every group that acts properly and cocompactly on a two-dimensional Euclidean building: every normal subgroup has finite index or is contained in the finite kernel of the action. As a consequence,…

Group Theory · Mathematics 2026-05-08 Jean Lécureux , Stefan Witzel

We prove that there does not exist any connected topological proper loop homeomorphic to a quasi-simple Lie group and having a compact Lie group as the group topologically generated by its left translations. Moreover, any connected…

Representation Theory · Mathematics 2015-02-25 Agota Figula , Karl Strambach

We show that with few exceptions every local isometric automorphism of the group algebra $L^p(G)$ of a compact group $G$ is an isometric automorphism.

Functional Analysis · Mathematics 2007-05-23 Lajos Molnar , Borut Zalar

We present a new notion of non-positively curved groups: the collection of discrete countable groups acting (AU-)acylindrically on finite products of $\delta$-hyperbolic spaces with general type factors. Inspired by the classical theory of…

Group Theory · Mathematics 2025-12-30 Sahana Balasubramanya , Talia Fernos

We give a new proof of the fact that finite bipartite graphs cannot be axiomatized by finitely many first-order sentences among FINITE graphs. (This fact is a consequence of a general theorem proved by L. Ham and M. Jackson, and the…

Logic · Mathematics 2021-04-01 Gábor Czédli

We show that the automorphism groups of certain countable structures obtained using the Hrushovski amalgamation method are simple groups. The structures we consider are the 'uncollapsed' structures of infinite Morley rank obtained by the ab…

Logic · Mathematics 2015-09-03 David M. Evans , Zaniar Ghadernezhad , Katrin Tent

It is proven that the identity component of the group preserving the leaves of a generalized foliation is perfect. This shows that a well-known simplicity theorem on the diffeomorphism group extends to the nontransitive case.

Differential Geometry · Mathematics 2007-05-23 Stefan Haller , Tomasz Rybicki

We describe certain almost-simple algebraic supergroups over an algebraically closed field of odd or zero characteristic. In addition to supergroups with simple Lie superalgebras from Kac's theorem, we construct new supergroups whose Lie…

Rings and Algebras · Mathematics 2025-11-21 S. Bouarroudj , A. N. Zubkov

We study natural linear representations of self-similar groups over finite fields. In particular, we show that if the group is generated by a finite automaton, then obtained matrices are automatic. This shows a new relation between two…

Group Theory · Mathematics 2014-09-18 R. Grigorchuk , Y. Leonov , V. Nekrashevych , V. Sushchansky

Let $\Gamma$ be a locally finite graph, $L$ the normalized Laplacian of $\Gamma$. If $\Gamma$ is uniformy locally finite, i.e. if each vertex has no more than $d$ adjacent vertices, then the matrix of $L$ (with respect to the standard…

Combinatorics · Mathematics 2018-08-14 Vladimir Manuilov

We obtain new presentations for the imprimitive complex reflection groups of type $(de,e,r)$ and their braid groups $B(de,e,r)$ for $d,r \ge 2$. Diagrams for these presentations are proposed. The presentations have much in common with…

Group Theory · Mathematics 2015-01-27 Ruth Corran , Eon-Kyung Lee , Sang-Jin Lee

We show that smooth well formed weighted complete intersections have finite automorphism groups, with several obvious exceptions.

Algebraic Geometry · Mathematics 2020-08-13 Victor Przyjalkowski , Constantin Shramov

Article is devoted to the Examples 2 and 3 of the symplectic solvable Lie groups $R$ with some special cohomological properties, which have been constructed by Benson and Gordon. But they are not succeeded in constructing corresponding…

Differential Geometry · Mathematics 2007-05-23 V. Gorbatsevich

In \cite{Kramer11} Kramer proves for a large class of semisimple Lie groups that they admit just one locally compact $\sigma$-compact Hausdorff topology compatible with the group operations. We present two different methods of generalising…

Group Theory · Mathematics 2014-11-06 Rupert McCallum