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We show that the (topological) full group of a minimal pseudogroup over the Cantor set satisfies various rigidity phenomena of topological dynamical and combinatorial nature. Our main result applies to its possible homomorphisms into other…

Group Theory · Mathematics 2018-12-12 Nicolás Matte Bon

It is shown that Nichols algebras over alternating groups A_m, m>4, are infinite dimensional. This proves that any complex finite dimensional pointed Hopf algebra with group of group-likes isomorphic to A_m is isomorphic to the group…

Quantum Algebra · Mathematics 2011-04-13 N. Andruskiewitsch , F. Fantino , M. Graña , L. Vendramin

We assign a relational structure to any finite algebra in a canonical way, using solution sets of equations, and we prove that this relational structure is polymorphism-homogeneous if and only if the algebra itself is…

Logic · Mathematics 2024-02-14 Endre Tóth , Tamás Waldhauser

We give strengthened versions of the Herwig-Lascar and Hodkinson-Otto extension theorems for partial automorphisms of finite structures. Such strengthenings yield several combinatorial and group-theoretic consequences for homogeneous…

Logic · Mathematics 2019-04-17 Daoud Siniora , Sławomir Solecki

We construct a universal action of a countable locally finite group (the Hall's group) on a separable metric space by isometries. This single action contains all actions of all countable locally finite groups on all separable metric spaces…

Group Theory · Mathematics 2018-08-03 Michal Doucha

In 1959, P. Hall introduced the locally finite group $\mathcal{U}$, today known as Hall's universal group. This group is countable, universal, simple, and any two finite isomorphic subgroups are conjugate in $\mathcal{U}$. It can be…

Group Theory · Mathematics 2019-02-12 Igor Dolinka , Robert D. Gray

We classify all finite-dimensional connected Hopf algebras with large abelian primitive spaces. We show that they are Hopf algebra extensions of restricted enveloping algebras of certain restricted Lie algebras. For any abelian matched pair…

Rings and Algebras · Mathematics 2015-07-02 Xingting Wang

We show that several classes of groups G of PL-homeomorphisms of the real line admit non-trivial homomorphisms from G to the additive group of reals that are fixed by every automorphism of G. The classes of groups enjoying the stated…

Group Theory · Mathematics 2016-04-22 Daciberg L. Gonçalves , Parameswaran Sankaran , Ralph Strebel

A characterization is given of finite groups $H$ that have skew-morphisms of order coprime to the order $|H|$, and their skew-morphisms. A complete classification is then given of the automorphism groups and the underlying graphs of…

Group Theory · Mathematics 2025-10-14 Wendi Di , Zheng Guo , Cai Heng Li

Let $G$ be a residually finite, good group of finite virtual cohomological dimension. We prove that the natural monomorphism $G\hookrightarrow\hat{G}$ induces a bijective correspondence between conjugacy classes of finite $p$-subgroups of…

Group Theory · Mathematics 2024-10-29 Marco Boggi , Pavel Zalesskii

We prove that given a fixed finite tree $P$, almost all trees contain $P$ as a subtree. Moreover, the inclusion can be made so that it induces an embedding of the corresponding (quantum) automorphism groups, thereby providing generic…

Operator Algebras · Mathematics 2026-05-20 Lucas Alger , Julie Capron , Félix de la Salle

We show that the countable universal homogeneous meet-tree has a generic automorphism, but it does not have a generic pair of automorphisms.

Logic · Mathematics 2022-03-11 Itay Kaplan , Tomasz Rzepecki , Daoud Siniora

We show that the cohomology ring of a finite-dimensional complex pointed Hopf algebra with an abelian group of group-like elements is finitely generated. Our strategy has three major steps. We first reduce the problem to the finite…

Quantum Algebra · Mathematics 2021-08-03 Nicolás Andruskiewitsch , Iván Angiono , Julia Pevtsova , Sarah Witherspoon

In this paper we show that evolution algebras over any given field $\Bbbk$ are universally finite. In other words, given any finite group $G$, there exist infinitely many regular evolution algebras $X$ such that $Aut(X)\cong G$. The proof…

Rings and Algebras · Mathematics 2021-12-15 Cristina Costoya , Panagiote Ligouras , Alicia Tocino , Antonio Viruel

We prove that every 2-local automorphism of the unitary group or the general linear group on a complex infinite-dimensional separable Hilbert space is an automorphism. Thus these types of transformations are completely determined by their…

Operator Algebras · Mathematics 2007-05-23 Lajos Molnar , Peter Semrl

We show that every two-dimensional class of topological similarity, and hence every diagonal conjugacy class of pairs, is meager in the group of order preserving bijections of the rationals and in the group of automorphisms of the randomly…

Logic · Mathematics 2010-10-05 Konstantin Slutsky

We show that compact complex manifolds of algebraic dimension zero bearing a holomorphic Cartan geometry of algebraic type have infinite fundamental group. This generalizes the main Theorem in [DM] where the same result was proved for the…

Differential Geometry · Mathematics 2019-12-03 Indranil Biswas , Sorin Dumitrescu , Benjamin McKay

We prove that the Fra\"iss\'e limit of a Fra\"iss\'e class $\mathcal C$ is the (unique) countable structure whose isomorphism type is comeager (with respect to a certain logic topology) in the Baire space of all structures whose age is…

Logic · Mathematics 2021-10-15 Zakhar Kabluchko , Katrin Tent

We show how to count and randomly generate finitely generated subgroups of the modular group $\textsf{PSL}(2,\mathbb{Z})$ of a given isomorphism type. We also prove that almost malnormality and non-parabolicity are negligible properties for…

Group Theory · Mathematics 2021-03-01 Frédérique Bassino , Cyril Nicaud , Pascal Weil

This article initiates a geometric study of the automorphism groups of general graph products of groups, and investigates the algebraic and geometric structure of automorphism groups of cyclic product of groups. For a cyclic product of at…

Group Theory · Mathematics 2018-03-21 Anthony Genevois , Alexandre Martin