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We define a notion of relative soficity for countable groups with respect to a family of groups. A group is sofic if and only if it is relative sofic with respect to the family consisting only of the trivial group. If a group is relatively…

Group Theory · Mathematics 2019-01-11 Ronghui Ji , Crichton Ogle , Bobby Ramsey

Let K be a discretly henselian field whose residue field is separably closed. Answering a question raised by G. Prasad, we show that a semisimple K-- group G is quasi-split if and only if it quasi--splits after a finite tamely ramified…

Group Theory · Mathematics 2017-07-12 Philippe Gille

The class, denoted by $\mathscr{S}$, of totally disconnected locally compact groups which are non-discrete, compactly generated, and topologically simple contains many compelling examples. In recent years, a general theory for these groups,…

Group Theory · Mathematics 2022-01-17 Pierre-Emmanuel Caprace , Colin D. Reid , Phillip Wesolek

We say that a finite metric space $X$ can be embedded almost isometrically into a class of metric spaces $C$, if for every $\epsilon > 0$ there exists an embedding of $X$ into one of the elements of $C$ with the bi-Lipschitz distortion less…

Metric Geometry · Mathematics 2019-08-15 Vladimir Zolotov

We exhibit a family of infinite, finitely-presented, nilpotent-by-abelian groups. Each member of this family is a solvable S-arithmetic group that is related to Baumslag-Solitar groups, and everyone of these groups has a quasi-isometry…

Group Theory · Mathematics 2007-05-23 Kevin Wortman

The class of elementary totally disconnected groups is the smallest class of totally disconnected, locally compact, second countable groups which contains all discrete countable groups, all metrizable pro-finite groups, and is closed under…

Group Theory · Mathematics 2016-12-28 Helge Glockner

Let $G$ be a connected Lie group, $C$ be the maximal compact connected subgroup of the center of $G$, and let Aut$(G)$ denote the group of Lie automorphisms of $G$, viewed, canonically, also as a subgroup of GL$(\frak G)$, where $\frak G$…

Group Theory · Mathematics 2025-04-29 S. G. Dani , Riddhi Shah

In our previous work, we introduced a special type of Hermitian metrics called {\em torsion-critical,} which are non-K\"ahler critical points of the $L^2$-norm of Chern torsion over the space of all Hermitian metrics with unit volume on a…

Differential Geometry · Mathematics 2025-04-09 Dongmei Zhang , Fangyang Zheng

Closed subgroups of the group of isometries of the regular tree $\treeq$ that fix an end of the tree and are vertex-transitive are shown to correspond, on one hand, to self-replicating groups acting on rooted trees and, on the other hand,…

Group Theory · Mathematics 2024-10-01 George A. Willis

In this paper we classify the reducible representations of compact simple Lie groups all of whose orbits are tautly embedded in Euclidean space with respect to Z_2 coefficients.

Differential Geometry · Mathematics 2007-05-23 Claudio Gorodski

If P is an algebraic point on a commutative group scheme A/K, then P is _almost_rational_ if no two non-trivial Galois conjugates sigma(P), tau(P), have sum equal to 2P. In this paper, we classify almost rational torsion points on…

Number Theory · Mathematics 2007-05-23 Frank Calegari

Topologically and geometrically engaging actions have proved to be useful to obtain rigidity results for semisimple Lie group actions. We show that the action of a simple noncompact Lie group on a compact manifold preserving a unimodular…

Differential Geometry · Mathematics 2012-01-12 A. Candel , R. Quiroga-Barranco

We give a "limit-free formula" simplifying the computation of the topological entropy for topological automorphisms of totally disconnected locally compact groups. This result allows us to extend several basic properties of the topological…

General Topology · Mathematics 2014-01-16 Anna Giordano Bruno

We give new characterizations of sofic groups: -- A group $G$ is sofic if and only if it is a subgroup of a quotient of a direct product of alternating or symmetric groups. -- A group $G$ is sofic if and only if any system of equations…

Group Theory · Mathematics 2017-01-19 Lev Glebsky

Every locally compact local group is locally isomorphic to a topological group.

Differential Geometry · Mathematics 2010-03-05 Lou van den Dries , Isaac Goldbring

Without assuming the field structure on the additive group of real numbers $\mathbb{R}$ with the usual order $<,$ we explore the fact that every proper subgroup of $\mathbb{R}$ is either closed or dense. This property of subgroups of the…

Number Theory · Mathematics 2014-05-21 Jitender Singh

We give a complete characterization of connected Lie groups with the Approximation Property for groups (AP). To this end, we introduce a strengthening of property (T), that we call property (T*), which is a natural obstruction to the AP. In…

Group Theory · Mathematics 2022-03-31 Uffe Haagerup , Søren Knudby , Tim de Laat

We describe the structure of ``K-approximate subgroups'' of torsion-free nilpotent groups, paying particular attention to Lie groups. Three other works, by Fisher-Katz-Peng, Sanders and Tao, have appeared which independently address related…

Combinatorics · Mathematics 2009-06-22 Emmanuel Breuillard , Ben Green

A topological group is said to be ambitable if each uniformly bounded uniformly equicontinuous set of functions on the group with its right uniformity is contained in an ambit. For n=0,1,2,..., every locally aleph_n bounded topological…

Functional Analysis · Mathematics 2009-07-15 Jan Pachl

We study left-invariant generalized K\"ahler structures on almost abelian Lie groups, i.e., on solvable Lie groups with a codimension-one abelian normal subgroup. In particular, we classify six-dimensional almost abelian Lie groups which…

Differential Geometry · Mathematics 2021-02-09 Anna Fino , Fabio Paradiso