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We use geometric techniques to investigate several examples of quasi-isometrically embedded subgroups of Thompson's group F. Many of these are explored using the metric properties of the shift map phi in F. These subgroups have simple…

Group Theory · Mathematics 2018-03-19 Sean Cleary , Jennifer Taback

This article is dedicated to the study of asymptotically rigid mapping class groups of infinitely-punctured surfaces obtained by thickening planar trees. Such groups include the braided Ptolemy-Thompson groups $T^\sharp,T^\ast$ introduced…

Group Theory · Mathematics 2022-08-17 Anthony Genevois , Anne Lonjou , Christian Urech

We establish new results on the weak containment of quasi-regular and Koopman representations of a second countable locally compact group $G$ associated with non-singular $G$-spaces. We deduce that any two boundary representations of a…

Group Theory · Mathematics 2022-02-15 Pierre-Emmanuel Caprace , Mehrdad Kalantar , Nicolas Monod

In this paper, we present a notion of quasiconvexity in the setting of finitely-generated groups with hyperbolically embedded subgroups. Our main result shows that this notion yields uniform quasiconvex constants in the setting of coned-off…

Group Theory · Mathematics 2025-10-06 Ping Wan

In this paper we provide a framework for the study of isoperimetric problems in finitely generated group, through a combinatorial study of universal covers of compact simplicial complexes. We show that, when estimating filling functions,…

Geometric Topology · Mathematics 2015-07-07 Jason Behrstock , Cornelia Drutu

We construct holomorphic loop groups and their associated affine Kac-Moody groups and prove that they are tame Fr\'echet manifolds. These results form the functional analytic basis for the theory of affine Kac-Moody symmetric spaces,…

Functional Analysis · Mathematics 2013-05-21 Walter Freyn

We define basic notions in the category of conic representations of a topological group and prove elementary facts about them. We show that a conic representation determines an ordinary dynamical system of the group together with a…

Dynamical Systems · Mathematics 2019-03-25 Matan Tal

We introduce Cayley posets as posets arising naturally from pairs $S<T$ of semigroups, much in the same way that Cayley graph arises from a (semi)group and a subset. We show that Cayley posets are a common generalization of several known…

Combinatorics · Mathematics 2019-08-27 Ignacio García-Marco , Kolja Knauer , Guillaume Mercui-Voyant

Following T.-J. Li, W. Zhang [Comparing tamed and compatible symplectic cones and cohomological properties of almost complex manifolds, Comm. Anal. Geom.], we continue to study the link between the cohomology of an almost-complex manifold…

Differential Geometry · Mathematics 2012-11-28 Daniele Angella , Adriano Tomassini

We prove a criterion for the geometric and algebraic finiteness properties of vertex stabilisers of $G$-CW-complexes, given the finiteness properties of the group $G$ and of the stabilisers of positive dimensional cells. This generalises a…

Group Theory · Mathematics 2025-02-21 Kevin Li , Luis Jorge Sánchez Saldaña

The groups QF, QT, and QV are groups of quasi-automorphisms of the infinite binary tree. Their names indicate a similarity with Thompson's well-known groups F, T, and V. We will use the theory of diagram groups over semigroup presentations…

Group Theory · Mathematics 2018-05-02 Samuel Audino , Delaney R. Aydel , Daniel S. Farley

We study the group Tame(SL$_2$) of tame automorphisms of a smooth affine 3-dimensional quadric, which we can view as the underlying variety of SL(2,$\mathbb{C}$). We construct a square complex on which the group admits a natural cocompact…

Group Theory · Mathematics 2018-05-16 Cinzia Bisi , Jean-Philippe Furter , Stéphane Lamy

We call a symplectic rational surface $(X,\omega)$ \textit{positive} if $c_1(X)\cdot[\omega]>0$. The positivity condition of a rational surface is equivalent to the existence of a divisor $D\subset X$, such that $(X, D)$ is a log Calabi-Yau…

Symplectic Geometry · Mathematics 2022-12-06 Jun Li , Tian-Jun Li , Weiwei Wu

An almost abelian Lie group is a solvable Lie group with a codimension-one normal abelian subgroup. We characterize almost Hermitian structures on almost abelian Lie groups where the almost complex structure is harmonic with respect to the…

Differential Geometry · Mathematics 2024-08-15 Adrián Andrada , Alejandro Tolcachier

Motivated by Rosenthal's famous $l^1$-dichotomy in Banach spaces, Haydon's theorem, and additionally by recent works on tame dynamical systems, we introduce the class of tame locally convex spaces. This is a natural locally convex analogue…

Functional Analysis · Mathematics 2022-04-18 Matan Komisarchik , Michael Megrelishvili

We provide new examples of groups without rational cross-sections (also called regular normal forms), using connections with bounded generation and rational orders on groups. Specifically, our examples are extensions of infinite torsion…

Group Theory · Mathematics 2024-06-10 Corentin Bodart

We study nearly-Kahler 6-manifolds equipped with a cohomogeneity-two Lie group action for which the principal orbits are coisotropic. If the metric is complete, then we show that this last condition is automatically satisfied, and both the…

Differential Geometry · Mathematics 2018-10-31 Jesse Madnick

Let M be a six dimensional manifold, endowed with a cohomogeneity one action of G= SU_2 x SU_2, and M_reg its subset of regular points. We show that M_reg admits a smooth, 2-parameter family of G-invariant, non-isometric strict nearly…

Differential Geometry · Mathematics 2010-11-23 Andrea Spiro , Fabio Podesta'

Self-similar groups provide a rich source of groups with interesting properties; e.g., infinite torsion groups (Burnside groups) and groups with an intermediate word growth. Various self-similar groups can be described by a recursive…

Group Theory · Mathematics 2012-04-20 René Hartung

The tame flows are ``nice'' flows on ``nice'' spaces. The nice (tame) sets are the pfaffian sets introduced by Khovanski, and a flow $\Phi: \mathbb{R}\times X\to X$ on pfaffian set $X$ is tame if the graph of $\Phi$ is a pfaffian subset of…

Geometric Topology · Mathematics 2007-05-23 Liviu I. Nicolaescu