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We show that stable commutator length is rational on free products of free Abelian groups amalgamated over $\mathbb{Z}^k$, a class of groups containing the fundamental groups of all torus knot complements. We consider a geometric model for…

Group Theory · Mathematics 2014-05-13 Timothy Susse

In the 1980's K.S. Brown proved that the Houghton group $H_n$ is of type $\operatorname{F}_{n-1}$ but not $\operatorname{FP}_n$. We show that, provided $n\ge3$, the same conclusion holds for all subgroups $G$ of $H_n$ that are 'large' in…

Group Theory · Mathematics 2026-01-27 Charles Cox , Peter Kropholler , Armando Martino

In this paper we create many examples of hyperbolic groups with subgroups satisfying interesting finiteness properties. We give the first examples of subgroups of hyperbolic groups which are of type $FP_2$ but not finitely presented. We…

Group Theory · Mathematics 2021-01-08 Robert Kropholler , Federico Vigolo

We study the free objects in the variety of semigroups and variety of monoids generated by the monoid of all $n \times n$ upper triangular matrices over a commutative semiring. We obtain explicit representations of these, as multiplicative…

Rings and Algebras · Mathematics 2019-04-15 Mark Kambites

We give formulas for the numbers of type II and type IV hyperbolic components in the space of quadratic rational maps, for all fixed periods of attractive cycles.

Dynamical Systems · Mathematics 2014-02-26 Jan Kiwi , Mary Rees

We adapt Safin's result on powers of sets in free groups to obtain Helfgott type growth in free products: if A is any finite subset of a free product of two arbitrary groups then either A is conjugate into one of the factors, or the size of…

Group Theory · Mathematics 2011-09-28 J. O. Button

By representing the field content as well as the particle creation operators in terms of fermionic Fock operators, we compute the corresponding matrix elements of the Federbush model. Only when these matrix elements satisfy the form factor…

High Energy Physics - Theory · Physics 2009-11-07 Olalla Castro-Alvaredo , Andreas Fring

These notes are the English version of the paper "Hyperbolicit\'e du graphe des rayons et quasi-morphismes sur un gros groupe modulaire". The mapping class group Gamma of the complement of a Cantor set in the plane arises naturally in…

Geometric Topology · Mathematics 2018-02-09 Juliette Bavard

For any finitely generated, non-elementary, torsion-free group $G$ that is hyperbolic relative to $\mathbb P$, we show that there exists a group $G^*$ containing $G$ such that $G^*$ is hyperbolic relative to $\mathbb P$ and $G$ is not…

Group Theory · Mathematics 2012-11-13 Hadi Bigdely

Given a finitely generated subgroup $\Gamma \le \mathrm{Out}(\mathbb{F})$ of the outer automorphism group of the rank $r$ free group $\mathbb{F} = F_r$, there is a corresponding free group extension $1 \to \mathbb{F} \to E_{\Gamma} \to…

Geometric Topology · Mathematics 2018-03-16 Spencer Dowdall , Samuel J. Taylor

We give an alternative proof to Agol's classification of parabolic generating pairs of non-free Kleinian groups generated by two parabolic transformations. As an application, we give a complete characterisation of epimorphims between…

Geometric Topology · Mathematics 2020-08-05 Shunsuke Aimi , Donghi Lee , Shunsuke Sakai , Makoto Sakuma

This paper is an attempt to find out which properties of a finite group G can be expressed in terms of commutators of elements of coprime orders. A criterion of solubility of G in terms of such commutators is obtained. We also conjecture…

Group Theory · Mathematics 2012-08-17 Pavel Shumyatsky

We study the combinatorics of the contributions to the form factor of the group U(N) in the large $N$ limit. This relates to questions about semiclassical contributions to the form factor of quantum systems described by the unitary…

Condensed Matter · Physics 2007-05-23 Mirko Degli Esposti , Andreas Knauf

We present a simple method to count the number of hadronic form factors based on the partial wave formalism and crossing symmetry. In particular, we show that the number of independent nucleon form factors of spin-n, twist-2 operators (the…

High Energy Physics - Phenomenology · Physics 2009-10-31 Xiangdong Ji , Richard F. Lebed

For each group G which decomposes into a finitary direct product of free groups of finite rank we construct a regular band B such that the free idempotent generated semigroup over B contains a maximal subgroup isomorphic to G. In…

Group Theory · Mathematics 2013-03-26 Igor Dolinka

In this expository note, we illustrate phenomena and conjectures about boundaries of hyperbolic groups by considering the special cases of certain amalgams of hyperbolic groups. While doing so, we describe fundamental results on hyperbolic…

Geometric Topology · Mathematics 2019-07-17 Sang-hyun Kim , Genevieve S. Walsh

If $G_1$ and $G_2$ are torsion-free hyperbolic groups and $P<G_1\times G_2$ is a finitely generated subdirect product, then the conjugacy problem in $P$ is solvable if and only if there is a uniform algorithm to decide membership of the…

Group Theory · Mathematics 2026-04-14 Martin R. Bridson

Given a group $G = H_1 \ast_A H_2$ which is the free product of two finitely generated groups $H_1$ and $H_2$ with amalgamation over a cyclic subgroup $A$ which is malnormal in $G$, we study relations between the structure of its subgroups…

Group Theory · Mathematics 2026-03-18 Martin Kreuzer , Anja Moldenhauer , Gerhard Rosenberger

We generalize some results of Paulin and Rips-Sela on endomorphisms of hyperbolic groups to relatively hyperbolic groups, and in particular prove the following. (1) If G is a finitely generated non-elementary relatively hyperbolic group…

Group Theory · Mathematics 2011-11-10 Igor Belegradek , Andrzej Szczepanski , Oleg V. Belegradek

Let $G$ be a Lie group, with an invariant non-degenerate symmetric bilinear form on its Lie algebra, let $\pi$ be the fundamental group of an orientable (real) surface $M$ with a finite number of punctures, and let $\bold C$ be a family of…

dg-ga · Mathematics 2008-02-03 K. Guruprasad , J. Huebschmann , L. Jeffrey , A. Weinstein