Uniform Exponential Growth of Polycyclic Groups

Notes on uniform exponential growth and Tits alternative

These notes contain results concerning uniform exponential growth which were obtained in collaborations with E. Breuillard and A. Salehi-Golsefidy, mostly during 2005, improving Eskin-Mozes-Oh theorem \cite{EMO}, as well as a uniform uniform version of Tits alternative improving \cite{uti}.

On uniform exponential growth for solvable groups

Using a theorem of J. Groves we give a ping-pong proof of Osin's uniform exponential growth for solvable groups. We discuss slow exponential growth and show that this phenomenon disappears as one passes to a finite index subgroup.

一个非一致指数增长的圆柱双曲群

An acylindrically hyperbolic group of non-uniform exponential growth

构造了一个具有非一致指数增长和Kazhdan性质(T)的圆柱双曲群，该群是递增有限秩自由群的自同构群的公共商。

Non proper HNN extensions and uniform uniform exponential growth

If a finitely generated torsion free group K has the property that all finitely generated subgroups S of K are either small or have growth constant bounded uniformly away from 1 then a non proper HNN extension G of K, that is a semidirect product of K by the integers, has the same property. Here small means cyclic or, if the automorphism has no periodic conjugacy classes, free abelian of bounded rank.

一个有限呈现的非均匀指数增长群

Non-uniform exponential growth and the decay of growth rates in growing dimensions

通过Thompson群V，首次构造了有限呈现群和单群中具有非均匀指数增长的例子。

双曲空间上具有正常乘积作用的群的均匀指数增长

Uniform exponential growth for groups with proper product actions on hyperbolic spaces

本文研究有限生成群在双曲空间有限乘积上的正常作用，证明在粗稠密轨道或阴影性质下非虚阿贝尔子群具有均匀指数增长，并在弱非柱状条件下给出乘积集增长的完整分类。

超限增长在小取消群中

Uniform growth in small cancellation groups

研究探讨了超限指数增长在超限小取消群中的闭包性质，证明了在超限小取消商下，此类群的闭包，并给出了超限指数增长与超限熵-基数估计的相关结论。

Uniform exponential growth for CAT(0) square complexes

In this paper we start the inquiry into proving uniform exponential growth in the context of groups acting on CAT(0) cube complexes. We address free group actions on CAT(0) square complexes and prove a more general statement. This says that if $F$ is a finite collection of hyperbolic automorphisms of a CAT(0) square complex $X$, then either there exists a pair of words of length at most 10 in $F$ which freely generate a free semigroup, or all elements of $F$ stabilize a flat (of dimension 1 or 2 in $X$). As a corollary, we obtain a lower bound for the growth constant, $\sqrt[10]{2}$, which is …

幂零群中共轭可分性增长的统一上界

Uniform Upper Bounds for Conjugacy Separability Growth in Nilpotent Groups

针对幂零群的共轭可分性增长函数，本文给出次数至多线性于幂零类、二次于Hirsch长度的显式多项式上界，并证明二步幂零情形下该界最优，同时纠正了文献错误。

Uniform Growth, Actions on Trees and $GL_2$

We use actions on trees to determine uniform exponential growth for subgroups of $GL_2$.

Uniformly exponential growth and mapping class groups of surfaces

We show that the mapping class group of an orientable finite type surface has uniformly exponential growth, as well as various closely related groups. This provides further evidence that mapping class groups may be linear.

Hierarchically hyperbolic groups and uniform exponential growth

We give several sufficient conditions for uniform exponential growth in the setting of virtually torsion-free hierarchically hyperbolic groups. For example, any hierarchically hyperbolic group that is also acylindrically hyperbolic has uniform exponential growth. In addition, we provide a quasi-isometric characterization of hierarchically hyperbolic groups without uniform exponential growth. To achieve this, we gain new insights on the structure of certain classes of hierarchically hyperbolic groups. Our methods give a new unified proof of uniform exponential growth for several examples of gro…

Extensions of hyperbolic groups have locally uniform exponential growth

We introduce a quantitative characterization of subgroup alternatives modeled on the Tits alternative in terms of group laws and investigate when this property is preserved under extensions. We develop a framework that lets us expand the classes of groups known to have locally uniform exponential growth to include extensions of either word hyperbolic or right-angled Artin groups by groups with locally uniform exponential growth. From this, we deduce that the automorphism group of a torsion-free one-ended hyperbolic group has locally uniform exponential growth. Our methods also demonstrate that…

A Wilson Group of Non-Uniformly Exponential Growth

This note constructs a finitely generated group $W$ whose word-growth is exponential, but for which the infimum of the growth rates over all finite generating sets is 1 -- in other words, of non-uniformly exponential growth. This answers a question by Mikhael Gromov. The construction also yields a group of intermediate growth $V$ that locally resembles $W$ in that (by changing the generating set of $W$) there are isomorphic balls of arbitrarily large radius in $V$ and $W$'s Cayley graphs.

作用于具有一致指数增长的 CAT(0) 立方复形的群

Groups acting on CAT(0) cube complexes with uniform exponential growth

研究作用于 CAT(0) 立方复形的群的一致指数增长，证明无全局不动点作用于方复形的群有一致指数增长或稳定欧几里得子复形，推广前人工作并应用于 Higman 群和无三角形 Artin 群子群。

Purely exponential growth of cusp-uniform actions

Suppose that a countable group $G$ admits a cusp-uniform action on a hyperbolic space $(X,d)$ such that $G$ is of divergent type. The main result of the paper is characterizing the purely exponential growth type of the orbit growth function by a condition introduced by Dal'bo-Otal-Peigné. For geometrically finite Cartan-Hadamard manifolds with pinched negative curvature this condition ensures the finiteness of Bowen-Margulis-Sullivan measures. In this case, our result recovers a theorem of Roblin (in a weaker form). Our main tool is the Patterson-Sullivan measures on the Gromov boundary of $X$…

Entropy of Bernoulli convolutions and uniform exponential growth for linear groups

The exponential growth rate of non polynomially growing subgroups of $GL_d$ is conjectured to admit a uniform lower bound. This is known for non-amenable subgroups, while for amenable subgroups it is known to imply the Lehmer conjecture from number theory. In this note, we show that it is equivalent to the Lehmer conjecture. This is done by establishing a lower bound for the entropy of the random walk on the semigroup generated by the maps $x\mapsto λ\cdot x\pm 1$, where $λ$ is an algebraic number. We give a bound in terms of the Mahler measure of $λ$. We also derive a bound on the dimension o…

A gap property for the growth of closed 3-manifold groups

We provide a lower bound for the uniform exponential growth rate of closed nonflat nonpositively curved 3-manifold groups. A detailed study of the uniform exponential growth rate of closed 3-manifold groups is also presented.

投影直线自同态的一个统一的Tits二择性

A uniform Tits alternative for endomorphisms of the projective line

本文推广了投影直线自同态半群的Tits二择性，通过扩展算术高度函数的乒乓球论证，证明了指数增长半群具有一致指数增长。