The non-amenability of Schreier graphs for infinite index quasiconvex subgroups of hyperbolic groups

Amenability of Schreier graphs and strongly generic algorithms for the conjugacy problem

In various occasions the conjugacy problem in finitely generated amalgamated products and HNN extensions can be decided efficiently for elements which cannot be conjugated into the base groups. This observation asks for a bound on how many such elements there are. Such bounds can be derived using the theory of amenable graphs: In this work we examine Schreier graphs of amalgamated products and HNN extensions. For an amalgamated product $G = H *_A K $ with $[H:A] \geq [K:A] \geq 2$, the Schreier graph with respect to $H$ or $K$ turns out to be non-amenable if and only if $[H:A] \geq 3$. Moreove…

判定双曲群是否沿给定拟凸子群分裂

Deciding if a hyperbolic group splits over a given quasiconvex subgroup

本文提出判定双曲群沿给定拟凸子群是否分裂的算法，并扩展至计算过滤端数与Schreier图端数，利用带标号有向图编码边界连通性信息。

Amenability of Bounded Automata Groups on Infinite Alphabets

We study the action of groups generated by bounded activity automata with infinite alphabets on their orbital Schreier graphs. We introduce an amenability criterion for such groups based on the recurrence of the first level action. This criterion is a natural extension of the result that all groups generated by bounded activity automata with finite alphabets are amenable. Our motivation comes from the investigation of iterated monodromy groups of entire functions.

二次自动群的可 amenability

Amenability of quadratic automaton groups

研究二次活动自动群的可 amenability，通过Schreier图的电导下界结合JNS结果证明其可 amenability，提出新的加权Nash-Williams准则。

The geometry of relative Cayley graphs for subgroups of hyperbolic groups

We show that if H is a quasiconvex subgroup of a hyperbolic group G then the relative Cayley graph Y (also known as the Schreier coset graph) for G/H is Gromov-hyperbolic. We also observe that in this situation if G is torsion-free and non-elementary and H has infinite index in G then the simple random walk on Y is transient.

Extensions of amenable groups by recurrent groupoids

We show that amenability of a group acting by homeomorphisms can be deduced from a certain local property of the action and recurrency of the orbital Schreier graphs. This covers amenability of a wide class groups, the amenability of which was an open problem, as well as unifies many known examples to one general proof. In particular, this includes Grigorchuk's group, Basilica group, the full topological group of Cantor minimal system, groups acting on rooted trees by bounded automorphisms, groups generated by finite automata of linear activity growth, groups that naturally appear in holomorph…