A simple criterion for non-relative hyperbolicity and one-endedness of groups

Contracting isometries of CAT(0) cube complexes and acylindrical hyperbolicity of diagram groups

The main technical result of this paper is to characterize the contracting isometries of a CAT(0) cube complex without any assumption on its local finiteness. Afterwards, we introduce the combinatorial boundary of a CAT(0) cube complex, and we show that contracting isometries are strongly related to isolated points at infinity, when the complex is locally finite. This boundary turns out to appear naturally in the context of Guba and Sapir's diagram groups, and we apply our main criterion to determine precisely when an element of a diagram group induces a contracting isometry on the associated …

层级双曲性的组合视角及其在映射类群商群中的应用

A combinatorial take on hierarchical hyperbolicity and applications to quotients of mapping class groups

本研究提出基于双曲单纯复形作用的层级双曲群组合判据，证明映射类群模Dehn扭大幂次的商群为层级双曲群，构造非初等双曲商群并将相关有限商问题归约为特定双曲群的剩余有限性问题。

Quasiconvexity and relatively hyperbolic groups that split

We explore the combination theorem for a group G splitting as a graph of relatively hyperbolic groups. Using the fine graph approach to relative hyperbolicity, we find short proofs of the relative hyperbolicity of G under certain conditions. We then provide a criterion for the relative quasiconvexity of a subgroup H depending on the relative quasiconvexity of the intersection of H with the vertex groups of G. We give an application towards local relative quasiconvexity.

许多分层超几何空间的组合结构

A Combinatorial Structure for Many Hierarchically Hyperbolic Spaces

本文提出通过组合方法构建新的分层超几何空间，并揭示了分层超几何空间与格理论之间的联系。

Separation and Relative Quasi-convexity Criteria for Relatively Geometric Actions

Bowditch characterized relative hyperbolicity in terms of group actions on fine hyperbolic graphs with finitely many edge orbits and finite edge stabilizers. In this paper, we define generalized fine actions on hyperbolic graphs, in which the peripheral subgroups are allowed to stabilize finite sub-graphs rather than stabilizing a point. Generalized fine actions are useful for studying groups that act relatively geometrically on a CAT(0) cube complex, which were recently defined by the first two authors. Specifically, we show that a group acting relatively geometrically on a CAT(0) cube comple…