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  1. Topology and Dynamics
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  5. 2024

Geometric Group Theory

‟Incoherence for right-angled Coxeter groups on surfaces” by Lorenzo Ruffoni <lorenzo.ruffoni2@gmail.com>, Binghamton University (SUNY)

Abstract:

A group is “coherent” if every finitely generated subgroup is finitely presented. In a certain sense, coherence is a low-dimensional phenomenon. For instance, 3-manifold groups and one-relator groups are coherent. In this talk we consider Coxeter groups defined by a graph that is a flag triangulation of a surface of genus g. For each g>0, we construct a Coxeter group that is right-angled, hyperbolic, and incoherent. In these examples the witness to incoherence is always the fiber in a virtual algebraic fibration. This provides positive evidence towards a variation on Singer’s Conjecture for right-angled Coxeter groups proposed by Davis-Okun. This is joint work with G. Walsh.