Ann Kiefer

collaborators

4 papers

math.GR2018

A dichotomy for integral group rings via higher modular groups as amalgamated products

Andreas Bächle, Geoffrey Janssens, Eric Jespers +2

We show that $U (Z G)$ , the unit group of the integral group ring $Z G$ , either satisfies Kazhdan's property (T) or is, up to commensurability, a non-triv…

math.GR2018

Abelianization and fixed point properties of units in integral group rings

Andreas Bächle, Geoffrey Janssens, Eric Jespers +2

Let $G$ be a finite group and $U (Z G)$ the unit group of the integral group ring $Z G$ . We prove a unit theorem, namely a characterization of when $\ma…

math.GR2015

Presentations of Groups Acting Discontinuously on Direct Products of Hyperbolic Spaces

Eric Jespers, Ann Kiefer, Ángel del Río

The problem of describing the group of units $U (Z G)$ of the integral group ring $Z G$ of a finite group $G$ has attracted a lot of attention and provid…

math.GR2015

Revisiting Poincaré's Theorem on presentations of discontinuous groups via fundamental polyhedra

Eric Jespers, Ann Kiefer, Ángel del Río

We give a new self-contained proof of Poincaré's Polyhedron Theorem on presentations of discontinuous groups of isometries of a Riemann manifold of constant curvature. The proof is…