Computation of five- and six-dimensional Bieberbach groups.
Computational aspects of group extensions and their applications in topology.
Computing fundamental domains for Fuchsian groups
We exhibit an algorithm to compute a Dirichlet domain for a Fuchsian group with cofinite area. As a consequence, we compute the invariants of , including an explicit finite presentation for .
Congruence, Similarity, and Symmetries of Geometric Objects.
Congruence subgroups associated to the Monster.
Congruence subgroups of groups commensurable with of genus 0 and 1.
Constructing irreducible representations of Weyl groups.
Constructing the maximal monoids in the semigroups , and
Correction to "Two Generator Fuchsian Groups of Genus One".
Counting crystallographic groups in low dimensions.
Counting immersed surfaces in hyperbolic 3-manifolds.
Cross ratios, Anosov representations and the energy functional on Teichmüller space
We study two classes of linear representations of a surface group: Hitchin and maximal symplectic representations. We relate them to cross ratios and thus deduce that they are displacing which means that their translation lengths are roughly controlled by the translations lengths on the Cayley graph. As a consequence, we show that the mapping class group acts properly on the space of representations and that the energy functional associated to such a representation is proper. This implies the existence...
Cross ratios, surface groups, and diffeomorphisms of the circle
This article relates representations of surface groups to cross ratios. We first identify a connected component of the space of representations into PSL(n,ℝ) – known as the n-Hitchin component– to a subset of the set of cross ratios on the boundary at infinity of the group. Similarly, we study some representations into associated to cross ratios and exhibit a “character variety” of these representations. We show that this character variety contains alln-Hitchin components as well as the set of...
Crystallographic actions on Lie groups and post-Lie algebra structures
This survey on crystallographic groups, geometric structures on Lie groups and associated algebraic structures is based on a lecture given in the Ostrava research seminar in .
Cyclic parabolic quasiconformal groups that are not quasiconformal conjugates of Möbius groups.
Cyclic projective planes and Wada dessins.
Das K (..., 1)-Problem für die affinen Wurzelsysteme vom Typ An, Cn.
Das Relationenproblem für eine Klasse von Untergruppen orthogonaler Gruppen.
Decomposition of isometries of isotropic over finite fields into simple isometries
Decomposition of special Jacobi sets