Crystallographic groups with trivial center and outer automorphism group

Rafał Lutowski, Andrzej Szczepański

Let $\Gamma$ be a crystallographic group of dimension $n,$ i.e. a discrete, cocompact subgroup of $\mathrm{Isom}({\mathbb{R}}^n)$ = $O(n)⋉{\mathbb{R}}^n.$ For any $n\ge 2,$ we…