Representation equivalent Bieberbach groups and strongly isospectral flat manifolds

Emilio A. Lauret

Let ${\Gamma }_1$ and ${\Gamma }_2$ be Bieberbach groups contained in the full isometry group $G$ of ${\mathbb{R}}^n$. We prove that if the compact flat manifolds ${\Gamma }_1\backslash {\mathbb{R}}^n$ and $Γ_…