Аннотация:
A unified method is given for describing $3$-orbifolds and $3$-manifolds in terms of a projective interpretation of Thurston geometries. As an application, a new characterization is given for Nil-orbifolds and manifolds arising as fiber spaces over Euclidean $2$-orbifolds with prescribed fundamental groups. (Theorems 3.1–3.2, see also Figure 1).
Ключевые слова:projective spheres, Thurston geometries, Nil-orbifolds and manifolds.