2 problems

Let $G$ be a 3D space group, and consider the standard Lyndon–Hochschild–Serre spectral sequence for its translation extension. At the $E_2$ page, examine the module structures in…

Let $G$ be a 3D space group and consider its mod-2 cohomology ring $H^*(G,\mathbb{Z}_2)$. Upper-degree conjecture for generators and relations. An independent generator can appear…