Nilpotency degree of cohomology rings in characteristic p
Pham Anh Minh

Abstract.
Let $p$ be an odd prime number. The purpose of this paper is to provide
a $p$-group $\mathcal G$ whose mod-$p$ cohomology ring has a nilpotent
element $\xi \in H^(\mathcal G)$ satisfying $\xi^p \ne 0$.