On the cohomology ring and upper characteristic rank of Grassmannian of oriented $3$-planes

Abstract

In this paper we study the mod $2$ cohomology ring of the Grasmannian $\widetilde{G}_{n,3}$ of oriented $3$-planes in $\mathbb{R}^n$. We determine the degrees of the indecomposable elements in the cohomology ring. We also obtain an almost complete description of the cohomology ring. This partial description allows us to provide lower and upper bounds on the cup length of $\widetilde{G}_{n,3}$. As another application, we show that the upper characteristic rank of $\widetilde{G}_{n,3}$ equals the characteristic rank of $\widetilde{\gamma}_{n,3}$, the oriented tautological bundle over $\widetilde{G}_{n,3}$.