Stationary Values of Sectional Curvature in Grassmann Manifolds of Bivectors

In the Grassmann manifold G _2,n ⁺ of bivectors (n4), the sectional curvature K() in the direction of a 2-plane takes values in 0,2]. All stationary values a of K() such that the gradient K|₌₀ vanishes for at least one ₀ K^–1(a) are found. The values are {0,1,2} for n=4, {0,1/5,1,2} for n=5, and {0,1/5,1/2,1,2} for n6. Bibliography: 7 titles.