Geodesic
Stationary values of sectional curvature in Grassmanian manifolds of bivectors
Zapiski Nauchnykh Seminarov POMI, Geometry and topology. Part 4, Tome 261 (1999), pp. 102-118 
S. E. Kozlov. Stationary values of sectional curvature in Grassmanian manifolds of bivectors. Zapiski Nauchnykh Seminarov POMI, Geometry and topology. Part 4, Tome 261 (1999), pp. 102-118. http://geodesic.mathdoc.fr/item/ZNSL_1999_261_a7/
@article{ZNSL_1999_261_a7,
     author = {S. E. Kozlov},
     title = {Stationary values of sectional curvature in {Grassmanian} manifolds of bivectors},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {102--118},
     year = {1999},
     volume = {261},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1999_261_a7/}
}
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Voir la notice du chapitre de livre provenant de la source Math-Net.Ru

In the Grassmanian manifold $G^+_{2,n}$ of bivectors $(n\ge4)$ the curvature $K(\sigma)$ of the section on direction of a flat area $\sigma$ takes values on the range from 0 to 2. All stationary values $a$ of the function $K(\sigma)$ such that the gradient $\nabla K\big|_{\sigma=\sigma_0}=0$ for at least one $\sigma_0\in K^{-1}(a)$ are found. Those values are $\{0,1,2\}$ for $n=4$, $\{0,1/5,1,2\}$ for $n=5$, $\{0,1/5,1/2,1,2\}$ for $n\ge6$.