Consider the principal U(n) bundles over Grassmann manifolds . Given X∈Um,n(C) and a 2-dimensional subspace m′⊂m⊂u(m+n), assume either m′ is induced by X,Y∈Um,n(C) with X⁎Y=μIn for some μ∈R or by a72b96ae6c2" title="Click to view the MathML source">X,iX∈Um,n(C). Then m′ gives rise to a complete totally geodesic surface S in the base space. Furthermore, let γ be a piecewise smooth, simple closed curve on S parametrized by a75b6f26a" title="Click to view the MathML source">0≤t≤1, and be its horizontal lift on the bundle , which is immersed in . Then
depending on whether the immersed bundle is flat or not, where A(γ) is the area of the region on the surface S surrounded by γ and .