This paper introduces a generalized Frenet formula for holomorphic 2-spheres S2 in Grassmann manifolds G(k,n) and gains a generalized Plu|¨cker formula. By use of these formulas a complete classification of constant curved holomorphic S2 in G(2,4) is given. Some pinching theorems for Gaussian curvature generalizes the corresponding results about holomorphic and minimal S2 in CPn-1. Einsteinian holomorphic subbundle o(?) the trivial bundle S2 × Cn is investigated.
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