Minimal two-spheres in G(2, 4)

Abstract

In this paper, we mainly study the geometry of conformal minimal immersions of two-spheres in a complex Grassmann manifold G(2,4). At first, we give a precise description of any non-±holomorphic harmonic 2-sphere in G(2,4) with the linearly full holomorphic maps (called its directrix curve) and then, it is proved that such a conformal minimal immersion ϕ: S² → G(2, 4) with constant curvature has constant Kähler angle. Furthermore, ϕ is either , which is totally geodesic, with constant Gauss curvature 2/5 and constant Kähler angle given by t = 3/2 or , which is totally real, but it is not totally geodesic, with constant Gauss curvature 2/3, where V0, V1, V2, is the Veronese sequence.

Key words： Harmonic map; conformal minimal immersion; Gauss curvature; Kähler angle; complex Grassmann manifold