On the degeneration of harmonic sequences from surfaces into complex Grassmann manifolds

summary:Let $f:M\rightarrow G(m,n)$ be a harmonic map from surface into complex Grassmann manifold. In this paper, some sufficient conditions for the harmonic sequence generated by $f$ to have degenerate $\partial ^{\prime }$-transform or $\partial ^{\prime \prime }$-transform are given