复射影直纹面（II）

On ComPlex Ruled Surfaces

本文利用几何直纹面及曲线上秩－２局部自由层的一些性质，讨论射影空间中的直纹面一些特性，给出了非正则直纹面次数的下界并讨论了个维射影空间中次数接近下界的非正则直纹面的结构，如奇点集的结构，底曲线的结构及纤维束次数等，完全确定了这类曲面的几何结构。

In this paper,we use some properties of geometric ruled surfaces and locally freesheaf of rank two to discuss some geometric characteristic of ruled surfaces in projective space. We give a lower bound of the degree of irregular ruled surfaces.We also discuss the structureof irregular surface of small degree,for example,the structure of singular locus and base curvesand so on,we have decided the structure of such surfaces completely.