【摘要】 设X是n维射影流形,L是X上的丰富线丛.г=u/v是L的nef值.如果X的第二Betti数为1,那么X是指数为u的Fano流形;如果u=n+1,那么X是Pn;如果u=n,那么X是Qn或一条光滑曲线上的Pn-1丛.更多还原

【Abstract】 Let X be a n-dimensional projective manifold and L be an ample line bundle over X.г=u/v is the nef value of L.If the second Betti number of X is one,then X is a Fano manifold of index one;If u=n+1,then X is Pn;If u=n,X is either Qn,or a Pn-1-bundle over a smooth curve.更多还原