【摘要】 设X是n维非奇异射影簇,L是X上的丰富线丛,KX是X的典范丛,f:X→Y是以KX+mL为支撑处子的双有理收缩态射(m≥1),F是f的任一纤维.文中证明了如果dimF=m+1,那么F的每个不可约分支同构于射影空间m+1或者超二次曲面m+1.更多还原

【Abstract】 Let X be a nonsingular projective variety of dimension n,L be an ample line bundle over X and KX be the canonical bundle over X.Let f:X→Y be the birational contraction from X to Y with supporting divisor KX+mL for some m≥1,F be any generic fiber of f.If dimF=m+1,then each irreducible component of F is isomorphic to projective space m+1or hyperquadric m+1.更多还原