Flip Of Small Contraction On Odd-dimensional Projective Variety

The main result of this paper is as follows : Let X be a smooth projective variety of dimension 7 which has a small contraction map f:X→Y. Assume that all uniruled components E_i of the exceptional locus E of f are smooth subvarieties and have the dimension 4 , and the normal bundle N_E1/x(?)O_E1(-1) , then E_i(?)p⁴ or Q⁴, where p⁴ is the complex projective space of dimension 4, Q⁴ is a hyperquadric surface in p⁵. Moreover, the flip f⁺:X→Y of the small contraction f exists.