Intersection forms of non-spin four manifolds

  title={Intersection forms of non-spin four manifolds},
  author={Ronnie Lee and Tian-jun Li},
  journal={Mathematische Annalen},
1 IntroductionIt remains a central question in four manifold topology which quadratic formoccurs as the intersection form of an orientable four manifold. In the topologicalcategory, there is a beautiful answer. The celebrated result of Freedman assertsthat all the quadratic forms can be realized. However, in the smooth category, wehave a rather different picture. By the surprising result of Donaldson ([D], [FS],[A]), among the definite quadratic forms, only the diagonalizable ones can berealized… CONTINUE READING