Freedman's theorem

《Higher Algebra》 · 第 240 页 · Section 5.2，Freedman’s Classification Theorem（完整分类陈述）

Freedman’s Classification Theorem. For any integral symmetric unimodular form \(Q\), there is a closed simply-connected topological 4-manifold that has \(Q\) as its intersection form. If \(Q\) is even, there is exactly one such manifold. If \(Q\) is odd, there are exactly two such manifolds, at least one of which does not admit any smooth structures.