Some remarks on positively curved 4-manifolds
Let M be a closed connected 4-manifold with \(\pi_ 1(M)=0\). Assume M has positive curvature. The author studies the Weitzenböck operator on 2- forms on M to conclude that M admits at most one harmonic 2-form of constant length. If M does admit such a form, then the intersection form of M is definite.
scientific article; zbMATH DE number 4096305