Geometrically simply connected 4-manifolds and stable cohomotopy Seiberg-Witten invariants

We show that every positive definite closed 4-manifold with $b_2^{+}>1$ and without 1-handles has a vanishing stable cohomotopy Seiberg-Witten invariant, and thus admits no symplectic structure. We also show that every closed oriented 4-manifold with $b_2^{+}\equiv ̸1$ and $b_2^{-}\equiv ̸1(\mathrm{m}\mathrm{o}\mathrm{d}4)$ and without 1-handles admits no symplectic structure for at least one orientation of the manifold. In fact, relaxing the 1-handle condition, we prove these results under more general conditions which are much easier to verify.