Curvature, Connected Sums, and Seiberg-Witten Theory

摘要

We consider several differential-topological invariants of compact4-manifolds which directly arise from Riemannian variational problems. Usingrecent results of Bauer and Furuta, we compute these invariants in many casesthat were previously intractable. In particular, we are now able to calculatethe Yamabe invariant for certain connected sums of complex surfaces.