Nonexistence of complete metrics with uniformly positive scalar curvature

Abstract

Let $X$ be a connected oriented even-dimensional manifold whose universal cover is spin. We prove that $X$ admits no complete metric with uniformly positive scalar curvature when either infinite relative $K$-area or a relative cohomological condition holds along compact sets escaping to infinity in a fixed open subset with compact complement. The proof compares twisted Dirac operators on spin covers of compact manifolds with boundary and combines a heat-kernel argument on fundamental domains with a long-neck estimate.