Energy gap for Yang-Mills connections, I: Four-dimensional closed Riemannian manifolds

We extend an L2 energy gap result due to Min-Oo [28, Theorem 2] and Parker [30, Proposition 2.2] for Yang-Mills connections on principal G-bundles, P, over closed, connected, four-dimensional, oriented, smooth manifolds, X, from the case of positive Riemannian metrics to the more general case of good Riemannian metrics, including metrics that are generic and where the topologies of P and X obey certain mild conditions and the compact Lie group, G, is SU(2) or SO(3).