2024/07/09 by Balacheff, Florent, Sardà, Teo Gil Moreno de Mora, Sabourau, Stéphane · 2 citations
#Differential Geometry (math.DG) #FOS: Mathematics #Primary 53C23 #Secondary 53C21
paper · doi:10.48550/arxiv.2407.07198
We prove that if an orientable 3-manifold M admits a complete Riemannian metric whose scalar curvature is positive and has a subquadratic decay at infinity, then it decomposes as a (possibly infinite) connected sum of spherical manifolds and \mathbbS2 × \mathbbS1 summands. This generalises a theorem of Gromov and Wang by using a different, more topological, approach. As a result, the manifold M carries a complete Riemannian metric of uniformly positive scalar curvature, which partially answers a conjecture of Gromov. More generally, the topological decomposition holds without any scalar curvature assumption under a weaker condition on the filling discs of closed curves in the universal cover based on the notion of fill radius. Moreover, the decay rate of the scalar curvature is optimal in this decomposition theorem. Indeed, the manifold ℝ2 × \mathbbS1 supports a complete metric of positive scalar curvature with exactly quadratic decay, but does not admit a decomposition as a connected sum.