3-manifolds with nonnegative Ricci curvature (Q368623)

The author gives the full classification of 3-dimensional complete Riemannian manifolds \(M\) with non-negative Ricci curvature using the well-known result of Schoen-Yau on stable minimal surfaces in \(M\). The classification gives that either \(M\) is diffeomorphic with \(\mathbb R^3\) or the universal cover of \(M\) splits as \(N\times\mathbb R\), where \(N\) is a complete surface with non-negative sectional curvature. This result confirms Milnor's conjecture in dimension 3.