Neumann eigenvalue estimate on a compact Riemannian manifold
Neumann eigenvalue estimate on a compact Riemannian manifold
In their article, P. Li and S. T. Yau give a lower bound of the first Neumann eigenvalue in terms of geometrical invariants for a compact Riemannian manifold with convex boundary. The purpose of this paper is to generalize their result to a compact Riemannian manifold with possibly nonconvex boundary.