Published online by Cambridge University Press: 20 November 2018
We consider a complete noncompact Riemannian manifold $M$ and give conditions on a compact submanifold $K\,\subset \,M$ so that the outward normal exponential map off the boundary of $K$ is a diffeomorphism onto $M\backslash K$. We use this to compactify $M$ and show that pinched negative sectional curvature outside $K$ implies $M$ has a compactification with a well-defined Hölder structure independent of $K$. The Hölder constant depends on the ratio of the curvature pinching. This extends and generalizes a 1985 result of Anderson and Schoen.