For 10 points, name this concept from mathematics which is roughly stated as the outer edge or the division between in the space and outside of it.
Lefschetz duality is used when a manifold has one of these structures. Homology groups are the kernel of an one operator named for this modded by the image of another. The Gauss-Bonnet theorem relates the Gaussian curvature of a manifold to the geodesic curvature of this structure. Sturm-Liouville theory solves a class of differential equations with conditions on this structure, a type of problem sometimes contrasted with initial value problems. The integral of a differential form in a region is equal to the integral of the derivative of that form on this structure for the region according to Stoke's theorem. For an N ball, it is an N minus one sphere, and points on this structure of a space are not in the space's interior. For 10 points, name this concept from mathematics which is roughly stated as the outer edge or the division between in the space and outside of it.
Lefschetz duality is used when a manifold has one of these structures.
boundary