In many metric spaces one can connect an arbitrary pair of points with a curve of finite length, but in Euclidean spaces one
can connect a pair of points with a lot of rectifiable curves, curves that are well distributed across a region. In the present
paper we give geometric criteria on a metric space under which we can find similar families of curves. We shall find these
curves by first solving a “dual” problem of building Lipschitz maps from our metric space into a sphere with good topological
properties. These families of curves can be used to control the values of a function in terms of its gradient (suitably interpreted
on a general metric space), and to derive Sobolev and Poincaré inequalities.
The author is supported by the U.S. National Science Foundation and grateful to IHES for its hospitality.