A sub-Riemannian distance is obtained when minimizing lengths of paths which are tangent to a distribution of planes. Such distances differ substantially from Riemannian distances, even in the simplest example, the 3-dimensional Heisenberg group. This raises many questions in metric geometry: embeddability in Banach spaces, bi-Lipschitz or bi-Hölder comparison of various examples. Emphasis will be put on Gromov's results on the Hölder homeomorphism problem, and on a quasisymmetric version of it motivated by Riemannian geometry.[-]

On conformally compact manifolds of arbitrary signature I will describe a natural boundary calculus for computing the asymptotics of a class of natural boundary problems. This is applied to the non-linear problem of finding, conformally, a conformally compact constant scalar curvature metric on the interior of a manifold with boundary. This problem was studied from a different point of view by Andersson, Chrusciel, Friedrich (ACF) in 1992. They identified a conformal submanifold invariant that obstructs smooth boundary asymptotics for the problem on 3-manifolds (and gave some information on the obstructions in other dimensions). This invariant is the same as that arising from the variation of the Willmore energy. We find higher order submanifold invariants that generalise that curvature quantity found by ACF. This construction also leads to a route for manufacturing large classes of other conformal submanifold invariants.[-]