Sub-Riemannian Geometry and Geodesics in Banach Manifolds
  In this paper, we define and study sub-Riemannian structures on Banach manifolds. We obtain extensions of the Chow-Rashevski theorem for exact controllability, and give conditions for the existence of a Hamiltonian geodesic flow despite the lack of a Pontryagin Maximum Principle in the infinite dimensional setting. 
Sylvain Arguillere
math.DG