“…For instance, he proves that if noncompact initial data Γ 0 are allowed then one loses uniqueness of the generalized geometric evolution. In recent years, an interest has grown in the use of viscosity solutions of (first order) Hamilton-Jacobi equations defined on Riemannian manifolds (in relation to dynamical systems, to geometric problems, or from a theoretical point of view), see [32,11,12,4,31,10,23], but no second order theory, apart from Ilmanen's paper, has apparently been developed for parabolic equations (in the case of stationary, degenerate elliptic equations, such a study was recently started in [5]). …”