On two theorems about local automorphisms of geometric structures
  This article investigates a few questions about orbits of local automorphisms in manifolds endowed with rigid geometric structures. We give sufficient conditions for local homogeneity in a broad class of such structures, namely Cartan geometries, extending a classical result of Singer about locally homogeneous Riemannian manifolds. We also revisit a strong result of Gromov which describes the structure of the orbits of local automorphisms of manifolds endowed with $A$-rigid structures, and give a statement of this result in the setting of Cartan geometries. 
Vincent Pecastaing
math.DG