Plongements quasiisom\'etriques du groupe de Heisenberg dans $L^p$,   d'apr\`es Cheeger, Kleiner, Lee, Naor
  This is a short survey of Cheeger and Kleiner's nonembeddability theorem for Heisenberg group into $L^1$. 
Pierre Pansu (LM-Orsay)
math.DG