Diffusion for the periodic wind-tree model
  The periodic wind-tree model is an infinite billiard in the plane with identical rectangular scatterers disposed at each integer point. We prove that independently of the size of the scatterers, generically with respect to the angle, the polynomial diffusion rate in this billiard is 2/3. 
Vincent Delecroix, Pascal Hubert and Samuel Leli\`evre
math.DS math-ph math.MP