Front formation in a ballistic annihilation model
  We study a simple one-dimensional model of ballisticaly-controlled annihilation in which the two annihilating species are initially spatially separated. The time dependent properties of the annihilation front are exactly derived. It is shown that the front wanders in a brownian fashion around its average value. 
Jaros{\l}aw Piasecki, Pierre-Antoine Rey and Michel Droz