Surface Growth.

We begin with a simple model of growth which is called ballistic deposition. In this model (a one-dimensional version) one begins with a line on which growth will take place. Particles are now dropped vertically down from a randomly chosen point, high above, towards the line in question. Gravity plays no role in this process. The particle stops as soon as it finds a site which has a particle in the nearest neighbour position. At any instant the interface is the line joining the topmost particle of a given site. [ABSTRACT FROM AUTHOR]