A shape evolution model under affine transformations
  In this note we describe a discrete dynamical system acting on the similarity classes of a plane convex body within the affine class of the body. We find invariant elements in all affine classes, and describe the orbits of bodies in some special classes. We point out applications with abrasion processes of pebble shapes. 
G\'abor Domokos, Zsolt L\'angi and M\'ark Mezei
math.MG math.DS