Diffusing Populations: Ghosts or Folks?

Abstract

Random walk phenomena abound in engineering contexts, from pedestrian traffic to cell motility in tissue engineering. We contrast two random walk models. The ghost model involves individuals who pass through each other unhindered. The folks model involves agents that interact by refusing to share the same location. Simple simulations reveal behaviour consistent with classical diffusion ideas. Using intuitive arguments, we demonstrate how the models are naturally associated with partial differential equations. Seductive opportunities for the misinterpretation of experimental data are discussed.