Goldbug Variations

This "Mathematical Entertainments" column from the Intelligencer is an exposition of current investigations, rooted in recent work of Jim Propp, into "quasirandom" analogues of random walk and random aggregation processes. Featured are the "Goldbugs" and the "Rotor-router". These are deterministic processes which simulate the random ones, for example having the same limiting states, but with faster convergence. The paper includes three large illustrations, which appear twice in the submission, as both raster image (.png) and postscript (.eps) files. The latter are much larger but needed for latex inclusion; the former are smaller, used by pdflatex, and better for pixel-level viewing.