# Mathematics Colloquia and Seminars

For a mathematician, the word snowflake'' can have two different meanings. The first meaning conjures up mathematical objects with a recursive construction, often with fractal boundaries. The second kind are of course snow crystals of winter season. Growth of the latter is notoriously difficult to understand, as controlled experiments are impossible, basic physical principles poorly understood and most differential equation models difficult to analyze. We will first discuss a mathematical variety, a popular class of cellular automata known as Packard Snowflakes, for which a fairly complete mathematical theory exists. Then we will describe a much more realistic three-dimensional mesoscopic snow crystal growth model. The talk, on joint work with D. Griffeath (Univ. of Wisconsin), will feature many computer-generated pictures and movies, and will be accesible to most undergraduates.