  Let phi(z) be a polynomial of degree at least 2 with coefficients in a number
field K. Iterating phi gives rise to a dynamical system and a corresponding
canonical height function, as defined by Call and Silverman. We prove a simple
product formula relating the transfinite diameters of the filled Julia sets of
phi over various completions of K, and we apply this formula to give a
generalization of Bilu's equidistribution theorem for sequences of points whose
canonical heights tend to zero.
