New families satisfying the Dynamical Uniform Boundedness Principle over function fields

Abstract

We extend a technique, originally due to the first author and Poonen, for proving cases of the Strong Uniform Boundedness Principle (SUBP) in algebraic dynamics over function fields of positive characteristic. The original method applied to unicritical polynomials for which the characteristic does not divide the degree. We show that many new 1-parameter families of polynomials satisfy the SUBP, including the family of all quadratic polynomials in even characteristic. We also give a new family of non-polynomial, non-Lattès rational functions that satisfies the SUBP.

14 pages; main results now hold over 1-dimensional function fields over arbitrary fields of positive characteristic (not just finite fields); to appear in Mathematische Annalen