Dynatomic Galois groups for a family of quadratic rational maps

Abstract

For every nonconstant rational function [Formula: see text], the Galois groups of the dynatomic polynomials of [Formula: see text] encode various properties of [Formula: see text] are of interest in the subject of arithmetic dynamics. We study here the structure of these Galois groups as [Formula: see text] varies in a particular one-parameter family of maps, namely, the quadratic rational maps having a critical point of period 2. In particular, we provide explicit descriptions of the third and fourth dynatomic Galois groups for maps in this family.