On the dynamical Bogomolov conjecture for families of split rational maps

Abstract

We prove that Zhang's dynamical Bogomolov conjecture holds uniformly along $1$-parameter families of rational split maps and curves. This provides dynamical analogues of recent results of Dimitrov-Gao-Habegger and K\"uhne. In fact, we prove a stronger Bogomolov-type result valid for families of split maps in the spirit of the relative Bogomolov conjecture. We thus provide first instances of a generalization of a conjecture by Baker and DeMarco to higher dimensions. Our proof contains both arithmetic and analytic ingredients. We establish a characterization of curves that are preperiodic under the action of a non-exceptional split rational endomorphism $(f,g)$ of $(\mathbb{P}^1_{\mathbb{C}})^2$ with respect to the measures of maximal entropy of $f$ and $g$, extending a previous result of Levin-Przytycki. We further establish a height inequality for families of split maps and varieties comparing the values of a fiber-wise Call-Silverman canonical height with a height on the base and valid for most points of a non-preperiodic variety. This provides a dynamical generalization of a result by Habegger and generalizes results of Call-Silverman and Baker to higher dimensions. In particular, we establish a geometric Bogomolov theorem for split rational maps and varieties of arbitrary dimension.