# Dynamical Uniform Bounds for Fibers and a Gap Conjecture

## TL;DR

This paper proves a uniform version of the Dynamical Mordell-Lang Conjecture for étale maps and establishes a gap result for the growth rate of heights in orbits of endomorphisms on quasiprojective varieties over number fields.

## Contribution

It introduces a uniform bound on the number of orbit points mapping to a fixed point and a gap result for height growth rates in dynamical systems on algebraic varieties.

## Key findings

- Finite preimages under étale endomorphisms are uniformly bounded.
- Height growth in orbits is either finite or grows faster than logarithmic rate.
- Provides a new gap theorem for height growth in algebraic dynamics.

## Abstract

We prove a uniform version of the Dynamical Mordell-Lang Conjecture for \'etale maps; also, we obtain a gap result for the growth rate of heights of points in an orbit along an arbitrary endomorphism of a quasiprojective variety defined over a number field. More precisely, for our first result, we assume $X$ is a quasi-projective variety defined over a field $K$ of characteristic $0$, endowed with the action of an \'etale endomorphism $\Phi$, and $f\colon X\to Y$ is a morphism with $Y$ a quasi-projective variety defined over $K$. Then for any $x\in X(K)$, if for each $y\in Y(K)$, the set $S_y:=\{n\in \mathbb{N}\colon f(\Phi^n(x))=y\}$ is finite, then there exists a positive integer $N$ such that $\#S_y\le N$ for each $y\in Y(K)$. For our second result, we let $K$ be a number field, $f:X\dashrightarrow \mathbb{P}^1$ is a rational map, and $\Phi$ is an arbitrary endomorphism of $X$. If $\mathcal{O}_\Phi(x)$ denotes the forward orbit of $x$ under the action of $\Phi$, then either $f(\mathcal{O}_\Phi(x))$ is finite, or $\limsup_{n\to\infty} h(f(\Phi^n(x)))/\log(n)>0$, where $h(\cdot)$ represents the usual logarithmic Weil height for algebraic points.