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A SPARSITY RESULT FOR THE DYNAMICAL MORDELL–LANG CONJECTURE IN POSITIVE CHARACTERISTIC

Published online by Cambridge University Press:  23 February 2021

DRAGOS GHIOCA*
Affiliation:
Department of Mathematics, University of British Columbia, Vancouver, BCV6T 1Z2, Canada
ALINA OSTAFE
Affiliation:
School of Mathematics and Statistics, University of New South Wales, Sydney, NSW2052, Australia e-mail: [email protected]
SINA SALEH
Affiliation:
Department of Mathematics, University of British Columbia, Vancouver, BCV6T 1Z2, Canada e-mail: [email protected]
IGOR E. SHPARLINSKI
Affiliation:
School of Mathematics and Statistics, University of New South Wales, Sydney, NSW2052, Australia e-mail: [email protected]

Abstract

We prove a quantitative partial result in support of the dynamical Mordell–Lang conjecture (also known as the DML conjecture) in positive characteristic. More precisely, we show the following: given a field K of characteristic p, a semiabelian variety X defined over a finite subfield of K and endowed with a regular self-map $\Phi :X{\longrightarrow } X$ defined over K, a point $\alpha \in X(K)$ and a subvariety $V\subseteq X$ , then the set of all nonnegative integers n such that $\Phi ^n(\alpha )\in V(K)$ is a union of finitely many arithmetic progressions along with a subset S with the property that there exists a positive real number A (depending only on X, $\Phi $ , $\alpha $ and V) such that for each positive integer M,

$$\begin{align*}\scriptsize\#\{n\in S\colon n\le M\}\le A\cdot (1+\log M)^{\dim V}.\end{align*}$$

Type
Research Article
Copyright
© 2021 Australian Mathematical Publishing Association Inc.

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Footnotes

D. Ghioca and S. Saleh were partially supported by a Discovery Grant from NSERC, A. Ostafe by ARC Grants DP180100201 and DP200100355, and I. Shparlinski by ARC Grant DP200100355.

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