English

The size of semigroup orbits modulo primes

Number Theory 2023-11-08 v1 Algebraic Geometry Dynamical Systems

Abstract

Let VV be a projective variety defined over a number field KK, let SS be a polarized set of endomorphisms of VV all defined over KK, and let PV(K)P\in V(K). For each prime p\mathfrak{p} of KK, let mp(S,P)m_{\mathfrak{p}}(S,P) denote the number of points in the orbit of PmodpP\bmod\mathfrak{p} for the semigroup of maps generated by SS. Under suitable hypotheses on SS and PP, we prove an analytic estimate for mp(S,P)m_{\mathfrak{p}}(S,P) and use it to show that the set of primes for which mp(S,P)m_{\mathfrak{p}}(S,P) grows subexponentially as a function of NK/Qp\operatorname{\mathsf{N}}_{K/\mathbb{Q}}\mathfrak{p} is a set of density zero. For V=P1V=\mathbb{P}^1 we show that this holds for a generic set of maps SS provided that at least two of the maps in SS have degree at least four.

Keywords

Cite

@article{arxiv.2303.14819,
  title  = {The size of semigroup orbits modulo primes},
  author = {Wade Hindes and Joseph H. Silverman},
  journal= {arXiv preprint arXiv:2303.14819},
  year   = {2023}
}

Comments

17 pages

R2 v1 2026-06-28T09:34:26.645Z