English

Preperiodic portraits for unicritical polynomials over a rational function field

Dynamical Systems 2021-08-12 v1 Number Theory

Abstract

Let KK be an algebraically closed field of characteristic zero, and let K:=K(t)\mathcal{K} := K(t) be the rational function field over KK. For each d2d \ge 2, we consider the unicritical polynomial fd(z):=zd+tK[z]f_d(z) := z^d + t \in \mathcal{K}[z], and we ask the following question: If we fix αK\alpha \in \mathcal{K} and integers M0M \ge 0, N1N \ge 1, and d2d \ge 2, does there exist a place pSpecK[t]\mathfrak{p} \in \operatorname{Spec} K[t] such that, modulo p\mathfrak{p}, the point α\alpha enters into an NN-cycle after precisely MM steps under iteration by fdf_d? We answer this question completely, concluding that the answer is generally affirmative and explicitly giving all counterexamples. This extends previous work by the author in the case that α\alpha is a constant point.

Keywords

Cite

@article{arxiv.1603.08138,
  title  = {Preperiodic portraits for unicritical polynomials over a rational function field},
  author = {John R. Doyle},
  journal= {arXiv preprint arXiv:1603.08138},
  year   = {2021}
}

Comments

18 pages + references

R2 v1 2026-06-22T13:19:09.843Z