English

Intersection of orbits for polynomials in characteristic $p$

Number Theory 2024-08-14 v1 Dynamical Systems

Abstract

In [GTZ08, GTZ12], the following result was established: given polynomials f,gC[x]f,g\in\mathbb{C}[x] of degrees larger than 11, if there exist α,βC\alpha,\beta\in\mathbb{C} such that their corresponding orbits Of(α)\mathcal{O}_f(\alpha) and Og(β)\mathcal{O}_g(\beta) (under the action of ff, respectively of gg) intersect in infinitely many points, then ff and gg must share a common iterate, i.e., fm=gnf^m=g^n for some m,nNm,n\in\mathbb{N}. If one replaces C\mathbb{C} with a field KK of characteristic pp, then the conclusion fails; we provide numerous examples showing the complexity of the problem over a field of positive characteristic. We advance a modified conjecture regarding polynomials ff and gg which admit two orbits with infinite intersection over a field of characteristic pp. Then we present various partial results, along with connections with another deep conjecture in the area, the dynamical Mordell-Lang conjecture.

Keywords

Cite

@article{arxiv.2408.06937,
  title  = {Intersection of orbits for polynomials in characteristic $p$},
  author = {Simone Coccia and Dragos Ghioca and Jungin Lee and Gyeonghyeon Nam},
  journal= {arXiv preprint arXiv:2408.06937},
  year   = {2024}
}

Comments

13 pages, comments welcome

R2 v1 2026-06-28T18:11:49.435Z