English

Arithmetic progressions in polynomial orbits

Number Theory 2024-03-08 v1

Abstract

Let ff be a polynomial with integer coefficients whose degree is at least 2. We consider the problem of covering the orbit Orbf(t)={t,f(t),f(f(t)),}\operatorname{Orb}_f(t)=\{t,f(t),f(f(t)),\cdots\}, where tt is an integer, using arithmetic progressions each of which contains tt. Fixing an integer k2k\ge 2, we prove that it is impossible to cover Orbf(t)\operatorname{Orb}_f(t) using kk such arithmetic progressions unless Orbf(t)\operatorname{Orb}_f(t) is contained in one of these progressions. In fact, we show that the relative density of terms covered by kk such arithmetic progressions in Orbf(t)\operatorname{Orb}_f(t) is uniformly bounded from above by a bound that depends solely on kk. In addition, the latter relative density can be made as close as desired to 11 by an appropriate choice of kk arithmetic progressions containing tt if kk is allowed to be large enough.

Keywords

Cite

@article{arxiv.2403.04397,
  title  = {Arithmetic progressions in polynomial orbits},
  author = {Mohammad Sadek and Mohamed Wafik and Tuğba Yesin},
  journal= {arXiv preprint arXiv:2403.04397},
  year   = {2024}
}
R2 v1 2026-06-28T15:12:10.889Z