English

The Skolem Problem in rings of positive characteristic

Logic in Computer Science 2026-03-12 v3 Number Theory

Abstract

We show that the Skolem Problem is decidable in finitely generated commutative rings of positive characteristic. More precisely, we show that there exists an algorithm which, given a finite presentation of a (unitary) commutative ring R=Z/T[X1,,Xn]/I\mathcal{R} = \mathbb{Z}_{/T}[X_1, \ldots, X_n]/I of characteristic T>0T > 0, and a linear recurrence sequence (γn)nNRN(\gamma_n)_{n \in \mathbb{N}} \in \mathcal{R}^{\mathbb{N}}, determines whether (γn)nN(\gamma_n)_{n \in \mathbb{N}} contains a zero term. Our proof is based on two recent results: Dong and Shafrir (2026) on the solution set of S-unit equations over pep^e-torsion modules, and Karimov, Luca, Nieuwveld, Ouaknine, and Worrell (2025) on solving linear equations over powers of two multiplicatively independent numbers. Our result implies, moreover, that the zero set of a linear recurrence sequence over a ring of characteristic T=p1e1pkekT = p_1^{e_1} \cdots p_k^{e_k} is effectively a finite union of pip_i-normal sets in the sense of Derksen (2007).

Keywords

Cite

@article{arxiv.2510.27603,
  title  = {The Skolem Problem in rings of positive characteristic},
  author = {Ruiwen Dong and Doron Shafrir},
  journal= {arXiv preprint arXiv:2510.27603},
  year   = {2026}
}

Comments

Corrected a small error in Lemma 3.2