English

Dp-minimal expansions of $(\mathbb{Z},+)$ via dense pairs via Mordell-Lang

Logic 2020-04-16 v1

Abstract

This is a contribution to the classification problem for dp-minimal expansions of (Z,+)(\mathbb{Z},+). Let SS be a dense cyclic group order on (Z,+)(\mathbb{Z},+). We use results on "dense pairs" to construct uncountably many dp-minimal expansions of (Z,+,S)(\mathbb{Z},+,S). These constructions are applications of the Mordell-Lang conjecture and are the first examples of "non-modular" dp-minimal expansions of (Z,+)(\mathbb{Z},+). We canonically associate an o-minimal expansion R\mathcal{R} of (R,+,×)(\mathbb{R},+,\times), an R\mathcal{R}-definable circle group H\mathbb{H}, and a character ZH\mathbb{Z} \to \mathbb{H} to a "non-modular" dp-minimal expansion of (Z,+,S)(\mathbb{Z},+,S). We also construct a "non-modular" dp-minimal expansion of (Z,+,Valp)(\mathbb{Z},+,\mathrm{Val}_p) from the character ZZp×\mathbb{Z} \to \mathbb{Z}^\times_p, kexp(pk)k \mapsto \mathrm{exp}(pk).

Keywords

Cite

@article{arxiv.2004.06847,
  title  = {Dp-minimal expansions of $(\mathbb{Z},+)$ via dense pairs via Mordell-Lang},
  author = {Erik Walsberg},
  journal= {arXiv preprint arXiv:2004.06847},
  year   = {2020}
}

Comments

preliminary version, comments are welcome\