Stable groups and expansions of $(\mathbb{Z},+,0)$

Abstract

We show that if $G$ is a sufficiently saturated stable group of finite weight with no infinite, infinite-index, chains of definable subgroups, then $G$ is superstable of finite $U$-rank. Combined with recent work of Palacin and Sklinos, we conclude that $(\mathbb{Z},+,0)$ has no proper stable expansions of finite weight. A corollary of this result is that if $P\subseteq {\mathbb{Z}}^n$ is definable in a finite dp-rank expansion of $(\mathbb{Z},+,0)$, and $(\mathbb{Z},+,0,P)$ is stable, then $P$ is definable in $(\mathbb{Z},+,0)$. In particular, this answers a question of Marker on stable expansions of the group of integers by sets definable in Presburger arithmetic.

arXiv comment10 pages, final version to appear in Fundamenta Mathematicae