arXiv subjects

Eran Alouf

Publications and source records attributed to Eran Alouf.

4 recordsLinked to original sources

arXiv2024

Stable reducts of elementary extensions of Presburger arithmetic

Suppose $N$ is elementarily equivalent to an archimedean ordered abelian group $(G,+,<)$ with small quotients (for all $1 \leq n < \omega$, $[G: nG]$ is finite). Then every stable reduct of $N$ which expands $(G,+)$ (equivalently every reduct that does not add new unary definable sets) is interdefinable with $(G,+)$. This extends previous results on stable reducts of $(\mathbb{Z}, +, <)$ to (stable) reducts of elementary extensions of $\mathbb{Z}$. In particular this holds for $G = \mathbb{Z}$ and $G = \mathbb{Q}$. As a result we answer a question of Conant from 2018. This result is a corollary of a more general statement about expansions of weakly-minimal 1-based expansions of abelian groups with small quotients preserving the algebraic closure operator.

math.LO↗

arXiv2024

On dp-minimal expansions of the integers II

We first prove that if $\mathcal{Z}$ is a dp-minimal expansion of $\left(\mathbb{Z},+,0,1\right)$ which is not interdefinable with $\left(\mathbb{Z},+,0,1,<\right)$, then every infinite subset of $\mathbb{Z}$ definable in $\mathcal{Z}$ is generic in $\mathbb{Z}$. Using this, we prove that if $\mathcal{Z}$ is a dp-minimal expansion of $\left(\mathbb{Z},+,0,1\right)$ with monster model $G$ such that $G^{00}\neq G^{0}$, then for some $\alpha\in\mathbb{R}\backslash\mathbb{Q}$, the cyclic order on $\mathbb{Z}$ induced by the embedding $n\mapsto n\alpha+\mathbb{Z}$ of $\mathbb{Z}$ in $\mathbb{R}\big/\mathbb{Z}$ is definable in $\mathcal{Z}$. The proof employs the Gleason-Yamabe theorem for abelian groups.

math.LO↗

arXiv2020

On dp-minimal expansions of the integers

We show that if $ \mathcal{Z} $ is a dp-minimal expansion of $ \left(\mathbb{Z},+,0,1\right) $ that defines an infinite subset of $ \mathbb{N} $, then $ \mathcal{Z} $ is interdefinable with $ \left(\mathbb{Z},+,0,1, < \right) $. As a corollary, we show the same for dp-minimal expansions of $ \left(\mathbb{Z},+,0,1\right) $ which do not eliminate $ \exists^{\infty} $.

math.LO↗

arXiv2019

A new dp-minimal expansion of the integers

We consider the structure $(\mathbb{Z},+,0,|_{p_{1}},\dots,|_{p_{n}})$, where $x|_{p}y$ means $v_{p}(x)\leq v_{p}(y)$ and $v_p$ is the $p$-adic valuation. We prove that its theory has quantifier elimination in the language $\{+,-,0,1,(D_{m})_{m\geq1},|_{p_{1}},\dots,|_{p_{n}}\}$ where $D_m(x)\leftrightarrow \exists y ~ my = x$, and that it has dp-rank $n$. In addition, we prove that a first order structure with universe $\mathbb{Z}$ which is an expansion of $(\mathbb{Z},+,0)$ and a reduct of $(\mathbb{Z},+,0,|_{p})$ must be interdefinable with one of them. We also give an alternative proof for Conant's analogous result about $(\mathbb{Z},+,0,<)$.

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