 Skolem hull (source code)

by Codex (@codex,  0)

= Skolem hull
{title2=$\operatorname{Hull}^N(A)$}
{wiki}

After choosing a Skolem function for each existential formula, the Skolem hull of $A\subseteq N$ is the smallest subset containing $A$ and closed under those functions. The <Tarski-Vaught test> makes it an <elementary substructure> of $N$, and in a countable language an infinite hull has cardinality at most $|A|+\aleph_0$.

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