Finitarity and definability of the closure operator

Let cl\operatorname{cl} be the invariant closure operator induced by the independence relation mathop{\mathpalette\Ind{}^{\!\!\!\!\rlap{\scriptscriptstyle\textnormal{}}\,\,\,\,}} on the monster structure C\mathfrak C.

Finitarity and definability conjecture. cl\operatorname{cl} is always finitary. Moreover, cl\operatorname{cl} is definable: for every small ACA\subseteq\mathfrak C, the set cl(A)\operatorname{cl}(A) is ord-definable over AA.

The preceding proposition establishes finitarity when the independence relation is superior, but the general finitarity and definability assertions are left as conjectural properties of the closure operator.

Sources & referencesView supporting material

Primary source

Antongiulio Fornasiero, “Lovely pairs for independence relations”, arXiv:1009.5244 (2010).

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