Star sorts, Lelek fans, and the reconstruction of non-$\aleph_0$-categorical theories in continuous logic - Archive ouverte HAL
Pré-Publication, Document De Travail Année : 2022

Star sorts, Lelek fans, and the reconstruction of non-$\aleph_0$-categorical theories in continuous logic

Résumé

We prove a reconstruction theorem valid for arbitrary theories in continuous (or classical) logic in a countable language, that is to say that we provide a complete bi-interpretation invariant for such theories, taking the form of an open Polish topological groupoid. More explicitly, for every such theory $T$ we construct a groupoid $\mathbf{G}^*(T)$ that only depends on the bi-interpretation class of $T$, and conversely, we reconstruct from $\mathbf{G}^*(T)$ a theory that is bi-interpretable with $T$. The basis of $\mathbf{G}^*(T)$ (namely, the set of objects, when viewed as a category) is always homeomorphic to the Lelek fan. We break the construction of the invariant into two steps. In the second step we construct a groupoid from any \emph{reconstruction sort}, while in the first step such a sort is constructed. This allows us to place our result in a common framework with previously established ones, which only differ by their different choice of a reconstruction sort.
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Dates et versions

hal-03596567 , version 1 (03-03-2022)
hal-03596567 , version 2 (25-03-2022)
hal-03596567 , version 3 (06-07-2022)

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Itaï Ben Yaacov. Star sorts, Lelek fans, and the reconstruction of non-$\aleph_0$-categorical theories in continuous logic. 2022. ⟨hal-03596567v1⟩
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