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arXiv · 1609.02970

Definable Coherent Ultrapowers and Elementary Extensions

Will Boney
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Abstract

We develop the notion of coherent ultrafilters (extenders without normality or well-foundedness). We then use definable coherent ultraproducts to characterize any extension of a model $M$ in any fragment of $\mathbb{L}_{\infty, \omega}$ that defines Skolem functions by a sufficiently complete (but in $ZFC$) coherent ultrafilter. We apply this method to various elementary classes and AECs.

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Will Boney. 2016-09-09. Definable Coherent Ultrapowers and Elementary Extensions. https://arxiv.org/abs/1609.02970

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