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arXiv · 2010.00901

Two-variable logic has weak, but not strong, Beth definability

H. Andréka·I. Németi
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Abstract

We prove that the two-variable fragment of first-order logic has the weak Beth definability property. This makes the two-variable fragment a natural logic separating the weak and the strong Beth properties since it does not have the strong Beth definability property.

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H. Andréka, I. Németi. 2020-11-23. Two-variable logic has weak, but not strong, Beth definability. https://doi.org/10.1017/jsl.2021.7

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