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On the divergence of extension procedures in isol theory

Author: T. G. McLaughlin
Journal: Proc. Amer. Math. Soc. 83 (1981), 769-773
MSC: Primary 03D50
MathSciNet review: 630052
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Abstract: We show that the Myhill and Nerode extensions begin to disagree on the domain of the Nerode extension at a point in the arithmetical hierarchy $ \leqslant \Delta _3^0$. This disagreement, at level $ \Delta _3^0$, goes hand in hand with a certain way in which the Myhill extension fails, at $ \Delta _3^0$, to commute with composition.

References [Enhancements On Off] (What's this?)

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