A Useful Undecidable Theory
نویسنده
چکیده
We show that many so called discrete weak semilattices considered earlier in a series of author’s publications have hereditary undecidable first-order theories. Since such structures appear naturally in some parts of computability theory, we obtain several new undecidability results. This applies e.g. to the structures of complete numberings, of m-degrees of index sets and of the Wadge degrees of partitions in the Baire space and ω-algebraic domains.
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