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This article is cited in 1 scientific paper (total in 1 paper)
Isomorphisms, Definable Relations, and Scott Families for Integral Domains and Commutative Semigroups
D. A. Tusupov Sobolev Institute of Mathematics, Siberian Branch of the Russian Academy of Sciences
Abstract:
In the present article, we prove the following four assertions: (1) For every computable successor ordinal $\alpha$, there exists a $\Delta^0_\alpha$-categorical integral domain (commutative semigroup) which is not relatively $\Delta^0_\alpha$-categorical (i. e., no formally $\Sigma^0_\alpha$ Scott family exists for such a structure). (2) For every computable successor ordinal $\alpha$, there exists an intrinsically $\Sigma^0_\alpha$-relation on the universe of a computable integral domain (commutative semigroup) which is not a relatively intrinsically $\Sigma^0_\alpha$-relation. (3) For every computable successor ordinal $\alpha$ and finite $n$, there exists an integral domain (commutative semigroup) whose $\Delta^0_\alpha$-dimension is equal to $n$. (4) For every computable successor ordinal $\alpha$, there exists an integral domain (commutative semigroup) with presentations only in the degrees of sets $X$ such that $\Delta^0_\alpha(X)$ is not $\Delta^0_\alpha$. In particular, for every finite $n$, there exists an integral domain (commutative semigroup) with presentations only in the degrees that are not $n$-low.
Key words:
computable structure, Scott family, definable relation, integral domain, semigroup.
Received: 06.03.2006
Citation:
D. A. Tusupov, “Isomorphisms, Definable Relations, and Scott Families for Integral Domains and Commutative Semigroups”, Mat. Tr., 9:2 (2006), 172–190; Siberian Adv. Math., 17:1 (2007), 49–61
Linking options:
https://www.mathnet.ru/eng/mt52 https://www.mathnet.ru/eng/mt/v9/i2/p172
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