Effective categoricity of equivalence Structures
| Autor: | Calvert, W., Cenzer, D., Harizanov, V. S., Morozov, A. |
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| Rok vydání: | 2008 |
| Předmět: | |
| Zdroj: | Annals of Pure and Applied Logic 141 (2006) 61--78 |
| Druh dokumentu: | Working Paper |
| Popis: | An equivalence structure is a set with a single binary relation, satisfying sentences stating that the relation is an equivalence relation. A computable structure A is said to be $\Delta^0_\alpha$ categorical if for any computable structure B isomorphic to A there is a $\Delta^0_\alpha$ function witnessing that the two are isomorphic. The present paper gives an exact characterization of $\Delta^0_\alpha$ equivalence structures where $\alpha = 1$ or $\alpha \geq 3$. Extensive results for $\alpha = 2$ are also given, and open cases are exhaustively described. Comment: Improved form published |
| Databáze: | arXiv |
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