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Computable categoricity and the Ershov hierarchy

✍ Scribed by Bakhadyr Khoussainov; Frank Stephan; Yue Yang


Publisher
Elsevier Science
Year
2008
Tongue
English
Weight
666 KB
Volume
156
Category
Article
ISSN
0168-0072

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## Abstract We investigate the computational complexity the class of Γ‐categorical computable structures. We show that hyperarithmetic categoricity is Ξ ^1^~1~‐complete, while computable categoricity is Ξ ^0^~4~‐hard. (Β© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)