The Isomorphism Problem on Classes of Automatic Structures

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Dietrich Kuske, Jiamou Liu, Markus Lohrey

Published: 2010, Last Modified: 21 Jan 2026LICS 2010EveryoneRevisionsBibTeXCC BY-SA 4.0
Abstract: Several new undecidability results on isomorphism problems for automatic structures are shown: (i) The isomorphism problem for automatic equivalence relations is Π10 -complete, (ii) The isomorphism problem for automatic trees of height n ≥ 2 is Π2n-30 -complete, (iii) The isomorphism problem for automatic linear orders is not arithmetical.