Kuske, DLiu, JLohrey, M2011-11-272011-11-272010-07-112010-07-11Presentation at the 25th annual IEEE symposium on logic in computer science (LICS'10), Edinburgh, UK, pp. 160 - 169978-0-7695-4114-31043-6871https://hdl.handle.net/10292/2808Several new undecidability results on isomorphism problems for automatic structures are shown: (i) The isomorphism problem for automatic equivalence relations is \Pi^0_1-complete, (ii) The isomorphism problem for automatic trees of height n≥2 is \Pi^0_{2n-3}-complete, (iii) The isomorphism problem for automatic linear orders is not arithmetical.Paper and onlineCopyright © 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Arithmetical hierarchyAutomatic structuresIsomorphism problemsAutomataBoolean algebraConstruction industryHuman computer interactionPediatricsSiliconTerminologyConference ContributionOpenAccess10.1109/LICS.2010.10