Journal of Logic and Computation Advance Access originally published online on September 24, 2008
Journal of Logic and Computation 2009 19(1):177-197; doi:10.1093/logcom/exn023
This article appears in the following Journal of Logic and Computation issue: Special Issue: Logic and Computation in the Real World: CiE 2007 [View the issue table of contents]
Original Articles |
Undecidability in Some Structures Related to Computation Theory
A.P. Ershov Institute of Informatics Systems, Siberian Division Russian Academy of Sciences
E-mail: vseliv{at}nspu.ru
Received 10 October 2007.
We show that many of the so called discrete weak semilattices considered earlier in a series of author's publications have hereditary undecidable first-order theories. Since such structures appear naturally in some parts of computation theory, we obtain several new undecidability results. This applies e.g. to the structures of complete numberings, of m-degrees of index sets and of the Wadge degrees of k-partitions in the Baire space and
-algebraic domains. Whenever possible, we try to determine also the exact degrees of undecidability of the theories under discussion.
Keywords: Semilattice; discrete weak semilattice; partition; reducibility; undecidability; theory
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