Open Access
2006 Boolean Algebras, Tarski Invariants, and Index Sets
Barbara F. Csima, Antonio Montalbán, Richard A. Shore
Notre Dame J. Formal Logic 47(1): 1-23 (2006). DOI: 10.1305/ndjfl/1143468308


Tarski defined a way of assigning to each Boolean algebra, B, an invariant inv(B) ∈ In, where In is a set of triples from ℕ, such that two Boolean algebras have the same invariant if and only if they are elementarily equivalent. Moreover, given the invariant of a Boolean algebra, there is a computable procedure that decides its elementary theory. If we restrict our attention to dense Boolean algebras, these invariants determine the algebra up to isomorphism. In this paper we analyze the complexity of the question "Does B have invariant x?" For each x ∈ In we define a complexity class Γx that could be either Σⁿ, Πⁿ, Σⁿ ∧ Πⁿ, or Πω+1 depending on x, and we prove that the set of indices for computable Boolean algebras with invariant x is complete for the class Γx. Analogs of many of these results for computably enumerable Boolean algebras were proven in earlier works by Selivanov. In a more recent work, he showed that similar methods can be used to obtain the results for computable ones. Our methods are quite different and give new results as well. As the algebras we construct to witness hardness are all dense, we establish new similar results for the complexity of various isomorphism problems for dense Boolean algebras.


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Barbara F. Csima. Antonio Montalbán. Richard A. Shore. "Boolean Algebras, Tarski Invariants, and Index Sets." Notre Dame J. Formal Logic 47 (1) 1 - 23, 2006.


Published: 2006
First available in Project Euclid: 27 March 2006

zbMATH: 1107.03031
MathSciNet: MR2211179
Digital Object Identifier: 10.1305/ndjfl/1143468308

Primary: 03D50

Keywords: Boolean algebras , computability , index sets , Tarski invariants

Rights: Copyright © 2006 University of Notre Dame

Vol.47 • No. 1 • 2006
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