Equations in free topoboolean algebra. (English. Russian original) Zbl 0624.03007

Algebra Logic 25, 109-127 (1986); translation from Algebra Logika 25, No. 2, 172-204 (1986).
Let \(\Lambda\) be a modal or superintuitionistic logic and \(F_{\omega}(\Lambda)\) the free algebra of rank \(\omega\) in the variety of algebras corresponding to \(\Lambda\). For each of the logics S4 and Int the author obtains the following main results. Let \(\Sigma_ f\) be the signature of \(F_{\omega}(\Lambda)\) enriched by the free generators as constant operations. Then: 1) The universal theory of \(F_{\omega}(\Lambda)\) is decidable and there exists an algorithm constructing an obstacle (i.e., roughly speaking, a counter-example) for those universal formulas of \(\Sigma_ f\) that are false in \(F_{\omega}(\Lambda)\). 2) There exists an algorithm verifying the solvability of equations in \(F_{\omega}(\Lambda)\) and finding the solutions of solvable equations.
Reviewer: S.Rudeanu


03B25 Decidability of theories and sets of sentences
03G10 Logical aspects of lattices and related structures
06B25 Free lattices, projective lattices, word problems
08B20 Free algebras
Full Text: DOI EuDML


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