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21.
Diego Vaggione 《Studia Logica》1996,57(2-3):239-241
It is proved that the directly indecomposable algebras in a congruence modular equational class form a first-order class provided that fulfils some two natural assumptions.Research supported by CONICOR and SECYT (UNC).Presented by W. Dziobiak 相似文献
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This paper is the concluding part of [1] and [2], and it investigates the inner structure of the lattice (MHA) of all varieties of monadic Heyting algebras. For every n , we introduce and investigate varieties of depth n and cluster n, and present two partitions of (MHA), into varieties of depth n, and into varieties of cluster n. We pay a special attention to the lower part of (MHA) and investigate finite and critical varieties of monadic Heyting algebras in detail. In particular, we prove that there exist exactly thirteen critical varieties in (MHA) and that it is decidable whether a given variety of monadic Heyting algebras is finite or not. The representation of (MHA) is also given. All these provide us with a satisfactory insight into (MHA). Since (MHA) is dual to the lattice NExtMIPC of all normal extensions of the intuitionistic modal logic MIPC, we also obtain a clearer picture of the lattice structure of intuitionistic modal logics over MIPC. 相似文献
25.
This paper is devoted to the study of some subvarieties of the variety Qof Q-Heyting algebras, that is, Heyting algebras with a quantifier. In particular, a deeper investigation is carried out in the variety Q
3
of three-valued Q-Heyting algebras to show that the structure of the lattice of subvarieties of Qis far more complicated that the lattice of subvarieties of Heyting algebras. We determine the simple and subdirectly irreducible algebras in Q
3
and we construct the lattice of subvarieties (Q
3
) of the variety Q
3
. 相似文献
26.
Marcus Kracht 《Journal of Philosophical Logic》1998,27(1):49-73
In this paper we will study the properties of the least extension n() of a given intermediate logic by a strong negation. It is shown that the mapping from to n() is a homomorphism of complete lattices, preserving and reflecting finite model property, frame-completeness, interpolation and decidability. A general characterization of those constructive logics is given which are of the form n (). This summarizes results that can be found already in [13,14] and [4]. Furthermore, we determine the structure of the lattice of extensions of n(LC). 相似文献
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In [4], Caicedo and Cignoli study compatible functions on Heytingalgebras and the corresponding logical properties of connectivesdefined on intuitionistic propositional calculus. In this paperwe study some aspects of compatible functions on the algebrasassociated to positive propositional calculus and successiveextensions of it: intuitionistic calculus itself, the modalsymmetric propositional calculus of Moisil and n-valued ukasiewiczpropositional calculus. 相似文献
29.
Tarek Sayed Ahmed 《Studia Logica》2008,89(3):325-332
Following research initiated by Tarski, Craig and Németi, and futher pursued by Sain and others, we show that for certain
subsets G of
ω
ω, atomic countable G polyadic algebras are completely representable. G polyadic algebras are obtained by restricting the similarity type and axiomatization of ω-dimensional polyadic algebras to finite quantifiers and substitutions in G. This contrasts the cases of cylindric and relation algebras.
Presented by Robert Goldblatt 相似文献
30.
We consider various classes of algebras obtained by expanding idempotent semirings with meet, residuals and Kleene-*. An investigation of congruence properties (e-permutability, e-regularity, congruence distributivity) is followed by a section on algebraic Gentzen systems for proving inequalities in idempotent semirings, in residuated lattices, and in (residuated) Kleene lattices (with cut). Finally we define (one-sorted) residuated Kleene lattices with tests to complement two-sorted Kleene algebras with tests. 相似文献