The Prime Spectrum of an MV-Algebra

In this paper we show that the prime ideal space of an MV-algebra is the disjoint union of prime ideal spaces of suitable local MV-algebras. Some special classes of algebras are defined and their spaces are investigated. The space of minimal prime ideals is studied as well. Mathematics Subject Classification : 03B50, 06D99.     

Yosida Type Representation for Perfect MV-Algebras

In [9] Mundici introduced a categorical equivalence Γ between the category of MV-algebras and the category of abelian ??-groups with strong unit. Using Mundici's functor Γ, in [8] the authors established an equivalence between the category of perfect MV-algebras and the category of abelian ??-groups. Aim of the present paper is to use the above functors to provide Yosida like representations (see [4]) of a large class of MV-algebras. Mathematics Subject Classification: 03G20, 03B50, 06D30, 06F20.     

Quasi-Stone algebras

The purpose of this paper is to define and investigate the new class of quasi-Stone algebras (QSA's). Among other things we characterize the class of simple QSA's and the class of subdirectly irreducible QSA's. It follows from this characterization that the subdirectly irreducible QSA's form an elementary class and that the variety of QSA's is locally finite. Furthermore we prove that the lattice of subvarieties of QSA's is an (ω + 1)-chain. MSC: 03G25, 06D16, 06E15.     

Good and Bad Infinitesimals,and States on Pseudo MV-algebras

We study relations among the set of infinitesimal elements of pseudo MV-algebras and the problem of existence of states on them. This is important because in contrast to MV-algebras, it can happen that a pseudo MV-algebra has no states, so no probabilistic evaluation of events on it is possible. We introduce two kinds of radicals, and we deal with their relation. In some cases, they are completely different, which is not the case for MV-algebras. We give many interesting examples describing different situations, and we deal in more details with a subvariety of symmetric pseudo MV-algebras, where both complements coincide. Mathematics Subject Classifications (2000) 06D35, 03B50, 03G12.     

Commutator-Finite D-Lattices

Commutator-finite D-lattices as a generalization of commutator-finite orthomodular lattices are defined and their properties studied. A necessary and sufficient condition is found under which a D-lattice can be uniquely decomposed into a direct product of an MV-algebra and finitely many irreducible D-lattices which are not MV-algebras. This condition is satisfied if the D-lattice is orthocomplete or if all commutators are sharp. A condition under which a block-finite D-lattice is commutator-finite is found. Some necessary and sufficient conditions for the existence of states and valuations are proved, and some examples are given. Mathematics Subject Classifications (2000) Primary 06F05; Secondary 03G25, 81P10.This research is supported by grant VEGA 2/3163/23.     

On the structure of rotation-invariant semigroups

 We generalize the notions of Girard algebras and MV-algebras by introducing rotation-invariant semigroups. Based on a geometrical characterization, we present five construction methods which result in rotation-invariant semigroups and in particular, Girard algebras and MV-algebras. We characterize divisibility of MV-algebras, and point out that integrality of Girard algebras follows from their other axioms. Received: 7 January 2002 / Revised version: 4 April 2002 / Published online: 19 December 2002 RID="*" ID="*" Supported by the National Scientific Research Fund Hungary (OTKA F/032782). Mathematics Subject Classification (2000): 20M14, 06F05 Key words or phrases: Residuated lattice – Conjunction for non-classical logics     

Compact representations of BL-algebras

In this paper we define sheaf spaces of BL-algebras (or BL-sheaf spaces), we study completely regular and compact BL-sheaf spaces and compact representations of BL-algebras and, finally, we prove that the category of non-trivial BL-algebras is equivalent with the category of compact local BL-sheaf spaces. Mathematics Subject Classification (2000):08A72, 03G25, 54B40, 06F99, 06D05     

The Lattice of Deductive Systems on Hilbert Algebras

The concept of deductive system on a Hilbert algebra was introduced by A. Diego. We show that the set Ded A of all deductive systems on a Hilbert algebra A forms an algebraic lattice which is distributive.AMS Classification (2000): 06F35, 03G25, 08A30     

Representation Theorems for Quantales

In this paper we prove that any quantale Q is (isomorphic to) a quantale of suitable relations on Q. As a consequence two isomorphism theorems are also shown with suitable sets of functions of Q into Q. These theorems are the mathematical background one needs in order to give natural and complete semantics for (non-commutative) Linear Logic using relations. Mathematics Subject Classification: 06D05, 06D10, 06D20, 03G25.     

Hájek basic fuzzy logic and Łukasiewicz infinite-valued logic

 Using the theory of BL-algebras, it is shown that a propositional formula ϕ is derivable in Łukasiewicz infinite valued Logic if and only if its double negation ˜˜ϕ is derivable in Hájek Basic Fuzzy logic. If SBL is the extension of Basic Logic by the axiom (φ & (φ→˜φ)) → ψ, then ϕ is derivable in in classical logic if and only if ˜˜ ϕ is derivable in SBL. Axiomatic extensions of Basic Logic are in correspondence with subvarieties of the variety of BL-algebras. It is shown that the MV-algebra of regular elements of a free algebra in a subvariety of BL-algebras is free in the corresponding subvariety of MV-algebras, with the same number of free generators. Similar results are obtained for the generalized BL-algebras of dense elements of free BL-algebras. Received: 20 June 2001 / Published online: 2 September 2002 This paper was prepared while the first author was visiting the Universidad de Barcelona supported by INTERCAMPUS Program E.AL 2000. The second author was partially supported by Grants 2000SGR-0007 of D. G. R. of Generalitat de Catalunya and PB 97-0888 of D. G. I. C. Y. T. of Spain. Mathematics Subject classification (2000): 03B50, 03B52, 03G25, 06D35 Keywords or Phrases: Basic fuzzy logic – Łukasiewicz logic – BL-algebras – MV-algebras – Glivenko's theorem     

Information Algebras and Consequence Operators

We explore a connection between different ways of representing information in computer science. We show that relational databases, modules, algebraic specifications and constraint systems all satisfy the same ten axioms. A commutative semigroup together with a lattice satisfying these axioms is then called an “information algebra”. We show that any compact consequence operator satisfying the interpolation and the deduction property induces an information algebra. Conversely, each finitary information algebra can be obtained from a consequence operator in this way. Finally we show that arbitrary (not necessarily finitary) information algebras can be represented as some kind of abstract relational database called a tuple system. Mathematics Subject Classification (2000): Primary 03B22; Secondary 03G15 03G25 08A70 68Q99 94A99 03C950     

On the Adjoint Monoids of Implicative BCK-algebras

We give some semigroup characterizations for implicative BCK-algebras, and prove that the adjoint semigroups of implicative BCK-algebras are residualed semigroups.AMS Subject Classification (2000): 03G25, 06F35     

States on commutative basic algebras

The paper deals with states on commutative basic algebras that are a non-associative generalization of MV-algebras or, in other words, the algebraic semantics for a fuzzy logic which generalizes the ?ukasiewicz logic in that the conjunction is not associative. States are defined in the same way as Mundici's states on MV-algebras as normalized finitely additive [0,1]-valued functions, and some results analogous to the results that are known from MV-algebras are proved.     

Complete Commutative Basic Algebras

By a basic algebra is meant an MV-like algebra (A, ⊕, ¬, 0) of type 〈2, 1, 0〉 derived in a natural way from bounded lattices having antitone involutions on their principal filters. In the previous paper (Botur and Hala?, Mult. Valued Log. Soft Comp., 2007) we have shown that finite basic algebras for which the operation ⊕ is commutative are MV-algebras. In this paper we generalize this result by considering commutative basic algebras for which the underlying lattice is complete.     

On the predecessor relation in abstract algebras

In this paper we generalize the Dedekind theory of order for the natural numbers N to abstract algebras with arbitrarily many finitary or infinitary operations. For any algebra ??, we introduce an algebraic predecessor relation P?? and its transitive hull P*?? coinciding in N with the unary injective successor function' resp. the >-relation. For some important classes of algebras ??, including Peano algebras (absolutely free algebras, word algebras), the algebraic predecessor relation is well-founded. Hence, its transitive hull, the natural ordering >?? of ??, is a well-founded partial order, which turns out to be a convenient device for classifying Peano algebras with respect to the number of operations and their arities. Moreover, the property of well-foundedness is an efficient tool for giving simple proofs of structure theorems as, e. g., that the class of all Peano algebras is closed under subalgebras and non-void direct products. - Finally, we will show how in the case of a formal language ??, i. e., the Peano algebra ?? of expressions (= terms & formulas), relations P??, resp. P*_?? can be used to define basic syntactical notions as occurences of free and bound variables etc. without any reference to a particular representation (“coding”) of the formal language. MSC: 03B22, 03E30, 03E75, 03F35, 08A55, 08B20.     

On poset Boolean algebras of scattered posets with finite width

We prove that the poset algebra of every scattered poset with finite width is embeddable in the poset algebra of a well ordered poset.Mathematics Subject Classification (2000):Primary 03G05, 06A06, 06A11; Secondary 08A05, 54G12     

Topological centers of certain dual algebras

Let be a Banach algebra with a bounded approximate identity. Let and be, respectively, the topological centers of the algebras and . In this paper, for weakly sequentially complete Banach algebras, in particular for the group and Fourier algebras and , we study the sets , , the relations between them and with several other subspaces of or .

     

L-algebras and three main non-classical logics

The semantics of three main branches of non-classical logic, intuitionistic, many-valued, and quantum logic, is unified by the concept of L-algebra. The corresponding three classes of algebras (Heyting algebras, MV-algebras, and orthomodular lattices) are associated to specializations of a bounded L-algebra, given by simple equations. Three basic specializations lead to three more classes of algebras, including quantized Heyting algebras which have not been considered before. All these algebras are obtained from a new class of L-algebras which simultaneously satisfy general versions of Glivenko's and Mundici's theorems.     

There exist subdirectly irreducible commutative basic algebras of an arbitrary infinite cardinality which are not MV-algebras

It was recently proved by P. Wojciechowski that for any infinite cardinal there exists a linearly ordered MV-algebra of this cardinality. Since basic algebras are a (non-associative) generalization of MV-algebras, there rises a natural question if this is true also for basic algebras which are not MV-algebras. Using the construction by P. Wojciechowski and the modified construction by the first author, we can set up certain defectors which enable us to prove the result of the title.     

Fuzzy Order Filters in Adjoint Semigroups of BCK-Algebras

In this paper, we introduce the notion of fuzzy order filters in adjoint semigroups of BCK-algebras. We prove that there is a bijection between the fuzzy ideals of BCK-algebras X and the fuzzy order filters in the adjoint semigroup M(X) of X.AMS Subject Classification (2000) 06F35 03G25 20M10