Pseudo-t-norms and pseudo-BL algebras

BL algebras were introduced by Hájek as algebraic structures for his Basic Logic, starting from continuous t-norms on [0,1]. MV algebras, product algebras and Gödel algebras are particular cases of BL algebras. On the other hand, the pseudo-MV algebras extend the MV-algebras in the same way in which the arbitrary l-groups extend the abelian l-groups. We have generalized the BL algebras and pseudo-MV algebras, introducing the pseudo-BL algebras. In this paper we introduce weak-BL algebras and weak-pseudo-BL algebras. We also introduce non-commutative t-norms (we call them pseudo-t-norms) and use them in constructing pseudo-BL algebras and weak-pseudo-BL algebras.     

Sub-effect algebras and Boolean sub-effect algebras

 We show that Boolean effect algebras may have proper sub-effect algebras and conversely. Properties of lattice effect algebras with two blocks are shown. One condition of the completness of effect algebras is given. We also show that a lattice effect algebra associated to an orthomodular lattice can be embedded into a complete effect algebra iff the orthomodular lattice can be embedded into a complete orthomodular lattice.     

Pseudo-BCK algebras as partial algebras

It is well-known that the representation of several classes of residuated lattices involves lattice-ordered groups. An often applicable method to determine the representing group (or groups) from a residuated lattice is based on partial algebras: the monoidal operation is restricted to those pairs that fulfil a certain extremality condition, and else left undefined. The subsequent construction applied to the partial algebra is easy, transparent, and leads directly to the structure needed for representation.In this paper, we consider subreducts of residuated lattices, the monoidal and the meet operation being dropped: the resulting algebras are pseudo-BCK semilattices. Assuming divisibility, we can pass on to partial algebras also in this case. To reconstruct the underlying group structure from this partial algebra, if applicable, is again straightforward. We demonstrate the elegance of this method for two classes of pseudo-BCK semilattices: semilinear divisible pseudo-BCK algebras and cone algebras.     

On pseudo-BL algebras and BCC-algebras

We further study the filter theory of pseudo-BL algebras. We give some equivalent conditions of filter, normal filter and Boolean filter. We introduce the notion of pseudo MV-filter, pseudo-G filter and characterize Boolean algebras, pseudo-MV algebras and pseudo Gödel algebras (i.e. Gödel algebras) in pseudo-BL algebras. We establish the connections between BCC-algebras, pseudo-BCK algebras, pseudo-BL algebras and weak pseudo-BL algebras (pseudo-MTL algebras).     

An encoding of partial algebras as total algebras

We introduce a semantic encoding of partial algebras as total algebras through a Horn axiomatization of the existence equality relation interpreted as an algebraic operation. We show that this novel encoding enjoys several important properties that make it a good tool for the execution of partial algebraic specifications through means specific to ordinary algebraic reasoning, such as term rewriting.     

On BCK algebras: Part II: New algebras. The ordinal sum (product) of two bounded BCK algebras

Since all the algebras connected to logic have, more or less explicitly, an associated order relation, it follows, by duality principle, that they have two presentations, dual to each other. We classify these dual presentations in “left” and “right” ones and we consider that, when dealing with several algebras in the same research, it is useful to present them unitarily, either as “left” algebras or as “right” algebras. In some circumstances, this choice is essential, for instance if we want to build the ordinal sum (product) between a BL algebra and an MV algebra. We have chosen the “left” presentation and several algebras of logic have been redefined as particular cases of BCK algebras. We introduce several new properties of algebras of logic, besides those usually existing in the literature, which generate a more refined classification, depending on the properties satisfied. In this work (Parts I–V) we make an exhaustive study of these algebras—with two bounds and with one bound—and we present classes of finite examples, in bounded case. In Part II, we continue to present new properties, and consequently new algebras; among them, bounded α γ algebra is a common generalization of MTL algebra and divisible bounded residuated lattice (bounded commutative Rl-monoid). We introduce and study the ordinal sum (product) of two bounded BCK algebras. Dedicated to Grigore C. Moisil (1906–1973).     

Embeddings of generalized effect algebras into complete effect algebras

Generalized effect algebras as posets are unbounded versions of effect algebras having bounded effect-algebraic extensions. We show that when the MacNeille completion MC(P) of a generalized effect algebra P cannot be organized into a complete effect algebra by extending the operation ⊕ onto MC(P) then still P may be densely embedded into a complete effect algebra. Namely, we show these facts for Archimedean GMV-effect algebras and block-finite prelattice generalized effect algebras. Moreover, we show that extendable commutative BCK-algebras directed upwards are equivalent to generalized MV-effect algebras.     

Complexity of Boolean algebras

We show that the elementary theory of Boolean algebras is _log-complete for the Berman complexity class _c<ω STA(*, 2^cn, n), the class of sets accepted by alternating Turing machines running in time 2^cn for some constant c and making at most n alternations on inputs of length n; thus the theory is computationally equivalent to the theory of real addition with order. We extend the completeness results to various subclasses of Boolean algebras, including the finite, free, atomic, atomless, and complete Boolean algebras. Finally we show that the theory of any finite collection of finite Boolean algebras is complete for PSPACE, while the theory of any other collection is _log-hard for _c<ω STA(*, 2^cn, n).     

Pseudo equality algebras: revision

Recently Jenei introduced a new structure called equality algebras which is inspired by ideas of BCK-algebras with meet. These algebras were generalized by Jenei and Kóródi to pseudo equality algebras which are aimed to find a connection with pseudo BCK-algebras with meet. We show that such pseudo equality algebras are an equality algebras. Therefore, we define a new type of algebras, called JK-algebras, which more precisely reflects the relation to pseudo BCK-algebras with meet in the sense of Kabziński and Wroński. We describe congruences via normal closed deductive systems, and we show that the variety of JK-algebras is subtractive, congruence distributive and congruence permutable.     

Ideals and congruences of basic algebras

MV-algebras as well as orthomodular lattices can be seen as a particular case of so-called “basic algebras” which are an alter ego of bounded lattices whose sections are equipped with fixed antitone involutions. The class of basic algebras is an ideal variety. In the paper, we give an internal characterization of congruence kernels (ideals) and find a finite basis of ideal terms, with focus on monotone and effect basic algebras. We also axiomatize basic algebras that are subdirect products of linearly ordered ones.     

Gröbner bases in universal enveloping algebras of Leibniz algebras

We give a proof of the Poincaré–Birkhoff–Witt theorem for universal enveloping algebras of finite dimensional Leibniz algebras using Gröbner bases in a free associative algebra.     

Torsion elements in effect algebras

We define the torsion element in effect algebras and use it to characterize MV-effect algebra and 0-homogeneous effect algebras in chain-complete effect algebras. As an application, we prove that every element of an orthocomplete homogeneous atomic effect algebra has a unique basic decomposition into a sum of a sharp element and unsharp multiples of atoms. Further, we characterize homogeneity by the set of all sharp elements in orthocomplete atomic effect algebras.     

Complete classification of finite-dimensional estimation algebras of maximal rank

The idea of using estimation algebras to construct finite-dimensional non-linear filters was first proposed by Brockett and Clark, and Mitter independently. In his famous talk at the International Congress of Mathematics in 1983, Brockett proposed to classify all finite-dimensional estimation algebras. In this paper we explain why the theory of estimation algebras plays an important role in non-linear filtering. We show how to use the Wei-Norman approach to construct finite-dimensional filters from finite-dimensional estimation algebras. We survey some results in estimation algebras after 1984. We give a self-contained proof of complete classification of finite-dimensional estimation algebras of maximal rank in one place. The proof given here is simpler than those proofs scattered in several papers. This provides the readers with a complete coherent view of the important topic of the classification of finite-dimensional estimation algebras.     

Classification of four-dimensional estimation algebras

Of central importance in nonlinear filtering theory is the classification of finite-dimensional estimation algebras, through which we can construct recursive filters. We classify all t-dimensional estimation algebras, t⩽4, for arbitrary state space dimension     

Process algebras for systems diagnosis

In this paper we propose a new characterization of model-based diagnosis based on process algebras, a framework which is widely used in several areas of computer science. We show that process algebras provide a powerful modelling language which allows us to capture, in an uniform way, different types of models of physical systems, including models of time-varying and dynamic behavior. Then we provide a characterization of diagnosis which is equivalent to the “classical” abductive one. This suggests new interesting opportunities for research on relations between model-based reasoning and process algebras.     

On effect algebras of fuzzy sets

We introduce the category IE of effect algebras of fuzzy sets and sequentially continuous effect homomorphisms and describe its fundamental properties. We show that IE and the category ID of D-posets of fuzzy sets are isomorphic, hence the constructions and properties of ID related to applications to probability theory are valid for the corresponding effect algebras. We describe basic properties of categorical coproducts in ID and dually of categorical products in the corresponding category MID of measurable spaces. We end with remarks on fuzzy probability notions. Supported by VEGA Grant 1/2002/05.     

0-homogeneous effect algebras

In the present paper, we introduce a proper superclass of homogeneous effect algebras. We call this superclass as 0-homogeneous effect algebras. We prove that in every 0-homogeneous effect algebra, the set of all sharp elements forms a subalgebra. Every chain-complete 0-homogeneous effect algebra is homogeneous.     

Very true operators in effect algebras

We introduce the concept of very true operator on an effect algebra. Although an effect algebra is only partial, we define it in the way which is in accordance with traditional definitions in residuated lattices or basic algebras. This is possible if we require monotonicity as an additional condition. We prove that very true operators on effect algebras can be characterized by means of certain subsets which are conditionally complete.     

Intervals in generalized effect algebras

A significant property of a generalized effect algebra is that its every interval with inherited partial sum is an effect algebra. We show that in some sense the converse is also true. More precisely, we prove that a set with zero element is a generalized effect algebra if and only if all its intervals are effect algebras. We investigate inheritance of some properties from intervals to generalized effect algebras, e.g., the Riesz decomposition property, compatibility of every pair of elements, dense embedding into a complete effect algebra, to be a sub-(generalized) effect algebra, to be lattice ordered and others. The response to the Open Problem from Rie?anová and Zajac (2013) for generalized effect algebras and their sub-generalized effect algebras is given.     

The logic of Peirce algebras

Peirce algebras combine sets, relations and various operations linking the two in a unifying setting. This paper offers a modal perspective on Peirce algebras. Using modal logic a characterization of the full Peirce algebras is given, as well as a finite axiomatization of their equational theory that uses so-called unorthodox derivation rules. In addition, the expressive power of Peirce algebras is analyzed through their connection with first-order logic, and the fragment of first-order logic corresponding to Peirce algebras is described in terms of bisimulations.