Quasivarieties of Wajsberg hoops

In this paper we deal with quasivarieties of residuated structures which form the equivalent algebraic semantics of a positive frag- ment of some substructural logic. Our focus is mainly on varieties and quasivarieties of Wajsberg hoops, which are the equivalent algebraic semantics of the positive fragment of Łukasiewicz many-valued logic. In particular we study the lattice of subquasivari- eties of Wajsberg hoops and we describe completely all the subvarieties of Wajsberg hoops that are primitive. Though the treatment is mostly algebraic in nature, there are obvious connections with the underlying logic

Introducing Boolean Semilattices

We present and discuss a variety of Boolean algebras with operators that is closely related to the variety generated by all complex algebras of semilattices. We consider the problem of finding a generating set for the variety, representation questions, and axiomatizability. Several interesting subvarieties are presented. We contrast our results with those obtained for a number of other varieties generated by complex algebras of groupoids

Idempotent residuated structures : some category equivalences and their applications

This paper concerns residuated lattice-ordered idempotent commutative monoids that are subdirect products of chains. An algebra of this kind is a generalized Sugihara monoid (GSM) if it is generated by the lower bounds of the monoid identity; it is a Sugihara monoid if it has a compatible involution :. Our main theorem establishes a category equivalence between GSMs and relative Stone algebras with a nucleus (i.e., a closure operator preserving the lattice operations). An analogous result is obtained for Sugihara monoids. Among other applications, it is shown that Sugihara monoids are strongly amalgamable, and that the relevance logic RMt has the projective Beth de nability property for deduction.http://www.ams.org//journals/tran/hb201

Structural completeness in quasivarieties

In this paper we study various forms of (hereditary) structural completeness for quasivarieties of algebras, using mostly algebraic techniques. More specifically we study relative weakly projective algebras and the way they interact with structural completeness in quasivarieties. These ideas are then applied to the study of $C$-structural completeness and $C$-primitivity, through an algebraic generalization of Prucnal's substitution. Finally we study in depth dual i-discriminator quasivarieties in which a particular instance of Prucnal's substitution is used to prove that if each fundamental operation commutes with the i-discriminator, then it is primitive

Inconsistency lemmas: an algebraic approach

Treballs Finals del Màster de Lògica Pura i Aplicada, Facultat de Filosofia, Universitat de Barcelona, Curs: 2019-2020, Tutor: Ramon Jansana i Tommaso MoraschiniThe purpose of this work is to investigate what is the algebraic counterpart of the inconsistency lemma. This question already has an answer in [29]. We have only put together in this monograph all the results and concepts that are necessary to understand the whole building

Inconsistency lemmas in algebraic logic

In this paper, the inconsistency lemmas of intuitionistic and classical propositional logic are formulated abstractly. We prove that, when a (finitary) deductive system is algebraized by a variety K, then has an inconsistency lemma—in the abstract sense—iff every algebra in K has a dually pseudo-complemented join semilattice of compact congruences. In this case, the following are shown to be equivalent: (1) has a classical inconsistency lemma; (2) has a greatest compact theory and K is filtral, i.e., semisimple with EDPC; (3) the compact congruences of any algebra in K form a Boolean lattice; (4) the compact congruences of any A ∈ K constitute a Boolean sublattice of the full congruence lattice of A. These results extend to quasivarieties and relative congruences. Except for (2), they extend even to protoalgebraic logics, with deductive filters in the role of congruences. A protoalgebraic system with a classical inconsistency lemma always has a deduction-detachment theorem (DDT), while a system with a DDT and a greatest compact theory has an inconsistency lemma. The converses are false.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1521-3870hb201