arXiv subjects

Adam Přenosil

Publications and source records attributed to Adam Přenosil.

18 recordsLinked to original sources

arXiv2026

Sequent calculi for first-order ST

Strict-Tolerant Logic (ST) underpins naive theories of truth and vagueness (respectively including a fully disquotational truth predicate and an unrestricted tolerance principle) without jettisoning any classically valid laws. The classical sequent calculus without Cut is sometimes advocated as an appropriate proof-theoretic presentation of ST. Unfortunately, there is only a partial correspondence between its derivability relation and the relation of local metainferential ST-validity - these relations coincide only upon the addition of elimination rules and only within the propositional fragment of the calculus, due to the non-invertibility of the quantifier rules. In this paper, we present two calculi for first-order ST with an eye to recapturing this correspondence in full. The first calculus is close in spirit to the Epsilon calculus. The other calculus includes rules for the discharge of sequent-assumptions; moreover, it is normalisable and admits interpolation.

math.LO↗

arXiv2025

Balanced residuated partially ordered semigroups

A residuated semigroup is a structure $\langle A,\le,\cdot,\backslash,/ \rangle$ where $\langle A,\le \rangle$ is a poset and $\langle A,\cdot \rangle$ is a semigroup such that the residuation law $x\cdot y\le z\iff x\le z/y\iff y\le x \backslash z$ holds. An element $p$ is positive if $a\le pa$ and $a \le ap$ for all $a$. A residuated semigroup is called balanced if it satisfies the equation $x \backslash x \approx x / x$ and moreover each element of the form $a \backslash a = a / a$ is positive, and it is called integrally closed if it satisfies the same equation and moreover each element of this form is a global identity. We show how a wide class of balanced residuated semigroups (so-called steady residuated semigroups) can be decomposed into integrally closed pieces, using a generalization of the classical Plonka sum construction. This generalization involves gluing a disjoint family of ordered algebras together using multiple families of maps, rather than a single family as in ordinary Plonka sums.

cs.LO↗

arXiv2025

Nagata products of bimodules over residuated lattices

We study the (restricted) Nagata product construction, which produces a partially ordered semigroup from a bimodule consisting of a partially ordered semigroup acting on a (pointed) join semilattice. A canonical example of such a bimodule is given by a residuated lattice acting on itself by division, in which case the Nagata product coincides with the so-called twist product of the residuated lattice. We show that, given some further structure, a pointed bimodule can be reconstructed from its restricted Nagata product. This yields an adjunction between the category of cyclic pointed residuated bimodules and a certain category of posemigroups with additional structure, which subsumes various known adjunctions involving the twist product construction.

math.LO↗

arXiv2025

Duality for finitely valued algebras

The theory of natural dualities provides a well-developed framework for studying Stone-like dualities induced by an algebra $\mathbf{L}$ which acts as a dualizing object when equipped with suitable topological and relational structure. The development of this theory has, however, largely remained restricted to the case where $\mathbf{L}$ is finite. Motivated by the desire to provide a universal algebraic formulation of the existing duality of Cignoli and Marra or locally weakly finite MV-algebras and to extend it to a corresponding class of positive MV-algebras, in this paper we investigate Stone-like dualities where the algebra $\mathbf{L}$ is allowed to be infinite. This requires restricting our attention from the whole prevariety generated by $\mathbf{L}$ to the subclass of algebras representable as algebras of $\mathbf{L}$-valued functions of finite range, a distinction that does not arise in the case of finite $\mathbf{L}$. Provided some requirements on $\mathbf{L}$ are met, our main result establishes a categorical duality for this class of algebras, which covers the above cases of MV-algebras and positive MV-algebras.

math.LO↗

arXiv2024

On the structure of balanced residuated partially ordered monoids

A residuated poset is a structure $\langle A,\le,\cdot,\backslash,/,1 \rangle$ where $\langle A,\le \rangle$ is a poset and $\langle A,\cdot,1 \rangle$ is a monoid such that the residuation law $x\cdot y\le z\iff x\le z/y\iff y\le x\backslash z$ holds. A residuated poset is balanced if it satisfies the identity $x\backslash x \approx x/x$. By generalizing the well-known construction of Plonka sums, we show that a specific class of balanced residuated posets can be decomposed into such a sum indexed by the set of positive idempotent elements. Conversely, given a semilattice directed system of residuated posets equipped with two families of maps (instead of one, as in the usual case), we construct a residuated poset based on the disjoint union of their domains. We apply this approach to provide a structural description of some varieties of residuated lattices and relation algebras.

math.LO↗

arXiv2024

Equivalence of multiset-based consequence relations

The pioneering work of Blok and J\'onsson and its further development by Galatos and Tsinakis initiated an abstract study of consequence relations using the tools of module theory, where consequence relations over all types of syntactic objects are put on an equal footing. However, the assumption that in a consequence relation the premises form merely a set, as opposed to a more complicated structure, is still retained. An attempt to extend this framework to account for inferentially substructural generalizations of consequence relations, where the premises have the structure of a finite multiset, was recently made by Cintula, Gil-F\'erez, Moraschini, and Paoli. In this paper, we develop a different inferentially substructural generalization of the work of Galatos and Tsinakis, where we instead assume that the premises have the structure of a set of finite multisets. This leads a somewhat smoother framework which, unlike that of Cintula et al., covers the original theory of Galatos and Tsinakis as a special case.

math.LO↗

arXiv2024

Levin's and Prucnal's theorems on Medvedev's logic of finite problems

The purpose of this note is to provide a transparent and unified retelling of both Skvortsov's proof of the structural completeness of Medvedev's logic of finite problems, which is a classical result originally due to Prucnal, and of Levin's proof that Medvedev's logic of finite problems is the largest extension of the (weak) Kreisel-Putnam logic with the disjunction property. Presenting both results together allows us to simplify their presentation, as they both hinge on the same lemma. There is no novel content in this note, its purpose is merely to present the material in a more accessible way.

math.LO↗

arXiv2024

Equational definitions of logical filters

A finitary propositional logic can be given an algebraic reading in two different ways: by translating formulas into equations and logical rules into quasi-equations, or by translating logical rules directly into equations. The former type of algebraic interpretation has been extensively studied and underlies the theory of algebraization. Here we shall develop a systematic theory of the latter type of algebraic interpretation. More precisely, we consider a semantic form of this property which we call the equational definability of compact filters (EDCF). Paralleling the well-studied hierarchy of variants of the deduction--detachment theorem (DDT), this property also comes in local, parametrized, and parametrized local variants. Our main results give a semantic characterization of each of these variants of the EDCF in a spirit similar to the existing characterizations of the DDT. While the EDCF hierarchy and the DDT hierarchy coincide for algebraizable logics, part of the interest of the EDCF stems from the fact it is often enjoyed even by logics which are not well-behaved in terms of other existing classifications in algebraic logic.

math.LO↗

arXiv2023

Compatibility between modal operators in distributive modal logic

Unlike in classical modal logic, in non-classical modal logics the box and diamond operators frequently fail to be interdefinable. Instead, these logics impose some compatibility conditions which tie the box and diamond operators together and ensure that in terms of Kripke semantics they arise from the same accessibility relation. This is, for instance, the case in the intuitionistic modal logic of Fischer Servi and the positive modal logic of Dunn. In these logics, however, such compatibility conditions also impose further conditions on the accessibility relation. In this paper, we identify the basic compatibility conditions which ensure that modal operators in distributive modal logics arise from a single accessibility relation without imposing any restrictions on the relation. As in the distributive logic of Gehrke, Nagahashi, and Venema, we allow for negative box and diamond operators here in addition to the usual positive ones. Intuitionistic modal logic and positive modal logic, or more precisely the corresponding classes of algebras, are then obtained in a modular way by adding certain canonical axioms which we call locality conditions on top of these basic compatibility conditions.

math.LO↗

arXiv2023

Pointed lattice subreducts of varieties of residuated lattices

We study the pointed lattice subreducts of varieties of residuated lattices (RLs) and commutative residuated lattices (CRLs), i.e. lattice subreducts expanded by the constant 1 denoting the multiplicative unit. Given any positive universal class of pointed lattices K satisfying a certain equation, we describe the pointed lattice subreducts of semi-K and of pre-K RLs and CRLs. The quasivariety of semi-prime-pointed lattices generated by pointed lattices with a join prime constant 1 plays an important role here. In particular, the pointed lattices reducts of integral (semiconic) RLs and CRLs are precisely the integral (semiconic) semi-prime-pointed lattices. We also describe the pointed lattice subreducts of integral cancellative CRLs, proving in \mbox{particular} that every lattice is a subreduct of some integral cancellative CRL. This resolves an open problem about cancellative CRLs.

math.LO↗

arXiv2021

Logics of upsets of De Morgan lattices

We study logics determined by matrices consisting of a De~Morgan lattice with an upward closed set of designated values, such as the logic of non-falsity preservation in a given finite Boolean algebra and Shramko's logic of non-falsity preservation in the four-element subdirectly irreducible De Morgan lattice. The key tool in the study of these logics is the lattice-theoretic notion of an $n$-filter. We study the logics of all (complete, consistent, and classical) $n$-filters on De Morgan lattices, which are non-adjunctive generalizations of the four-valued logic of Belnap and Dunn (of the three-valued logics of Priest and Kleene, and of classical logic). We then show how to find a finite Hilbert-style axiomatization of any logic determined by a finite family of prime upsets of finite De Morgan lattices and a finite Gentzen-style axiomatization of any logic determined by a finite family of filters on finite De Morgan lattices. As an application, we axiomatize Shramko's logic of anything but falsehood.

math.LO↗

arXiv2021

Complemented MacNeille completions and algebras of fractions

We introduce ($\ell$-)bimonoids as ordered algebras consisting of two compatible monoidal structures on a partially ordered (lattice-ordered) set. Bimonoids form an appropriate framework for the study of a general notion of complementation, which subsumes both Boolean complements in bounded distributive lattices and multiplicative inverses in monoids. The central question of the paper is whether and how bimonoids can be embedded into complemented bimonoids, generalizing the embedding of cancellative commutative monoids into their groups of fractions and of bounded distributive lattices into their free Boolean extensions. We prove that each commutative ($\ell$-)bimonoid indeed embeds into a complete complemented commutative $\ell$-bimonoid in a doubly dense way reminiscent of the Dedekind--MacNeille completion. Moreover, this complemented completion, which is term equivalent to a commutative involutive residuated lattice, sometimes contains a tighter complemented envelope analogous to the group of fractions. In the case of cancellative commutative monoids this algebra of fractions is precisely the familiar group of fractions, while in the case of Brouwerian (Heyting) algebras it is a (bounded) idempotent involutive commutative residuated lattice. This construction of the algebra of fractions in fact yields a categorical equivalence between varieties of integral and of involutive residuated structures which subsumes as special cases the known equivalences between Abelian $\ell$-groups and their negative cones, and between Sugihara monoids and their negative cones.

math.LO↗

arXiv2021

Filter classes of upsets of distributive lattices

Let us say that a class of upward closed sets (upsets) of distributive lattices is a finitary filter class if it is closed under homomorphic preimages, intersections, and directed unions. We show that the only finitary filter classes of upsets of distributive lattices are formed by what we call $n$-filters. These are related to the finite Boolean lattice with $n$ atoms in the same way that filters are related to the two-element Boolean lattice: $n$-filters are precisely the intersections of prime $n$-filters and prime $n$-filters are precisely the homomorphic preimages of the prime $n$-filter of non-zero elements of the finite Boolean lattice with $n$ atoms. Moreover, $n$-filters on Boolean algebras are the only finitary filter classes of upsets of Boolean algebras generated by prime upsets.

math.LO↗

arXiv2021

The lattice of super-Belnap logics

We study the lattice of extensions of four-valued Belnap--Dunn logic, called super-Belnap logics by analogy with superintuitionistic logics. We describe the global structure of this lattice by splitting it into several subintervals, and prove some new completeness theorems for super-Belnap logics. The crucial technical tool for this purpose will be the so-called antiaxiomatic (or explosive) part operator. The antiaxiomatic (or explosive) extensions of Belnap--Dunn logic turn out to be of particular interest owing to their connection to graph theory: the lattice of finitary antiaxiomatic extensions of Belnap--Dunn logic is iso\-morphic to the lattice of upsets in the homomorphism order on finite graphs (with loops allowed). In particular, there is a continuum of finitary super-Belnap logics. Moreover, a non-finitary super-Belnap logic can be constructed with the help of this isomorphism. As algebraic corollaries we obtain the existence of a continuum of antivarieties of De Morgan algebras and the existence of a prevariety of De Morgan algebras which is not a quasivariety.

math.LO↗

arXiv2021

From partially ordered monoids to partially ordered groups via free nuclear preimages

Two fundamental constructions operating on residuated lattices and partially ordered monoids (pomonoids) are so-called nuclear images and conuclear images. Nuclear images allow us to construct many of the ordered algebras which arise in non-classical logic (such as pomonoids, semilattice-ordered monoids, and residuated lattices) from cancellative ones. Conuclear images then allow us to construct some of these cancellative algebras from partially ordered or lattice-ordered groups. Among other things, we show that finite (commutative) integral residuated lattices are precisely the finite nuclear images of commutative cancellative integral residuated lattices and that (commutative) integrally closed pomonoids are precisely the nuclear images of subpomonoids of partially ordered (Abelian) groups. The key construction is the free nuclear preimage of a pomonoid. As a by-product of our study of free nuclear preimages, we obtain a syntactic characterization of quasivarieties of pomonoids and semilattice-ordered monoids closed under nuclear images.

math.LO↗

arXiv2021

De Morgan clones and four-valued logics

We study clones on a four-element set related to the clone $\mathsf{DMA}$ of all term functions of the sub\-directly irreducible four-element De~Morgan algebra $\mathbf{DM_{4}}$. We find generating sets for the clones of all functions preserving the subalgebras of $\mathbf{DM_{4}}$, the auto\-morphisms of~$\mathbf{DM_{4}}$, the truth order and the information order on $\mathbf{DM_{4}}$, as well as clones defined by conjunctions of these conditions. We identify the covers of $\mathsf{DMA}$ in the lattice of four-valued clones and describe the lattice of clones above $\mathsf{DMA}$ which contain the discriminator function. Finally, observing that each clone above $\mathsf{DMA}$ defines an expansion of the four-valued Belnap--Dunn logic, we classify these clones by their metalogical properties, specifically by their position within the Leibniz and Frege hierarchies of abstract algebraic logic.

math.LO↗

arXiv2021

Four-valued logics of truth, non-falsity, exact truth, and material equivalence

The four-valued semantics of Belnap--Dunn logic, consisting of the truth values True, False, Neither, and Both, gives rise to several non-classical logics depending on which feature of propositions we wish to preserve: truth, non-falsity, or exact truth (truth and non-falsity). Interpreting equality of truth values in this semantics as material equivalence of propositions, we can moreover see the equational consequence relation of this four-element algebra as a logic of material equivalence. In this paper we axiomatize all combinations of these four-valued logics, for example the logic of truth and exact truth or the logic of truth and material equivalence. These combined systems are consequence relations which allow us to express implications involving more than one of these features of propositions.

math.LO↗

arXiv2021

Semisimplicity, Glivenko theorems, and the excluded middle

We formulate a general, signature-independent form of the law of the excluded middle and prove that a logic is semisimple if and only if it enjoys this law, provided that it satisfies a weak form of the so-called inconsistency lemma of Raftery. We then show that this equivalence can be used to provide simple syntactic proofs of the theorems of Kowalski and Kracht characterizing the semisimple varieties of FLew-algebras and Boolean algebras with operators, and to extend them to FLe-algebras and Heyting algebras with operators. Moreover, under stronger assumptions this correspondence works at the level of individual models: the semisimple models of such a logic are precisely those which satisfy an axiomatic form of the law of the excluded middle, and a Glivenko-like connection obtains between the logic and its extension by the axiom of the excluded middle. This in particular subsumes the well-known Glivenko theorems relating intuitionistic and classical logic and the modal logics S4 and S5. As a consequence, we also obtain a description of the subclassical substructural logics which are Glivenko related to classical logic.

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