MMN-3854

# Join-semilattices whose principal filters are pseudocomplemented lattices

**Ivan Chajda**, Palacky University Olomouc, Faculty of Science, Department of Algebra and Geometry, 17. listopadu 12, 771 46 Olomouc, Czech Republic,`ivan.chajda@upol.cz`

**Helmut LĂ¤nger**, TU Wien, Faculty of Mathematics and Geoinformation, Institute of Discrete Mathematics and Geometry, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria,`helmut.laenger@tuwien.ac.at`

## Abstract

This paper deals with join-semilattices whose sections, i.e. principal filters, are pseudocomplemented lattices. The pseudocomplement of a\vee b in the section [b,1] is denoted by a\rightarrow b and can be considered as the connective implication in a certain kind of intuitionistic logic. Contrary to the case of Brouwerian semilattices, sections need not be distributive lattices. This essentially allows possible applications in non-classical logics. We present a connection of the semilattices mentioned in the beginning with so-called non-classical implication semilattices which can be converted into I-algebras having everywhere defined operations. Moreover, we relate our structures to sectionally and relatively residuated semilattices which means that our logical structures are closely connected with substructural logics. We show that
I-algebras form a congruence distributive, 3-permutable and weakly regular variety.

Vol. 23 (2022), No. 2, pp. 559-577

DOI: 10.18514/MMN.2022.3854