Varieties of positive modal algebras and structural completeness
Logic
2019-08-06 v1
Abstract
Positive modal algebras are the positive-subreducts of modal algebras. We prove that the variety of positive S4-algebras is not locally finite. On the other hand, the free one-generated positive S4-algebra is shown to be finite. Moreover, we describe the bottom part of the lattice of varieties of positive S4-algebras. Building on this, we characterize (passively, hereditarily) structurally complete varieties of positive K4-algebras.
Cite
@article{arxiv.1908.01659,
title = {Varieties of positive modal algebras and structural completeness},
author = {T. Moraschini},
journal= {arXiv preprint arXiv:1908.01659},
year = {2019}
}