Congruence Preservation, Lattices and Recognizability

TL;DR

This paper generalizes congruence preserving functions in algebras, characterizing them via stability under inverse images of Boolean algebras and lattices generated from recognizable subsets, extending prior results.

Contribution

It introduces a generalized notion of stable functions in algebras, linking congruence preservation to recognizability and Boolean algebra structures, broadening previous frameworks.

Findings

Characterization of functions via Boolean algebra stability

Extension to finite index congruences and recognizable subsets

Diagrammatic visualization of the algebraic structures

Abstract

We study in general algebras Gratzer's notion of congruence preserving function, characterizing functions in terms of stability under inverse image of particular Boolean algebras of subsets generated from any subset of the algebra. Weakening Gratzer's notion to only finite index congruences, a similar result holds with lattices of sets. Genereralizing the notion to that of stable preorder preserving function, we extend these characterizations to Boolean algebras and lattices generated from any recognizable subset of the algebra. Our starting point is a result with related flavor on the additive algebra of natural integers which was obtained some years ago. All these results can be visualized in the diagram of Table 1. We finally consider some simple particular conditions on the algebra allowing to get a richer diagram.