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JOURNALS // Algebra and Discrete Mathematics // Archive

Algebra Discrete Math., 2018 Volume 25, Issue 1, Pages 39–55 (Mi adm643)

This article is cited in 1 paper

RESEARCH ARTICLE

Construction of a complementary quasiorder

Danica Jakubíková-Studenovská, Lucia Janičková

Institute of Mathematics, P.J. Šafárik University, Jesenná 5, 041 54 Košice, Slovak Republic

Abstract: For a monounary algebra $\mathcal{A}=(A,f)$ we study the lattice $\operatorname{Quord}\mathcal{A}$ of all quasiorders of $\mathcal{A}$, i.e., of all reflexive and transitive relations compatible with $f$. Monounary algebras $(A, f)$ whose lattices of quasiorders are complemented were characterized in 2011 as follows: ($*$) $f(x)$ is a cyclic element for all $x \in A$, and all cycles have the same square-free number $n$ of elements. Sufficiency of the condition ($*$) was proved by means of transfinite induction. Now we will describe a construction of a complement to a given quasiorder of $(A, f)$ satisfying ($*$).

Keywords: monounary algebra, quasiorder, lattice, complement, complemented lattice.

MSC: 08A60, 08A02

Received: 02.11.2016
Revised: 28.08.2017

Language: English



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