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Optimal natural dualities: the role of endomorphisms

Published online by Cambridge University Press:  09 April 2009

M. J. Saramago
Affiliation:
Departmento de Matemática, Faculdade de Ciências, Universidade de Lisboa, 1749–016 Lisboa, Portugal e-mail: [email protected] Centro de Álgebra, Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649–003 Lisboa, Portugal
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Abstract

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The optimality of dualities on a quasivariety , generated by a finite algebra , has been introduced by Davey and Priestley in the 1990s. Since every optimal duality is determined by a transversal of a certain family of subsets of Ω, where Ω is a given set of relations yielding a duality on , an understanding of the structures of these subsets—known as globally minimal failsets—was required. A complete description of globally minimal failsets which do not contain partial endomorphisms has recently been given by the author and H. A. Priestley. Here we are concerned with globally minimal failsets containing endomorphisms. We aim to explain what seems to be a pattern in the way endomorphisms belong to these failsets. This paper also gives a complete description of globally minimal failsets whose minimal elements are automorphisms, when is a subdirectly irreducible lattice-structured algebra.

Type
Research Article
Copyright
Copyright © Australian Mathematical Society 2004

References

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