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Title Bohr compactifications of algebras and structures Author info B. A. Davey, M. Haviar, H. A. Priestley Author Davey Brian A. (34%)
Co-authors Haviar Miroslav 1965- (33%) UMBFP10 - Katedra matematiky
Priestley Hilary A. (33%)
Source document Applied Categorical Structures. Vol. 25, no. 3 (2017), pp. 403-430. - Dordrecht : Springer, 2017 Person keywords Bohr Niels dánsky fyzik 1885-1962 Keywords natural duality natural extension distributive lattices Stone-Čechova kompaktifikácia - Stone-Čech compactification Language English Country Netherlands systematics 51 Annotation This paper provides a unifying framework for a range of categorical constructions characterised by universal mapping properties, within the realm of compactifications of discrete structures. Some classic examples fit within this broad picture: the Bohr compactification of an abelian group via Pontryagin duality, the zero-dimensional Bohr compactification of a semilattice, and the Nachbin order-compactification of an ordered set. The notion of a natural extension functor is extended to suitable categories of structures and such a functor is shown to yield a reflection into an associated category of topological structures. Our principal results address reconciliation of the natural extension with the Bohr compactification or its zero-dimensional variant. In certain cases the natural extension functor and a Bohr compactification functor are the same; in others the functors have different codomains but may agree on all objects. Coincidence in the stronger sense occurs in the zero-dimensional setting precisely when the domain is a category of structures whose associated topological prevariety is standard. It occurs, in the weaker sense only, for the class of ordered sets and, as we show, also for infinitely many classes of ordered structures. Coincidence results aid understanding of Bohr-type compactifications, which are defined abstractly. Ideas from natural duality theory lead to an explicit description of the natural extension which is particularly amenable for any prevariety of algebras with a finite, dualisable, generator. Examples of such classes-often varieties-are plentiful and varied, and in many cases the associated topological prevariety is standard. Public work category ADM No. of Archival Copy 39736 Database xpca - PUBLIKAČNÁ ČINNOSŤ References PERIODIKÁ-Súborný záznam periodika 
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Title Natural dualities in partnership Author info Brian A. Davey, Miroslav Haviar, Hilary A. Priestley Author Davey Brian A. (34%)
Co-authors Haviar Miroslav 1965- (33%) UMBFP10 - Katedra matematiky
Priestley Hilary A. (33%)
Source document Applied Categorical Structures. Vol. 20, no. 6 (2012), pp. 583-602. - Dordrecht : Springer, 2012 Keywords prirodzená dualita prirodzené rozšírenie kanonické rozšírenia natural duality natural extension canonical extension Language English Country Netherlands systematics 512 Public work category ADE No. of Archival Copy 23307 Catal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Database xpca - PUBLIKAČNÁ ČINNOSŤ References PERIODIKÁ-Súborný záznam periodika 
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Title Natural extensions and profinite completions of algebras Author info B. A. Davey ... [et al.] Author Davey Brian A. (25%)
Co-authors Gouveia M. J. (25%)
Haviar Miroslav 1965- (25%) UMBFP10 - Katedra matematiky
Priestley Hilary A. (25%)
Source document Algebra Universalis. Vol. 66, no. 3 (2011), pp. 205-241. - Cham : Springer Nature Switzerland AG, 2011 Keywords prirodzené rozšírenie prirodzená dualita kanonické rozšírenia profinite completion natural extension natural duality canonical extension Language English Country Switzerland systematics 51 Annotation The paper investigates profinite completions of residually finite algebras, drawing on ideas from the theory of natural dualities. Given a class A = ISP(M), where M is a set, not necessarily finite, of finite algebras, it is shown that each algebra in the class A embeds as a topologically dense subalgebra of its natural extension, and that this natural extension is isomorphic, topologically and algebraically, to the profinite completion of the original algebra. In addition it is shown how the natural extension may be concretely described as a certain family of relation-preserving maps; in the special case that M is finite and the class A possesses a single-sorted or multisorted natural duality, the relations to be preserved can be taken to be those belonging to a dualising set. For an algebra belonging to a finitely generated variety of lattice-based algebras, it is known that the profinite completion coincides with the canonical extension. In this situation the natural extension provides a new concrete realisation of the canonical extension, generalising the well-known representation of the canonical extension of a bounded distributive lattice as the lattice of up-sets of the underlying ordered set of its Priestley dual. The paper concludes with a survey of classes of algebras to which the main theorems do, and do not, apply Public work category ADE No. of Archival Copy 20292 Repercussion category VOSMAER, Jacob. Logic, algebra and topology : investigations into canonical extensions, duality theory and point-free topology. Amsterdam : Institute for Logic, Language and Computation, 2010. 255 s. ISBN 978-90-5776-214-7.
Catal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Database xpca - PUBLIKAČNÁ ČINNOSŤ References PERIODIKÁ-Súborný záznam periodika unrecognised