110 research outputs found
Finite closed coverings of compact quantum spaces
We show that a projective space P^\infty(Z/2) endowed with the Alexandrov
topology is a classifying space for finite closed coverings of compact quantum
spaces in the sense that any such a covering is functorially equivalent to a
sheaf over this projective space. In technical terms, we prove that the
category of finitely supported flabby sheaves of algebras is equivalent to the
category of algebras with a finite set of ideals that intersect to zero and
generate a distributive lattice. In particular, the Gelfand transform allows us
to view finite closed coverings of compact Hausdorff spaces as flabby sheaves
of commutative C*-algebras over P^\infty(Z/2).Comment: 26 pages, the Teoplitz quantum projective space removed to another
paper. This is the third version which differs from the second one by fine
tuning and removal of typo
Algebraic description of spacetime foam
A mathematical formalism for treating spacetime topology as a quantum
observable is provided. We describe spacetime foam entirely in algebraic terms.
To implement the correspondence principle we express the classical spacetime
manifold of general relativity and the commutative coordinates of its events by
means of appropriate limit constructions.Comment: 34 pages, LaTeX2e, the section concerning classical spacetimes in the
limit essentially correcte
D-completions and the d-topology
In this article we give a general categorical construction via reflection functors for various completions of T0-spaces subordinate to sobrification, with a particular emphasis on what we call the D-completion, a type of directed completion introduced by Wyler [O. Wyler, Dedekind complete posets and Scott topologies, in: B. Banaschewski, R.-E. Hoffmann (Eds.), Continuous Lattices Proceedings, Bremen 1979, in: Lecture Notes in Mathematics, vol. 871, Springer Verlag, 1981, pp. 384-389]. A key result is that all completions of a certain type are universal, hence unique (up to homeomorphism). We give a direct definition of the D-completion and develop its theory by introducing a variant of the Scott topology, which we call the d-topology. For partially ordered sets the D-completion turns out to be a natural dcpo-completion that generalizes the rounded ideal completion. In the latter part of the paper we consider settings in which the D-completion agrees with the sobrification respectively the closed ideal completion. © 2008 Elsevier B.V. All rights reserved
-quasicontinuous spaces
In this paper, as a common generalization of -continuous spaces and
-quasicontinuous posets, we introduce the concepts of
-quasicontinuous spaces and -convergence of nets for
arbitrary topological spaces by the cuts. Some characterizations of
-quasicontinuity of spaces are given. The main results are: (1) a space
is -quasicontinuous if and only if its weakly irreducible topology is
hypercontinuous under inclusion order; (2) A space is
-quasicontinuous if and only if the -convergence in
is topological
Completely Precontinuous Posets
AbstractIn this paper, concepts of strongly way below relations, completely precontinuous posets, coprimes and Heyting posets are introduced. The main results are: (1) The strongly way below relations of completely precontinuous posets have the interpolation property; (2) A poset P is a completely precontinuous poset iff its normal completion is a completely distributive lattice; (3) An ω-chain complete P is completely precontinuous iff P and Pop are precontinuous and its normal completion is distributive iff P is precontinuous and has enough coprimes; (4) A poset P is completely precontinuous iff the strongly way below relation is the smallest approximating auxiliary relation on P iff P is a Heyting poset and there is a smallest approximating auxiliary relation on P. Finally, given a poset P and an auxiliary relation on P, we characterize those join-dense subsets of P whose strongly way-below relation agrees with the given auxiliary relation
Web spaces and worldwide web spaces: Topological aspects of domain theory
Web spaces, wide web spaces and worldwide web spaces (alias C-spaces) provide useful generalizations of continuous domains. We present new characterizations of such spaces and their patch spaces, obtained by joining the original topology with a second topology having the dual specialization order; these patch spaces possess good convexity and separation properties and determine the original web spaces. The category of C-spaces is concretely isomorphic to the category of fan spaces; these are certain quasi-ordered spaces having neighborhood bases of fans, where a fan is obtained by deleting a finite number of principal dual ideals from a principal dual ideal. Our approach has useful consequences for domain theory, because the T0 web spaces are exactly the generalized Scott spaces associated with locally approximating ideal extensions, and the T0 C-spaces are exactly the generalized Scott spaces associated with globally approximating and interpolating ideal extensions. The characterization of continuous lattices as meet-continuous lattices with T2 Lawson topology and the Fundamental Theorem of Compact Semilattices are extended to non-complete posets. Finally, cardinal invariants like density and weight of the involved objects are investigated. © 2019 Marcel Erné. All rights reserved
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