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Normal semicontinuous functions in pointfree topology and weak cb-frames
In a recent paper [2], we have constructed the Dedekind completion of the lattice C(L) of continuous real functions on a frame L, in terms of normal semicontinuous functions. Of course, this construction evokes the classical description of the completion of C*(X) (bounded continuous real functions on X) due to Dilworth [1], and simplified and extended to C(X) by Horn [3]. Indeed, our results extend Dilworth's construction to the pointfree setting, but we should emphasize that the pointfree situation is not merely a mimic of the classical one, what makes the whole picture more interesting.

The aim of this talk is to describe normal semicontinuous functions in pointfree topology and to introduce a class of frames which arise naturally in the study of the Dedekind completion of C(L): the weakly continuously bounded frames or weak cb-frames. We show that if L is a weak cb-frame, then the Dedekind completion of C(L) is isomorphic to some lattice of continuous functions C(M) (where M will be the Gleason cover of the given L). This is the pointfree counterpart of Proposition 4.1 in [4].
(Joint work with Javier Gutiérrez García and Jorge Picado.)

[1] R. P. Dilworth, The normal completion of the lattice of continuous functions, Trans. Amer. Math. Soc. 68, 427-438 (1950).
[2] J. Gutiérrez García, I. Mozo Carollo and J. Picado, Normal semicontinuity and the Dedekind completion of pointfree function rings, submitted.
[3] J. G. Horn, The normal completion of a subset of a complete lattice and lattices of continuous functions,  Pacific J. Math. 3, 137-152 (1953).
[4] J. E. Mack and D.G. Johnson, The Dedekind completion of C(X), Pacific J. Math. 20, 231-243 (1967).
Date:  2014-04-08
Start Time:   15:30
Speaker:  Imanol Mozo Carollo (Univ. of the Basque Country, Bilbao, Spain)
Institution:  University of the Basque Country, Bilbao, Spain
Place:  Sala 5.5
Research Groups: -Algebra, Logic and Topology
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