Some Generalizations of Fedorchuk Duality Theorem -- II

TL;DR

This paper extends Fedorchuk duality to various subcategories of locally compact Hausdorff spaces, characterizing dual morphisms, and providing new insights into open and closed subsets, extensions, and compactifications.

Contribution

It generalizes Fedorchuk duality to multiple subcategories, characterizes dual morphisms, and offers new descriptions of open subsets, extensions, and compactifications in the dual framework.

Findings

Duality between DSkeLC and SkeLC categories extended to subcategories.

Characterization of LCA-embeddings and dense homeomorphic embeddings via dual morphisms.

New description of locally compact Hausdorff extensions and strengthened compactification theorems.

Abstract

As it was shown in the first part of this paper, there exists a duality between the category DSkeLC (introduced there) and the category SkeLC of locally compact Hausdorff spaces and continuous skeletal maps. We describe here the subcategories of the category DSkeLC which are dually equivalent to the following eight categories: all of them have as objects the locally compact Hausdorff spaces and their morphisms are, respectively, the injective (respectively, surjective) continuous skeletal maps, the injective (resp., surjective) open maps, the injective (resp., surjective) skeletal perfect maps, the injective (resp., surjective) open perfect maps. The particular cases of these theorems for the full subcategories of the last four categories having as objects all compact Hausdorff spaces are formulated and proved. The DSkeLC-morphisms which are LCA-embeddings and the dense homeomorphic embeddings are characterized through their dual morphisms. For any locally compact space X, a description of the frame of all open subsets of X in terms of the dual object of X is obtained. It is shown how one can build the dual object of an open subset (respectively, of a regular closed subset) of a locally compact Hausdorff space X directly from the dual object of X. Applying these results, a new description of the ordered set of all, up to equivalence, locally compact Hausdorff extensions of a locally compact Hausdorff space is obtained. Moreover, generalizing de Vries Compactification Theorem, we strengthen the Local Compactification Theorem of Leader. Some other applications are found.