Vol. 104, No. 2, 1983

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Ultrafilters and mappings

Takesi Isiwata

Vol. 104 (1983), No. 2, 371–389
Abstract

We give characterizations of closed, quasi-perfect, d-, Z-, WZ-, W-open, N-, WN-, WrN- and other maps using closed or open ultrafilters and investigate relations between these maps and various properties as generalizations of realcompactness, i.e., almost-, a-, c- and wa-real compactness, cb-ness and weak cb-ness. Finally we establish several theorems about the perfect W-open image of a weak cb space and its application to the absolute E(X) of a given space X.

Mathematical Subject Classification 2000
Primary: 54C10
Secondary: 54D30
Milestones
Received: 21 April 1981
Revised: 5 August 1981
Published: 1 February 1983
Authors
Takesi Isiwata