Open AccessClosed ideals in the functionally countable subalgebra of C(X)
Author(s) -
Amir Veisi
Publication year - 2022
Publication title -
applied general topology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.638
H-Index - 13
eISSN - 1989-4147
pISSN - 1576-9402
DOI - 10.4995/agt.2022.15844
Subject(s) - ultrafilter , mathematics , ideal (ethics) , countable set , subalgebra , maximal ideal , second countable space , topology (electrical circuits) , closed set , intersection (aeronautics) , space (punctuation) , boolean prime ideal theorem , zero (linguistics) , discrete mathematics , combinatorics , pure mathematics , algebra over a field , prime (order theory) , philosophy , linguistics , epistemology , engineering , aerospace engineering
In this paper, closed ideals in Cc(X), the functionally countable subalgebra of C(X), with the mc-topology, is studied. We show that ifX is CUC-space, then C*c(X) with the uniform norm-topology is a Banach algebra. Closed ideals in Cc(X) as a modified countable analogue of closed ideals in C(X) with the m-topology are characterized. For a zero-dimensional space X, we show that a proper ideal in Cc(X) is closed if and only if it is an intersection of maximal ideals of Cc(X). It is also shown that every ideal in Cc(X) with the mc-topology is closed if and only if X is a P-space if and only if every ideal in C(X) with the m-topology is closed. Moreover, for a strongly zero-dimensional space X, it is proved that a properly closed ideal in C*c(X) is an intersection of maximal ideals of C*c(X) if and only if X is pseudo compact. Finally, we show that if X is a P-space and F is an ec-filter on X, then F is an ec-ultrafilter if and only if it is a zc-ultrafilter.