Ultrafilters and mappings
The following types of continuous functions between completely regular spaces are considered: closed, quasi-perfect, d-, \(d^*\)-, d'-, sd-, sd'-, nd-cp-, \(d_ 1\)-, \(d_ 2\)-, *-open, Z-, WZ-, \(W^*\)-open, N-, WN-, \(W_ rN\)-, hyper-real. For the most types, a characterization in terms of closed or open ultrafilters is given. There are also stated some possible relationships between those functions and various properties of generalized realcompact spaces.
characterization of maps by closed (open) ultrafilters
scientific article; zbMATH DE number 3846432