15 research outputs found
On functions preserving regular semimetrics and quasimetrics satisfying the relaxed polygonal inequality
Rings of maps: sequential convergence and completion
summary:The ring of all real-valued measurable functions, carrying the pointwise convergence, is a sequential ring completion of the subring of all continuous functions and, similarly, the ring of all Borel measurable subsets of is a sequential ring completion of the subring of all finite unions of half-open intervals; the two completions are not categorical. We study -rings of maps and develop a completion theory covering the two examples. In particular, the -fields of sets form an epireflective subcategory of the category of fields of sets and, for each field of sets , the generated -field yields its epireflection. Via zero-rings the theory can be applied to completions of special commutative -groups