In topology, a preclosure operator or Čech closure operator is a map between subsets of a set, similar to a topological closure operator, except that it...

conceptPages displaying wikidata descriptions as a fallback Preclosure operator – Closure operator Diatta, Jean (2009-11-14). "On critical sets of a finite...

family of functions f φ {\displaystyle f_{\varphi }} gives rise to a preclosure operator F {\displaystyle F} on the power set of M {\displaystyle M} F ( A...

pseudosemimetric, i.e. a symmetric premetric. Any premetric gives rise to a preclosure operator c l {\displaystyle cl} as follows: c l ( A ) = { x | d ( x , A )...

realsPages displaying wikidata descriptions as a fallback Preclosure operator – Closure operator Pretopological space – Generalized topological space Topological...

{scl} (\operatorname {scl} (S)).} That is, sequential closure is a preclosure operator. Unlike topological closure, sequential closure is not idempotent:...

pretopological space can be defined in terms of either filters or a preclosure operator. The similar, but more abstract, notion of a Grothendieck pretopology...