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- Pretopological_space abstract "In general topology, a pretopological space is a generalization of the concept of topological space. A pretopological space can be defined as in terms of either filters or a preclosure operator.The similar, but more abstract, notion of a Grothendieck pretopologyis used to form a Grothendieck topology, and is covered in thearticle on that topic. Let X be a set. A neighborhood system for a pretopology on X is a collection of filters N(x), one for each element of X such that every set in N(x) contains x as a member. Each element of N(x) is called a neighborhood of x. A pretopological space is then a set equipped with such a neighborhood system.A net xα converges to a point x in X if xα is eventually in every neighborhood of x.A pretopological space can also be defined as (X, cl ), a set X with a preclosure operator (Čech closure operator) cl. The two definitions can be shown to be equivalent as follows: define the closure of a set S in X to be the set of all points x such that some net that converges to x is eventually in S. Then that closure operator can be shown to satisfy the axioms of a preclosure operator. Conversely, let a set S be a neighborhood of x if x is not in the closure of the complement of S. The set of all such neighborhoods can be shown to be a neighborhood system for a pretopology.A pretopological space is a topological space when its closure operator is idempotent.A map f : (X, cl ) → (Y, cl' ) between two pretopological spaces is continuous if it satisfies for all subsets A of X: f (cl (A)) ⊆ cl' (f (A)) .".
- Pretopological_space wikiPageExternalLink 01-02-011.pdf.
- Pretopological_space wikiPageID "2071260".
- Pretopological_space wikiPageLength "2396".
- Pretopological_space wikiPageOutDegree "8".
- Pretopological_space wikiPageRevisionID "505944816".
- Pretopological_space wikiPageWikiLink Category:General_topology.
- Pretopological_space wikiPageWikiLink Filter_(mathematics).
- Pretopological_space wikiPageWikiLink General_topology.
- Pretopological_space wikiPageWikiLink Grothendieck_topology.
- Pretopological_space wikiPageWikiLink Idempotence.
- Pretopological_space wikiPageWikiLink Idempotent.
- Pretopological_space wikiPageWikiLink Net_(mathematics).
- Pretopological_space wikiPageWikiLink Preclosure_operator.
- Pretopological_space wikiPageWikiLink Čech_closure_operator.
- Pretopological_space wikiPageWikiLinkText "Pretopological space".
- Pretopological_space wikiPageWikiLinkText "pretopological space".
- Pretopological_space hasPhotoCollection Pretopological_space.
- Pretopological_space subject Category:General_topology.
- Pretopological_space hypernym Generalization.
- Pretopological_space comment "In general topology, a pretopological space is a generalization of the concept of topological space. A pretopological space can be defined as in terms of either filters or a preclosure operator.The similar, but more abstract, notion of a Grothendieck pretopologyis used to form a Grothendieck topology, and is covered in thearticle on that topic. Let X be a set.".
- Pretopological_space label "Pretopological space".
- Pretopological_space sameAs m.06k4xn.
- Pretopological_space sameAs Q7242162.
- Pretopological_space sameAs Q7242162.
- Pretopological_space wasDerivedFrom Pretopological_space?oldid=505944816.
- Pretopological_space isPrimaryTopicOf Pretopological_space.