Difference hierarchy
id:
difference-hierarchy-257-16615255
title:
Difference hierarchy
text:
In set theory, a branch of mathematics, the difference hierarchy over a pointclass is a hierarchy of larger pointclasses
generated by taking differences of sets. If Γ is a pointclass, then the set of differences in Γ is { A : ∃ C , D ∈ Γ } . In usual notation, this set is denoted by 2-Γ. The next level of the hierarchy is denoted by 3-Γ and consists of differences of three sets: { A : ∃ C , D , E ∈ Γ } . This definition can be extended recursively into the transfinite to α-Γ for some ordinal α.
brand slug:
wiki
category slug:
encyclopedia
description:
original url:
https://en.wikipedia.org/wiki/Difference_hierarchy
date created:
date modified:
2020-05-25T18:44:16Z
main entity:
{"identifier":"Q5275274","url":"https://www.wikidata.org/entity/Q5275274"}
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fields total:
13
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13