scratch

§ Almost Universal Class

created 2022-04-28 · last edited 2023-04-02
  • A universal class is one that contains all subsets as elements.
  • A class is almost universal if every subset of LLL is a a subset of some element of LLL. But note that LLL does not need to have all subsets as elements.
  • LLL is almost universal if for any subset A⊂LA \subset LA⊂L (where AAA is a set), there is some B∈LB \in LB∈L such that A⊆BA \subseteq BA⊆B, but AAA in itself need not be in LLL.
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