“Diagonal intersection”的意思、由来-开放百科全书

词条

Diagonal intersection

释义

Diagonal intersection is a term used in mathematics, especially in set theory.

If is an ordinal number and

is a sequence of subsets of , then the diagonal intersection, denoted by

is defined to be

That is, an ordinal is in the diagonal intersection if and only if it is contained in the first members of the sequence. This is the same as

where the closed interval from 0 to is used to

avoid restricting the range of the intersection.

References

Thomas Jech, Set Theory, The Third Millennium Edition, Springer-Verlag Berlin Heidelberg New York, 2003, page 92.
Akihiro Kanamori, The Higher Infinite, Second Edition, Springer-Verlag Berlin Heidelberg, 2009, page 2.

2 : Set theory|Ordinal numbers

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