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Algebra of sets
editI would like to know what is the symbol for the null set. It is NOT put here, the null sign? ø? — Preceding unsigned comment added by 79.151.77.164 (talk) 07:02, 24 May 2023 (UTC)
The following was removed from the lede today as it is unreferenced.
- More generally, whenever an ideal is taken as understood, then a null set is any element of that ideal.
There is only one reference at Ideal (set theory), and mention there of "null set" is also unreferenced. If this meaning of the term can be established at that article, then an appropriate WP:Hatnote may be placed in this article. — Rgdboer (talk) 22:57, 10 November 2015 (UTC)
- Hmm, fair enough on the sourcing. I'm not sure where to find a specific reference.
- I don't know why you'd want a hatnote, though. It's not a different concept, just a more general version of the same one, since the null sets of any complete measure form an ideal. --Trovatore (talk) 02:59, 11 November 2015 (UTC)
Haar null set
editThe wording of § Haar null seems to vacillate between Banach spaces in the first paragraph and topological groups in the third. A separable Banach space is a special case of a complete metric group. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 10:27, 13 September 2024 (UTC)