Talk:Universe (mathematics)
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Weirdness
A former version of this article was rather weird, and nobody understood it: so it was nominated for deletion, until Toby Bartels saved the day. Three cheers for Toby! :)
- Gosh, thanks. ^_^ -- Toby Bartels
From the deletion nomination:
- A mathematician should look at this - it seems like oddball city to me. --mav 04:56, 15 Aug 2003 (UTC)
- I am a mathematician, and I agree [with deletion]. I believe it was written in good faith and that it took real effort but that it doesn't belong in the wikipedia. Michael Larsen 10:36, 15 Aug 2003 (UTC)
- makes absolutely no sense to me. seems like disinformation --Alex.tan 06:29, 15 Aug 2003 (UTC)
- Typical quackpot ramble. Andre Engels 10:47, 15 Aug 2003 (UTC)
- Nonsense - delete it. This should contain an entry on the set-theoretical term "Universe". -- Schnee 23:33, 16 Aug 2003 (UTC) (mathematician)
- I think that I've got a good start on a real article there now. BTW, some of that old stuff actually some sense in it too, but well buried under the overenthusiasm, lack of precision, and POV. Look up Douglas Sweetser on the Internet if you want to see more of it; or look up David Hestenes in the library if you want something similar but sensible. -- Toby Bartels 14:33, 21 Aug 2003 (UTC)
Notation
power set notation: is it clearer to write PX or P(X) ? Martin
I prefer the simplicity of "PX". Actually, I really like
- <math> \mathcal{P}X \! <math>,
but that would be unnecessary dependence on images IMO. I would hope that "PX" is confusing only to those poor benighted souls that believe that function application is always denoted by parentheses, but a little reflection on one's days in trigonometry can usually cure that. To be sure, there's nothing at all wrong with "P(X)", and I would hardly change an article that already used such notation! -- Toby Bartels 07:20, 24 Aug 2003 (UTC)
For "poor benighted souls", read "programmers" :)
I'll leave it be. Martin
In case anybody in the future decides to change it, note that the notations PX and SX are serving largely analogous roles. So their markups should be similar. (Similarly, the subscripts in SiX, Li, and Vi are analogous.) -- Toby Bartels 19:59, 28 Jan 2004 (UTC)
I have some questions about set universes. I can construct a set universe starting from any give set, right? The last sentences of the set theory section tell me that I will always get the standard set universe (starting with {}). Is that right? As far as I know, the power class of a class X is defined to be the class of all subsets of X. If this is so, what is the power class of the set universe? Is it the universe itself? --SirJective (217.80.240.75 20:36, 4 May 2004 (UTC))