Wikipedia:Reference desk/Archives/Mathematics/2023 July 18

= July 18 =

Golden ratio
Is there something wrong with the Golden ratio page? Whenever I try to access it, I get a "server timed out" error. But I can see the history log. Dhrm77 (talk) 11:50, 18 July 2023 (UTC)


 * It's working on my end; may have been a temporary error. GalacticShoe (talk) 13:48, 18 July 2023 (UTC)
 * That page timed out for me when this was originally posted, and it still times out now. Talk:Golden ratio responds normally. I tried to purge it, but although the purge prompt displayed, when I clicked 'Yes' it timed out again.
 * The history works, and there was an edit on 15 July, but the diff times out. Therefore I think something strange resulted from the last edit. By reverting that edit, I see that c. 1876 was replaced by c. 1876, which seems innocuous enough. I did not complete the reversion, in case there is more to it than meets the eye. -- Verbarson talkedits 19:31, 20 July 2023 (UTC)
 * I have re-posted this on the Help desk, as it seems to be an issue with WP rather than mathematics. -- Verbarson talkedits 19:41, 20 July 2023 (UTC)

Definitely it's behaving strangely today. Michael Hardy (talk) 22:03, 21 July 2023 (UTC)
 * OK for me right now in Australia. HiLo48 (talk) 23:27, 21 July 2023 (UTC)

Surjective variant of the pigeonhole principle
The pigeonhole principle states that if m pigeons are placed into n pigeonholes with m > n, then at least one pigeonhole must contain more than one pigeon. It is used to show that certain functions cannot be injective.

But there is also a variant of this principle that states that if m pigeons are placed into n pigeonholes with m < n, then at least one pigeonhole must be empty. It could be used to show that certain functions cannot be surjective.

Is this surjective variant of the pigeonhole principle often used compared to the injective one? GeoffreyT2000 (talk) 16:22, 18 July 2023 (UTC)


 * This sounds like a valid principle, though I don't know if it's used often enough to get a name of its own. Did you have an application in mind? --RDBury (talk) 14:42, 20 July 2023 (UTC)