Timeline for Examples where existence is harder than evaluation
Current License: CC BY-SA 4.0
25 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| May 19, 2019 at 13:38 | answer | added | Hao Chen | timeline score: 3 | |
| May 18, 2019 at 13:05 | answer | added | Pietro Majer | timeline score: 3 | |
| May 17, 2019 at 14:04 | answer | added | Richard Stanley | timeline score: 8 | |
| May 10, 2019 at 19:33 | comment | added | Ilmari Karonen | Somewhat related Q&A on Mathematics Educators: Unique candidate that fails | |
| May 10, 2019 at 4:56 | comment | added | Brevan Ellefsen | The Feynman Path Integral is a classic example of something we don't (quite) know how to describe mathematically (adequately in all cases, coming down to constructing a certain type of invariant Borel measure) but calculations are constantly done with it anyway. Physics is full of such examples. | |
| May 9, 2019 at 22:05 | vote | accept | Aryeh Kontorovich | ||
| May 9, 2019 at 18:45 | comment | added | Henry | For the combinatorial game Brussels Sprouts, Wikipedia gives a simple planar graph proof of the length of the game being $5n-2$ but does not show that the game is finite | |
| May 9, 2019 at 4:23 | answer | added | Dan Romik | timeline score: 11 | |
| May 8, 2019 at 23:54 | answer | added | Gerry Myerson | timeline score: 22 | |
| May 8, 2019 at 13:32 | history | edited | Aryeh Kontorovich | CC BY-SA 4.0 |
added 558 characters in body
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| May 8, 2019 at 12:45 | answer | added | Robert | timeline score: 12 | |
| May 8, 2019 at 11:58 | comment | added | bof | Not something I understand or know anything about (so no answer from me), but I believe the order of the monster group was evaluated well before its existence was established? | |
| May 8, 2019 at 10:31 | history | made wiki | Post Made Community Wiki by S. Carnahan♦ | ||
| May 8, 2019 at 4:29 | answer | added | David E Speyer | timeline score: 19 | |
| May 8, 2019 at 2:53 | comment | added | Gerry Myerson | It's easy to make up examples with no mathematical content. Let $X$ be any open conjecture. Let $f(x)=0$ if $x$ is an integer, otherwise let it be zero if $X$ is true, seventeen if $X$ is false. If $\lim_{x\to\infty}f(x)$ exists, it must be zero, but deciding whether it exists is equivalent to deciding $X$. | |
| May 8, 2019 at 2:44 | answer | added | Venkataramana | timeline score: 11 | |
| May 8, 2019 at 2:21 | answer | added | erz | timeline score: 37 | |
| May 8, 2019 at 2:14 | answer | added | user74900 | timeline score: 10 | |
| May 8, 2019 at 0:41 | answer | added | Gerry Myerson | timeline score: 59 | |
| May 7, 2019 at 20:59 | history | became hot network question | |||
| May 7, 2019 at 20:42 | comment | added | Christian Remling | This is most decidedly not a good one, but something like $x_{n+1}=x_n/2+1$ fits your description. Admittedly, both showing convergence and finding the limit are very easy, but if we compare the two, then finding the limit is much easier still. | |
| May 7, 2019 at 20:40 | comment | added | Aryeh Kontorovich | @ChristianRemling if you have any good ones, feel free to share! | |
| May 7, 2019 at 20:38 | comment | added | Christian Remling | Many recursions $x_{n+1}=f(x_n)$ ("find the limit") provide examples, though this is of course exactly the type of example that you give yourself. | |
| May 7, 2019 at 20:28 | answer | added | Nate Eldredge | timeline score: 45 | |
| May 7, 2019 at 20:07 | history | asked | Aryeh Kontorovich | CC BY-SA 4.0 |