Timeline for Leaders and Rulers
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jun 8 at 7:48 | answer | added | James Newton | timeline score: -1 | |
| Jun 7 at 22:31 | comment | added | Alexey Birukov | @Torsten Schoeneberg Population is not empty, because there is at least a person in charge of empty group. | |
| Jun 7 at 16:13 | comment | added | Torsten Schoeneberg | Not true if the population is empty. SCNR. | |
| Jun 6 at 9:21 | comment | added | Alexey Birukov | -Who do you rule? -No one -Liar! I am the only ruler of no one! in memory of Raymond Smullyan. | |
| Jun 6 at 5:59 | history | became hot network question | |||
| Jun 6 at 0:45 | comment | added | tkf | Now it's been solved, here is the background: A few years ago I taught Cantor's diagonal argument, that any map $f\colon X\to \mathcal{P}(X)$ is not surjective. For the midterm test I thought I would set the dual task of proving that every map $g\colon \mathcal{P}(X)\to X$ is not injective. In particular I asked: $${}$$Given $g\colon \mathcal{P}(X)\to X$, find $x\in X$ and $A,B\subseteq X$, such that $x\in A, x\notin B$ and $g(A)=x=g(B)$. $${}$$ This is of course the same as the question above, if you unpack the mathematical notation. | |
| Jun 6 at 0:12 | vote | accept | tkf | ||
| Jun 5 at 23:32 | answer | added | xnor | timeline score: 22 | |
| Jun 5 at 23:27 | answer | added | azi | timeline score: 2 | |
| Jun 5 at 21:50 | history | asked | tkf | CC BY-SA 4.0 |