Timeline for Notation for "the" left adjoint functor
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Apr 29, 2022 at 8:19 | comment | added | Jo Mo | I always use the $\flat$ and $\sharp$ notation as well, but in the exactly opposite way. It seems to make more sense to me. | |
| Feb 8, 2020 at 19:10 | comment | added | Jérôme JEAN-CHARLES | The floor is very nice and was always my prefered one. Yet (depending on the context of course) you may be willing to use the ad notation. | |
| Feb 2, 2020 at 1:29 | comment | added | Robert Furber | @WorldSEnder I think I've used this notation myself, and it comes by analogy to the fact that floor and ceiling are adjoints to the inclusion of posets $\mathbb{Z} \hookrightarrow \mathbb{R}$. | |
| Feb 1, 2020 at 23:53 | comment | added | WorldSEnder | I've seen the notation $\lceil f \rceil$ and $\lfloor f \rfloor$ being used for the isomorphism, mainly in a few comp sci papers | |
| Feb 1, 2020 at 21:11 | comment | added | Fred Rohrer | I am quite sure that the "ad"-notation does not occur in EGA outside the cited section. | |
| Feb 1, 2020 at 20:47 | comment | added | Martin Brandenburg | Let me also remark that the same section introduces a notation for the bijection $$\hom(F(x),y) \xrightarrow{\sim} \hom(x,F^{\text{ad}}(y)),$$ namely $f \mapsto f^{\flat}$, and $g \mapsto g^{\sharp}$ for the inverse. At least, this notation can be seen a lot in EGA. | |
| Feb 1, 2020 at 20:39 | comment | added | Martin Brandenburg | Yet, this leads to the question why this notation is not common, even not in EGA itself (right?). | |
| Feb 1, 2020 at 20:37 | comment | added | Martin Brandenburg | I am very happy about this answer, and I accept it right away (even though there might be other books with other notations) because EGA I has/had such a huge impact. I didn't read all of the preliminaries, so I wasn't aware that this notation is introduced there. Well spotted! | |
| Feb 1, 2020 at 20:35 | vote | accept | Martin Brandenburg | ||
| Feb 1, 2020 at 18:13 | history | answered | Fred Rohrer | CC BY-SA 4.0 |