Timeline for The fundamental groupoid and a pushout in the category of groupoids.
Current License: CC BY-SA 3.0
11 events
| when toggle format | what | by | license | comment | |
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| Jun 15, 2020 at 7:27 | history | edited | CommunityBot |
Commonmark migration
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| Mar 10, 2017 at 9:42 | history | edited | CommunityBot |
replaced http://upload.wikimedia.org/ with https://upload.wikimedia.org/
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| Nov 25, 2011 at 11:35 | answer | added | Ronnie Brown | timeline score: 4 | |
| Sep 12, 2011 at 17:21 | answer | added | Ronnie Brown | timeline score: 5 | |
| Sep 5, 2011 at 21:49 | vote | accept | Dedalus | ||
| Sep 5, 2011 at 10:38 | comment | added | Torsten Ekedahl | I would use "free product with amalgamation" only when the upper corner group injects into the other two groups. This is also the case when you have a really nice description of the result. Otherwise you only get a presentation (given presentation for the three groups) and we all know how difficult such can be to handle... | |
| Sep 5, 2011 at 10:26 | answer | added | Tim Porter | timeline score: 6 | |
| Sep 5, 2011 at 7:01 | answer | added | ACL | timeline score: 5 | |
| Sep 3, 2011 at 22:28 | comment | added | Dylan Wilson | I think Ryan is saying that the "free product with amalgamation" interpretation of a pushout of groups is just a general categorical fact: in any category with finite coproducts and coequalizers, the pushout of $A \rightarrow B$ along $A \rightarrow C$ is the coequalizer the two maps into the coproduct of $B$ and $C$. | |
| Sep 3, 2011 at 22:13 | comment | added | Ryan Budney | "push-out" and "free product with amalgamation" are pretty much synonymous, so it's not clear to me there's anything happening to generalize. | |
| Sep 3, 2011 at 22:04 | history | asked | Dedalus | CC BY-SA 3.0 |