Timeline for When is the category of models of a limit theory a topos?
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
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| S Sep 21, 2018 at 12:17 | history | suggested | Ivan Di Liberti |
added a new tag
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| Sep 21, 2018 at 9:45 | review | Suggested edits | |||
| S Sep 21, 2018 at 12:17 | |||||
| Sep 21, 2018 at 8:38 | vote | accept | Jonathan Gallagher | ||
| Sep 20, 2018 at 7:52 | comment | added | Simon Henry | Thanks ! I knew about the example of Jonsson-Tarski algebras but I wasn't aware of such a characterization. | |
| Sep 20, 2018 at 1:38 | comment | added | Jonathan Gallagher | @TomLeinster. Yes, that is correct the reference I was referring to. A link I have is link.springer.com/content/pdf/10.1007/BF01188056.pdf but I don't know if it's available without subscription. | |
| Sep 19, 2018 at 17:13 | comment | added | Tom Leinster | @SimonHenry I imagine Jonathan is referring to Johnstone's paper "When is a variety a topos?", Algebra Universalis 21 (1985), 198-212. An interesting point made in that paper is that alongside the obvious family of examples of finite product theories whose models form a topos (namely, M-sets for a monoid M), there's a not-so-obvious family: the so-called Jónsson-Tarski algebras and generalizations thereof. A JT algebra is a set $A$ equipped with a bijection $A \to A \times A$. | |
| Sep 19, 2018 at 8:18 | comment | added | Simon Henry | I don't know this result of Johnstone you are refering to, could you provide a more precise reference ? that sound interesting. | |
| Sep 19, 2018 at 7:15 | answer | added | Ivan Di Liberti | timeline score: 15 | |
| Sep 19, 2018 at 1:24 | history | asked | Jonathan Gallagher | CC BY-SA 4.0 |