Timeline for Chromatic number of a graph defined by $n$ lines on the plane
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
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| Feb 16, 2017 at 13:02 | comment | added | Tony Huynh | Nice question. The original problem follows from Grötzsch's Theorem, but that is a bit like killing a mosquito with a cannon. | |
| Feb 15, 2017 at 19:54 | comment | added | Ben Barber | An alternative construction to that given below is to draw a $K_5$ in the conventional fashion then delete two non-adjacent boundary pieces. The inner cycle has a unique $3$-colouring $12123$ up to isomorphism, and then the points of the star are coloured $33312$, with one of the pairs of $3$'s adjacent. This also uses $8$ lines, which makes me wonder if there's a construction that uses fewer. | |
| Feb 15, 2017 at 18:33 | vote | accept | Fedor Petrov | ||
| Feb 15, 2017 at 18:28 | answer | added | Thomas Bloom | timeline score: 12 | |
| Feb 15, 2017 at 16:51 | history | edited | Fedor Petrov | CC BY-SA 3.0 |
added 78 characters in body
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| Feb 15, 2017 at 16:37 | history | edited | Fedor Petrov | CC BY-SA 3.0 |
added 7 characters in body
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| Feb 15, 2017 at 15:59 | history | asked | Fedor Petrov | CC BY-SA 3.0 |