Timeline for Why is the Yang-Mills gauge group assumed compact and semi-simple?
Current License: CC BY-SA 3.0
9 events
| when toggle format | what | by | license | comment | |
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| Feb 9, 2021 at 18:21 | answer | added | Fermin | timeline score: 2 | |
| May 19, 2019 at 10:24 | history | edited | Qmechanic♦ |
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| Sep 18, 2013 at 9:30 | answer | added | Stan | timeline score: 14 | |
| Feb 6, 2013 at 7:57 | vote | accept | joshphysics | ||
| Jan 29, 2013 at 16:03 | history | tweeted | twitter.com/#!/StackPhysics/status/296287528250638337 | ||
| Jan 29, 2013 at 15:02 | answer | added | Qmechanic♦ | timeline score: 25 | |
| Jan 29, 2013 at 8:15 | answer | added | twistor59 | timeline score: 12 | |
| Jan 29, 2013 at 7:34 | comment | added | Luboš Motl | Compactness is needed for the bilinear form on the adjoint representation to be positively definite. For example, $SO(2,1)$ would be no good because the signature on the adjoint is ${+}{-}{-}$. If we had an indefinite form, the norm of the different colorful polarizations of the gauge bosons would have different signs (ghosts, negative probabilities). In a similar way, some Lie algebras (not semisimple etc.) have "zero norm" directions. Ultimately, we decompose the gauge group to simple compact pieces - the factors behave independently and decouple. | |
| Jan 29, 2013 at 6:00 | history | asked | joshphysics | CC BY-SA 3.0 |