Timeline for Position of indices in QFT
Current License: CC BY-SA 3.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jul 8, 2016 at 22:00 | answer | added | gented | timeline score: 2 | |
| Jul 8, 2016 at 21:34 | comment | added | blackhole1511 | Okay, I can understand that, then I should take into account that the index position actually matters in these situations, right? Thank you! | |
| Jul 8, 2016 at 21:24 | comment | added | knzhou | As a simpler case, if you wanted $A^0$ and Schwartz wrote $A^\mu = B_\mu$, you would have to raise the index to $B^\mu$ first, then extract $B^0$. | |
| Jul 8, 2016 at 21:23 | comment | added | knzhou | @blackhole1511 You need to figure out where the indices go before plugging in specific components. It'll take some extra work, but you can always recover the positioning uniquely. | |
| Jul 8, 2016 at 21:10 | comment | added | blackhole1511 | I still don't understand what that means... for example, if I want to compute $T_{11}$, I would get $T_{11}=\sum_n \frac{\partial L}{\partial(\partial_x \phi_n)}\partial_x \phi_n +L$. Now I could do the same for the other definition and I get $T_{11}=\sum_n -\frac{\partial L}{\partial(\partial_x \phi_n)}\partial_x \phi_n +L$ . How are they the same? | |
| Jul 8, 2016 at 20:44 | comment | added | knzhou | It's not a typo. In Schwartz, $F^{\mu\nu} = F_{\mu\nu} = F_{\mu}^{\ \nu}$, and so on. | |
| Jul 8, 2016 at 20:39 | comment | added | Jahan Claes | The first author is being careless with indices. | |
| Jul 8, 2016 at 20:28 | history | asked | blackhole1511 | CC BY-SA 3.0 |