Timeline for "in" and "out" states in Weinberg's QFT
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Nov 12, 2020 at 5:45 | history | bounty ended | Jiahao Fan | ||
| Nov 4, 2020 at 12:41 | comment | added | mike stone | The state vector $|\Psi\rangle$ is usually not a function of position $x$. The "in" state vector is a function $|{\bf k}_1,{\bf k}_2,\ldots, {\bf k}_N\rangle$ of the the momenta ${\bf k}_i$ of the asymptotically far-separated incoming particles. More precisely one makes wavepackets out of the plane-wave $|{\bf k}_1,{\bf k}_2,\ldots, {\bf k}_N\rangle$ so the that the particles are well separated in the distant past. Those packets can depend on where the particles were long ago but the plane wave states are the ones that used for Lorantz invariance arguments. | |
| Nov 4, 2020 at 12:09 | comment | added | Jiahao Fan | @mikestone Well $\Psi(x)$ is the state vector here so that it does not change with time... | |
| Nov 4, 2020 at 12:02 | comment | added | mike stone | Because in relativistic field theory it is more convenient to make the operators $\psi(x,t)$ time dependent, so that $t$ is on the same footing as $x$.. | |
| Oct 14, 2020 at 5:14 | comment | added | Jiahao Fan | Thanks for your answer! But why does he use Heisenberg picture in the first place? Why not just use Schodinger picture, which explicitly tells the time evolution? | |
| Oct 14, 2020 at 4:00 | history | answered | d_b | CC BY-SA 4.0 |