Timeline for Is the value of the action important?
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| Jul 10, 2022 at 8:15 | vote | accept | Mauro Giliberti | ||
| Jul 9, 2022 at 17:51 | comment | added | Qmechanic♦ | Coleman's action $S_E$ is relative, i.e. a difference between the absolute action of different instanton sectors. | |
| Jul 9, 2022 at 16:58 | comment | added | Mauro Giliberti | I don't understand at what point exactly in your answer the value of the action becomes important. The fact that the action in Coleman's example is the one of a single instanton shouldn't make a difference, right? A shift of the action of a single instanton shouldn't be physically relevant. Is the normalization choice that's not invariant? Could you highlight, in your answer, why a generic action is shift invariant but Coleman's one isn't? | |
| Jul 9, 2022 at 8:54 | comment | added | Qmechanic♦ | I updated the answer. | |
| Jul 9, 2022 at 8:52 | history | edited | Qmechanic♦ | CC BY-SA 4.0 |
Added explanation
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| Jul 9, 2022 at 0:00 | comment | added | Mauro Giliberti | this changes a lot of what I thought I understood. How is Coleman's Euclidean action different from the action in the path integral? It must be different, since a shift of Coleman's action is relevant, while a shift of the path integral's action isn't. Is it the fact that in the path integral I integrate the action, but I don't integrate the content of Coleman's one? If that's the case, I'd be more inclined to say that it's the integration that's invariant under overall shifts, not the action itself, therefore I suspect this isn't the correct reasoning. | |
| Jul 8, 2022 at 19:23 | history | edited | Qmechanic♦ | CC BY-SA 4.0 |
Added explanation
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| Jul 8, 2022 at 19:23 | comment | added | Qmechanic♦ | An overall shift of the action in the path integral or the statistical partition function is not physical relevant as well. | |
| Jul 8, 2022 at 15:49 | history | edited | Qmechanic♦ | CC BY-SA 4.0 |
Added explanation
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| Jul 8, 2022 at 15:42 | vote | accept | Mauro Giliberti | ||
| Jul 8, 2022 at 23:55 | |||||
| Jul 8, 2022 at 15:40 | comment | added | Mauro Giliberti | So the action is classically used only as a functional to be minimized, and so classical physics is invariant if $S\rightarrow S+5$, while the quantum path integral uses the value of the action to compute probability amplitudes, that therefore are not invariant if $S\rightarrow S+5$? It's the quantumness that seals the deal, not the Euclideaness, right? | |
| Jul 8, 2022 at 15:21 | history | answered | Qmechanic♦ | CC BY-SA 4.0 |