Timeline for Why is Noether's theorem important?
Current License: CC BY-SA 4.0
11 events
| when toggle format | what | by | license | comment | |
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| Aug 26, 2019 at 3:30 | history | edited | user1379857 | CC BY-SA 4.0 |
explained why initial conditions aren't conserved quantities
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| Feb 27, 2018 at 21:05 | history | edited | user1379857 | CC BY-SA 3.0 |
changed fermion to lepton and z to xy
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| Feb 26, 2018 at 22:37 | comment | added | user1379857 | For anyone else interested in details, $A$ does not actually need to be $0$ in order for the transformation to be a symmetry, $A$ need only be a total time derivative, say $A = \dot C$. In such a case, $B - C$ would then be the complete conserved quantity. A good example of this is time translations. Under a time translation $q \to q + \varepsilon \dot q$, our "$A$" would be $A = \dot L$, and $B - L$ turns out to be the energy. | |
| Feb 26, 2018 at 22:29 | comment | added | user1379857 | Well, seeing as you can choose the variations $\varepsilon$, you can indeed impose that $\dot \varepsilon$ is small. Furthermore, another (perhaps slightly more rigorous way) to do calculus of variations is to take the variation in the path to be $\varepsilon \eta(t)$, where $\eta$ is not infinitessimal, and $\varepsilon$ is constant. As long as $\dot \eta$ is bounded above, $\varepsilon \dot \eta$ will shrink as $\varepsilon \to 0$. | |
| Feb 26, 2018 at 22:21 | comment | added | anderstood | Why does $\varepsilon$ small imply $\dot\varepsilon$ small? Is it an assumption on $\varepsilon$? | |
| Feb 26, 2018 at 11:14 | vote | accept | Defcon97 | ||
| S Feb 26, 2018 at 10:18 | history | suggested | J. Manuel | CC BY-SA 3.0 |
Added a dot to the q_i variables in the leftmost part of first equation
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| Feb 26, 2018 at 9:58 | review | Suggested edits | |||
| S Feb 26, 2018 at 10:18 | |||||
| Feb 26, 2018 at 6:47 | history | edited | user1379857 | CC BY-SA 3.0 |
added a paragraph answering the question better
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| Feb 26, 2018 at 1:58 | history | edited | user1379857 | CC BY-SA 3.0 |
fixed math typos
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| Feb 26, 2018 at 0:42 | history | answered | user1379857 | CC BY-SA 3.0 |