All Questions
Tagged with conservation-laws symmetry
302
questions
2
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3
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192
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Two contradictory derivations of Killing equation
In David Tongs lecture notes he derives the Killing equation by showing that the charge $Q=\xi_\mu \frac{\mathrm{d}x^\mu}{\mathrm{d}\tau}$ is conserved
$$ 0=\frac{\mathrm{d}Q}{\mathrm{d}\tau}=\frac{\...
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1
answer
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Designing a thought experiment on Noether's Theorem [closed]
By Noether's theorem, in classical physics, conservation of total momentum of a system is result of invariance of physical evolution by translation.
So logic says "if" there exists closed ...
- 1,409
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Does Noether's theorem apply to a strict on-shell symmetry of the action that holds on every integration region?
I've worked through different proofs of Noether's theorem and read various posts about it on this site. Some important takeaways, among others from this and this post by Qmechanic were
Every off-...
- 587
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1
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Symmetry transformation exact meaning
In whatever text/review I happen to come across (like for example From Noether’s Theorem to Bremsstrahlung: A pedagogical introduction to
Large gauge transformations and Classical soft theorems, ...
- 3,992
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1
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49
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Finding the Noether current
I'm currently reading "QFT for the gifted Amateur by Lancaster and Blundell, and in a lot of the problems I'm a bit unsure of how to do them, an example asked
"Consider a system ...
1
vote
1
answer
96
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How is Noether’s theorem actually applied?
Noether’s theorem roughly states that the existence of a symmetry group for a given system implies a conservation law for that system. All well and good, except that I’m shaky on exactly how you ...
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31
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Noether's theorem for supersymmetry [duplicate]
I know that Noether's theorem states that all symmetries of the universe correspond to some conservation law. If supersymmetry were true, would there be a new conservation law? In other words, does ...
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4
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Why exactly does time translation symmetry lead to conservation of energy? [duplicate]
As far as I know (and I don't know much), Noether's theorem claims that time translation invariance of the laws of physics leads to the conservation of energy. The way I understand it is that if we ...
3
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5
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What is the point of knowing symmetries, conservation quantities of a system?
I think this kind of question has been asked, but i couldn’t find it.
Well i have already know things like symmetries, conserved quantities and Noether’s theorem, as well as their role in particle ...
- 311
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1
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Discrepance between gauge symmetry and Noether's first theorem
In QFT we're interested in the symmetries of our theory (encoded in the invariance of the Lagrangian under symmetries) because they let us study conserved currents of the theory by Noether's theorem.
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- 309
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Conserved current transforming under adjoint
If we have a Lagrangian with a global internal symmetry $G$. Why do the conserved currents transform under the adjoint representation of $G$? Is it a general statement (if this is the case, how can we ...
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22
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Have all the symmetries of the standard model of particle physics been found?
Background
The standard model of particle physics is entirely determined by writing down its Lagrangian or, equivalently, writing down the corresponding system of PDEs.
Every set of PDEs has a ...
- 323
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Charge conservation and $U(1)$-invariance [duplicate]
Let’s consider electromagnetic Lagrangian
$$\mathcal L=-{1\over 4}F_{\mu\nu}F^{\mu\nu}\tag{1}$$
Is charge conservation derived as a consequence of $U(1)$-invariance of this Lagrangian?
user394668
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Deriving conserved currents from variation of action
I am reading An Modern Introduction to Quantum Field Theory by Maggiore. I have difficulty following the calculation of $\delta ( d^4 x)$ and $\delta (\partial_\mu \phi_i)$. Also, wonder whether the ...
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Which Potentials lead to Kepler's second Law?
Which type of potentials lead to Kepler's second law "same area in same time"?
$$dA=\frac{1}{2} \vec{r} \times \vec{dr}.$$
$$\frac{dA}{dt}=c=\vec{r} \times \frac{\vec{dr}}{dt}=\vec{r} \...
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