All Questions
Tagged with momentum noethers-theorem
28
questions
-3
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116
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Noether's theorem by a taste of logic [closed]
I am a mathematician and I asked this question briefly and my question became closed, may be - I don't know - because physicists don't used to apply the method of "proof by contradiction". ...
- 1,409
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0
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Poincaré group conservation laws: 10 of 7? [duplicate]
According to the Wikipedia page about the Poincaré group, we get 10 conservation laws using Noethers theorem.
10 generators (in four spacetime dimensions) associated with the Poincaré symmetry, by ...
- 1,440
2
votes
1
answer
141
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Noether momentum for the electromagnetic field in Susskind's Theoretical Minimum
In Susskind's Special Relativity and Classical Field Theory, he derives an expression for the Noether momentum of an electromagnetic field. He defines Noether momentum to be the notion of momentum ...
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1
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In a simple case of a particle in a uniform gravitational field, do we have translation invariance or not?
Consider a system where a particle is placed in a uniform gravitational field $\vec{F} = -mg\,\vec{e}_{z}$. The dynamics of this are clearly invariant under translations. When we take $z\rightarrow z+...
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What does general relativity say about energy-momentum relationship in unstable space-time?
Suppose that there is an isotropic, homogenous space which is non-stationary in time (expanding/collapsing).
Let say that some package of electromagnetic radiation flows in portion of space far from ...
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3
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0
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97
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Is momentum conserved in our current cosmological models? [duplicate]
The cosmological principle states that the universe, on large enough scales, is homogenous and isotropic. Noether's theorem says that space-translational invariance corresponds to conservation of ...
- 8,640
2
votes
1
answer
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Noether's Theorem and conservation of momentum
So as we all know for a system that has translational symmetry Noether's Theorem states that momentum is conserved, more precisely the theorem states that the quantity:
$$\frac{\partial L}{\partial \...
- 4,577
1
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0
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How are momentum and energy conservation implied by the invariance of laws of physics in space and time respectively?
This excellent article introducing me to the Noether's Theorem mentions that the conservation of momentum and energy are implied by the invariance of laws of physics in space and time respectively.
I ...
- 1,421
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2
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137
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Why are certain quantities so fundamental to physics? [closed]
Apart from having a qualitative description of quantities such as momentum, work and energy, why are these quantities considered so fundamental? What is the reason to define them in the first place? ...
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4
votes
2
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694
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Physical significance of the canonical energy-momentum tensor
I have a question regarding the physical significance of the canonical energy momentum tensor $T_\nu ^\mu$ in the context of classical field theory. It is defined as
$T_\nu ^\mu = \frac{\partial \...
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0
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1
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Where do I go from here to show that linear momentum is conserved under all instances of translation symmetry?
I've worked through a simple derivation of symmetries implying conservation laws from an invariant Lagrangian.
Namely a quantity $Q$ is conserved in the equation below, where
$i$ is a degree of ...
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26
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4
answers
2k
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Elementary argument for conservation laws from symmetries *without* using the Lagrangian formalism
It is well known from Noether's Theorem how from continuous symmetries in the Lagrangian one gets a conserved charge which corresponds to linear momentum, angular momentum for translational and ...
- 481
8
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4
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624
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Connection between Noether's Theorem and classical definitions of energy / momentum
In classical mechanics, change in momentum $\Delta \mathbf p$ and change in kinetic energy $\Delta T$ of a particle are defined as follows in terms of the net force acting on the particle $\mathbf F_\...
- 1,826
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Inferring the conservation of angular momentum from linear momentum [duplicate]
Working in 3-dimensions, if we are given a Lagrangian containing $N$ particles. Say, through Noether's theorem, we know that the sum of the linear momentum of all $N$ particles in each direction are ...
user148792
3
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2
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How can linear and angular momentum be different?
The earth orbiting around the sun has an angular momentum. But at one moment of time, each atom on earth is moving translationally, and the combined linear momenta of all the particles on earth would ...
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