Symmetries and conserved quantities

In summary, the conservation of angular momentum is due to the rotational invariance of the Hamiltonian. However, if an elliptically symmetric potential is produced, the particle's momentum along the curve of the ellipse will not be conserved. The only conserved quantity in this case is the angular momentum along the z-axis. Additionally, in the case of an elliptic potential well, the total angular momentum will not be conserved, but the angular momentum around the azimuthal direction will be.
  • #1
plmokn2
35
0
I know that if a particle is in a spherically symetric potential its angular momentum will be conserved, but what about if somehow we manage to produce say an elliptically symmetric potential? Will the particle then have a momentum along the curve of the ellipse conserved?
Thanks
 
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  • #2
It should be, because the conservation of angular momentum is from the
rotational invariance of the Hamiltonian.
 
  • #3
No. Angular momentum is not "momentum along the curve of a circle", but rather [itex]\vec x\times\vec p[/itex]. There is nothing comparable that is conserved for a generic elliptically symmetric potential.
 
  • #4
I think his 'momentum' here is angular momentum.
If your elliptically symmetric potential is [tex]V(\rho,z)=\frac{1}{\rho^2+\alpha z^2},~\alpha\neq 1[/tex], then angular momentum along axis
'z' is conserved.
 
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  • #5
The only thing i can remember know is that in case of an elliptic potential well, J = L + S is not a good quantum number, science the energy eigenvalues will be "mixed" with same M_J etc, c.f The Nilsson model of Atomic Nucleus.
 
  • #6
Thanks for your replies, sorry for the slightly ambiguious question.
 
  • #7
Angular momentum around the azimuthal direction will still be conserved, but the TOTAL angular momentum will not. This is basically what PRB147 said, but maybe slightly clarified.
 

1. What are symmetries and conserved quantities?

Symmetries are properties of a system that remain unchanged when certain transformations are applied to it. Conserved quantities are physical properties that do not change over time, even when the system undergoes transformations.

2. Why are symmetries and conserved quantities important in science?

Symmetries and conserved quantities provide fundamental principles for understanding the behavior of physical systems. They can be used to make predictions and explain the laws of nature.

3. How are symmetries and conserved quantities related?

Symmetries often lead to conserved quantities. For example, the symmetry of translation in space leads to the conservation of momentum, and the symmetry of rotation leads to the conservation of angular momentum.

4. How do symmetries and conserved quantities impact our understanding of the universe?

Symmetries and conserved quantities are essential for understanding the fundamental laws of nature and the behavior of particles and systems at both the macroscopic and microscopic levels. They play a crucial role in theories of physics, such as the theory of relativity and quantum mechanics.

5. Can symmetries and conserved quantities change or be violated?

In some cases, symmetries and conserved quantities can be broken or violated. For example, the symmetry of charge conservation can be violated in certain particle interactions. However, these violations are still consistent with the overall principles of symmetries and conserved quantities.

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