Can a Hamiltonian with non-spherical potential commute with l^2?

In summary, the Hamiltonian of a system with central potential always commutes with the l^2 operator, but this is not the case for non-rotation invariant Hamiltonians. However, it has been shown that the l^2 and x^2 operators do commute even for a non-rotation invariant potential such as a harmonic oscillator potential in the x-direction.
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Feelingfine
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I know that in the case of central potential V(r) the hamiltonian of the system always commutes with l^2 operator. But what happends in this case?
 
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The Hamiltonian ##H=L_z## commutes with ##L^2## but is not rotation invariant. Adding a multiple of ##H=L_z## to a rotation invariant ##H## gives other counterexamples.
 
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  • #3
It's shown here that ##\hat{L}^2## and ##\hat{x}^2## commute

https://physics.stackexchange.com/questions/93533/commutator-of-l2-and-x2-p2

So put a particle in three dimensions to a field described by a harmonic oscillator potential, but only in the x-direction

##V(x,y,z) = ax^2##

That's not rotation invariant, but still commutes with the ##\hat{L}^2## (and hence the whole ##\hat{H}## commutes with ##\hat{L}^2##).
 
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FAQ: Can a Hamiltonian with non-spherical potential commute with l^2?

Can a Hamiltonian with non-spherical potential commute with l^2?

Yes, a Hamiltonian with non-spherical potential can commute with l^2. This is because the commutation between the Hamiltonian and l^2 is determined by the symmetry of the potential. If the potential has spherical symmetry, then it will commute with l^2. However, if the potential does not have spherical symmetry, then it may not commute with l^2.

What is the significance of a non-spherical potential in a Hamiltonian?

A non-spherical potential in a Hamiltonian can represent a more realistic and complex system. It allows for the consideration of different types of interactions and forces, such as anisotropic interactions or external fields. This can lead to a more accurate description of physical systems.

How does the shape of the potential affect the commutation with l^2?

The shape of the potential directly affects the commutation with l^2. If the potential has spherical symmetry, then it will commute with l^2. However, if the potential does not have spherical symmetry, then it may not commute with l^2. This is because the commutation is determined by the symmetry of the potential.

Are there any limitations to a non-spherical potential in a Hamiltonian?

One limitation of a non-spherical potential in a Hamiltonian is that it can be more mathematically complex and difficult to solve compared to a spherical potential. This can make it challenging to obtain analytical solutions and may require numerical methods. Additionally, the physical interpretation of the potential may also be more complex.

How does the commutation with l^2 affect the energy levels of a system?

The commutation with l^2 affects the energy levels of a system by determining the allowed quantum numbers and corresponding energy levels. If the Hamiltonian commutes with l^2, then the energy levels will be quantized and the system will have discrete energy states. If the Hamiltonian does not commute with l^2, then the energy levels may not be quantized, leading to a continuous spectrum of energy states.

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