What is the result of J_x, J_y, and [J_x,J_y] acting on a specific eigenstate?

In summary, the simultaneous eigenstate of \mathbf{J}^2 and J_z with eigenvalues 0 and 0, |0,0\rangle, cannot be operated on by J_x and J_y since the m eigenvalue must remain at 0 in a j=0 state. This results in a normalization constant of 0 for all operations, leading to unsatisfactory results.
  • #1
jfy4
649
3

Homework Statement


Let [itex]|0,0\rangle [/itex] be the simultaneous eigenstate of [itex]\mathbf{J}^2[/itex] and [itex]J_z[/itex] with eigenvalues 0 and 0. Find
[tex]
J_x|0,0\rangle \quad\quad J_y |0,0\rangle \quad\quad [J_x,J_y]|0,0\rangle
[/tex]

2. The attempt at a solution
It seemed reasonable to write [itex]J_x[/itex] and [itex]J_y[/itex] in terms of ladder operators
[tex]
J_{+}=J_x + iJ_y
[/tex]
[tex]
J_{-}=J_x -i J_y
[/tex]
and then to have them operate on the states (for the last one I would just use the x,y,z commutation relations). But I was looking at the normalization constant out front
[tex]
J_{+}|j,m\rangle = \hbar\sqrt{(j+m+1)(j-m)} |j,m+1\rangle
[/tex]
[tex]
J_{-}|j,m\rangle = \hbar \sqrt{(j-m+1)(j+m)}|j,m-1\rangle
[/tex]
but given the initial state, these seem to be zero... Please tell me I'm doing this wrong, zero is such a unsatisfactory answer...

Thanks,
 
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  • #2
Because you are in a j=0 state, you can't actually raise or lower the m eigenvalue since m ranges between -j and +j so in this case it must stay 0.

So, it would seem like indeed you get 0 for everything.
 

1. What is an Angular Momentum Eigenstate?

An Angular Momentum Eigenstate is a quantum state that describes the angular momentum of a particle. It is a state in which the angular momentum of the particle has a definite value and direction.

2. How is Angular Momentum Eigenstate related to Angular Momentum?

Angular Momentum Eigenstates are related to Angular Momentum through the principle of superposition. The total angular momentum of a particle can be described as a linear combination of its eigenstates.

3. Can Angular Momentum Eigenstates exist for all types of particles?

Yes, Angular Momentum Eigenstates can exist for all types of particles, as long as they have angular momentum. This includes particles such as electrons, protons, and neutrons.

4. How do Angular Momentum Eigenstates behave under rotations?

Angular Momentum Eigenstates behave differently under rotations compared to other quantum states. They maintain their eigenstate properties and only change in phase.

5. How are Angular Momentum Eigenstates measured in experiments?

Angular Momentum Eigenstates can be measured through experiments involving angular momentum measurements, such as the Stern-Gerlach experiment. By measuring the angular momentum of a particle in different directions, the eigenstate can be determined.

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