Let $V := \operatorname{span}{(J_1, J_2, J_3)}$ be a Lie algebra over the complex numbers such that
- $J_1$, $J_2$, and $J_3$ are essentially self-adjoint operators on some Hilbert space $\mathcal{H}$.
- The Lie bracket is given by the commutator.
- We have that $[J_i, J_j] = \mathrm{i}\epsilon_{ijk}J_k$.
Let $J^2 := \sum_i J_i \circ J_i$. Then is it true that
- $J_i$'s have a pure point spectrum.
- The common eigenvectors of $J^2$ and $J_3$ come as families $\psi_{j(j+1), m}$, where $m = -j, -j+1, \ldots, j-1, +j$. The eigenvalue $j(j+1)$ is associated to $J^2$ and $m$ is associated to $J_3$ with $j \in \mathbb{N}_0/2$.
I ask this question here as the above conclusions hold for finite dimensional Hilbert spaces, where all linear operators are bounded. We find the above analysis done in almost all introductory QM textbooks, for spin operators, using ladder operators. I want to ask if we can do the same analysis for orbital angular momentum operators.