# Tag Info

Accepted

### Intuition behind the differential equation for forced oscillations

It's better to write the differential equation for forced oscillations in a different way that makes it more relatable to Newton's second law: $$m\ddot{x}=F_0\sin{(\omega''t)}-b\dot{x}-kx$$ Now we can ...
Accepted

### Why is Dirac's Phase Operator Non-Hermitian?

Yeah, that's a strange thing to say - indeed $an^{-1}a^\dagger$ is defined everywhere and equal to the identity (note that $n^{-1}$ itself is not defined everywhere - but it is defined on the image of ...

### Why is Dirac's Phase Operator Non-Hermitian?

I'd do it the other way round: $$(e^{i\phi})^\dagger e^{i\phi}$$ should also be the identity, but $$(e^{i\phi})^\dagger e^{i\phi}= n^{-1/2} a^\dagger a n^{-1/2}$$ is not defined on $|0\rangle$ as ...
We have in fact to check whether for $U:=\exp i\hat \phi$ it holds that $$UU^\dagger = \mathbb I = U^\dagger U \quad .$$ In Phase and Angle Variables in Quantum Mechanics (where in section 5 it is ...