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### What's the commutator of $|\mathbf{\hat{x}}|$ and $|\mathbf{\hat{p}}|$? [closed]

Straight to the point: what's the result of the commutator of the magnitude of the position and the momentum operators and how can I approach it, i.e., $[|\mathbf{\hat{x}}|,|\mathbf{\hat{p}}|]=$ ? My ...
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### Differentiation and delta function

Need help doing this simple differentiation. Consider 4 d Euclidean(or Minkowskian) spacetime. $$\partial_{\mu}\frac{(a-x)_\mu}{(a-x)^4}= ?$$ where $a_\mu$ is a constant ...
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### The magnetic field of a magnetic monopole

Let us define the magnetic field $$\vec{B} = g\frac{\vec{r}}{r^3}$$ for some constant $g$. How can we show that the divergence of this field correspond to the charge distribution of a single magnetic ...
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### Dirac delta function equation intuition and proof [duplicate]

What is the intuition and where should I find proof of this equation (do not know what its name is). It is used to derive Gauss law from Newton equation. {\nabla \cdot \Bigg ( \frac{\vec{s}}{|\vec{s}...