Angular momentum theory problem probably wrong sign

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SUMMARY

The discussion centers on proving the equality \(\left\langle lm | \vec{\hat{r}} \times \vec{\hat{p}} | lm\right \rangle = \left\langle lm | \vec{\hat{p}} \times \vec{\hat{r}} | lm \right \rangle\), where \(| lm \rangle\) are eigenkets of the angular momentum operator \(\hat{L}^2\). The user attempts to express the angular momentum operator in terms of its components \(\hat{L_x}\), \(\hat{L_y}\), and \(\hat{L_z}\), noting that only the \(\hat{k}\) component survives due to orthogonality. The user suspects a sign error in the problem statement, which complicates the proof. The consensus is that the sign issue is indeed likely the root of the problem.

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  • Understanding of angular momentum operators, specifically \(\hat{L}^2\)
  • Familiarity with bra-ket notation in quantum mechanics
  • Knowledge of vector cross products in quantum mechanics
  • Experience with ladder operators and their application to eigenstates
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  • Review the properties of angular momentum operators in quantum mechanics
  • Study the implications of orthogonality in quantum eigenstates
  • Learn about the use of ladder operators in manipulating quantum states
  • Examine examples of vector cross products in quantum mechanics
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Quantum mechanics students, physicists working with angular momentum, and anyone involved in theoretical physics discussions regarding operator algebra.

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I have to prove that [itex]\left\langle lm | \vec{\hat{r}} \times \vec{\hat{p}} | lm\right \rangle = \left\langle lm | \vec{\hat{p}} \times \vec{\hat{r}} | lm \right \rangle[/itex], where [itex]| lm \rangle[/itex] are eigenkets of angular momentum operator [itex]\hat{L}^2[/itex]

And I can't figure out a way to do this correctly. I wrote the angular momentum operator-vector in terms of its components, [itex]\hat{L_x}[/itex], [itex]\hat{L_y}[/itex] and [itex]\hat{L_z}[/itex], and only the [itex]\hat{k}[/itex] component survives the bra-ket operation, because I can write [itex]\vec{L_x}[/itex] y [itex]\vec{L_y}[/itex] in terms of ladder operators, and after lowering and rising the eigenstates, the corresponding eigenkets (except for the [itex]\hat{k}[/itex] component) cancel with [itex]\langle lm |[/itex] because of the orthogonality property of these eigenkets. Probably there is a wrong sign in the problem statement. Looks trivial in that case, but I want to know your opinion.

Thanks in advance for any advice.
 
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Undoubtedly the wrong sign.
 

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