Spherical Harmonics/Angular Momentum

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SUMMARY

The discussion centers on the relationship between the angular momentum operators in quantum mechanics, specifically the raising operator \( \hat{L}_+ \) and the operator \( L_z \). The participant attempts to demonstrate that \( L_+ = (x + iy)^m \) by relating it to the eigenstates \( |lm\rangle \) and the action of \( L_z \) on these states. The conclusion emphasizes the importance of maintaining the distinction between kets and their representations, as misrepresenting \( (x + iy)^m \) as \( |lm\rangle \) is a significant error in notation.

PREREQUISITES
  • Understanding of quantum mechanics, specifically angular momentum operators
  • Familiarity with the notation and properties of kets and bras in quantum mechanics
  • Knowledge of the mathematical representation of complex numbers in quantum states
  • Basic grasp of operator algebra in quantum mechanics
NEXT STEPS
  • Study the properties of angular momentum operators in quantum mechanics
  • Learn about the action of raising and lowering operators on quantum states
  • Explore the mathematical representation of kets and their corresponding bases
  • Investigate the implications of operator notation and its correct usage in quantum mechanics
USEFUL FOR

Students and professionals in quantum mechanics, particularly those studying angular momentum and operator theory, will benefit from this discussion.

atomicpedals
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Homework Statement



Given that Lz(x+iy)m=m\hbar(x+iy)m. Show that L+=(x+iy)m.

2. The attempt at a solution

I'm probably grasping at straws here, but when I see the expression for Lz I instantly go to Lz|lm>=m\hbar|lm>. This then leads me to suspect that |lm>=(x+iy)m. Is this correct, and how on Earth does it get me any closer to what I want to show for the raising operator?
 
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Not exactly. What \hat{L}_z(x+iy)^m=\hbar m(x+iy)^m tells you is that (x+iy)^m \propto \langle x,y | l~m \rangle. You need to keep the distinction between kets and the representation of the ket in some basis. Writing (x+iy)^m = |l~m\rangle is, at best, a terrible abuse of notation.

I have no idea what \hat{L}_+ = (x+iy)^m is supposed to mean.
 

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