Expansion in spherical harmonics sin(theta)

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SUMMARY

The discussion focuses on expanding the function sin(theta) in terms of spherical harmonics, specifically addressing the expression (3cos^2(theta+45°)-1)*exp(i*(psi+45°). The user encounters issues with obtaining zero coefficients when applying the integrals from Wikipedia for spherical harmonics. It is established that the coefficients are not all zero, with the first coefficient being proportional to f_{0}^0 α ∫^{2π}_{0}dφ ∫^{π}_{0}dθ sin²(θ) = π², indicating a potential misunderstanding of the expansion process along arbitrary axes.

PREREQUISITES
  • Understanding of spherical harmonics and their mathematical properties
  • Familiarity with integral calculus, particularly double integrals
  • Knowledge of complex exponentials and their applications in physics
  • Basic trigonometric identities and transformations
NEXT STEPS
  • Study the derivation and properties of spherical harmonics in detail
  • Learn about the application of spherical harmonics in quantum mechanics
  • Explore the method of expanding functions in terms of orthogonal functions
  • Investigate the implications of expanding functions along arbitrary axes
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This discussion is beneficial for physics students, mathematicians, and researchers working with spherical harmonics, particularly in fields such as quantum mechanics and mathematical physics.

Gerenuk
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Homework Statement



I want to expand sin(theta) in spherical harmonics.
Well, actually I want
(3cos^2(theta+45°)-1)*exp(i*(psi+45°))
but I think I could find my mistake by the above simple example.

Homework Equations



http://en.wikipedia.org/wiki/Spherical_harmonics

The Attempt at a Solution



I seem to get zero for all coefficients by the integrals from wikipedia.
Can I not expand along an arbitrary axis?
 
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The coefficients are not all zero. For instance, the first coefficient is proportional to:

f_{0}^0 \alpha \int^{2\pi}_{0}d\phi\int^{\pi}_{0}d\theta sin^{2}(\theta)=\pi^2
 

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