What Is the Solution to Associated Legendre Polynomials for m=1 and l=1?

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Discussion Overview

The discussion revolves around the solution to the associated Legendre polynomials for the case where m=1 and l=1. Participants explore the mathematical derivation and application of the associated Legendre polynomial formula, particularly in relation to trigonometric functions.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant seeks assistance in deriving the solution for the associated Legendre polynomial when m=1 and l=1, expressing confusion over the calculations.
  • Another participant challenges the initial poster to clarify their understanding and reasoning behind their attempts, suggesting they should be able to perform the calculation themselves.
  • A participant who is not a physics/math student shares their derived expression, indicating a misunderstanding of the relationship between their result and the expected solution involving sin(θ).
  • One participant points out a potential error in the calculations of the previous poster and provides a formula for the associated Legendre polynomial, suggesting a simplification process.
  • The original poster later acknowledges their earlier mistakes and confirms they have arrived at the correct expression for sin(θ) after considering the feedback received.

Areas of Agreement / Disagreement

The discussion includes both confusion and clarification, with some participants correcting earlier claims and others expressing uncertainty. There is no clear consensus on the initial understanding, but later contributions lead to a resolution for the original poster.

Contextual Notes

Participants express varying levels of familiarity with the topic, and there are indications of missing foundational knowledge that affect the clarity of the discussion.

bvol
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9def74632e12c73e7638541a31d51fca.png


m=1 and l=1

x = cos(θ)

What would be the solution to this?

Thanks.
 
Last edited:
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We won't do the calculation for you. Why can't you do it yourself? What part of it doesn't make sense to you?
 
I've tried a lot of things, but I don't get it. (NOT a physics/math student)

I get this:

4cos(θ)^3 - 4cos(θ)

But it should be sin(θ) since I'm applying this formula:

40d6f1331ce8aba3f36bc39d3a8fae78.png


and the solution for 1,1 is Sqrt(3/8π) e^((+/-)iφ) * sin(θ)
I get how the part in italics is derived, but not how the part in bold has been derived from the associated legendre polynomial..
 
I think you've made an error in your calculation. If we plug in ##\ell = 1## and ##m=1##, we have $$P^{1}_{1}={(-1)^1 \over 2 \cdot 1!} (1-x^2)^{1/2} \cdot {d^2 \over dx^2}(x^2-1)$$
Do you have that much? It should be easy to simplify that, then plug in ## x=\cos{\theta}##.
 
Great I have it now. -(1-cos()^2)^(1/2), which is equal to sin(θ).

Right I have it now, like you said I made a small error in not applying l+m, but instead just l and some errors on other places as well.

Thanks for the quick reply! :)
 

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