Derive the orthonormality condition for Legendre polynomials

  • Context: Undergrad 
  • Thread starter Thread starter hmparticle9
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Discussion Overview

The discussion revolves around deriving the orthonormality condition for Legendre polynomials, focusing on integration techniques, particularly integration by parts. Participants explore various approaches and definitions related to Legendre polynomials, their properties, and the implications of their orthogonality.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Some participants express discomfort with applying integration by parts and seek guidance on how to approach the integral involving Legendre polynomials.
  • Others propose using specific definitions of Legendre polynomials and suggest that integration by parts is necessary for the derivation.
  • A few participants discuss the implications of assuming relationships between the indices of the polynomials, such as ##m < l## or ##m \geq n##, and how these affect the integration process.
  • There are mentions of the need to verify boundary conditions and the behavior of monomials in the expansion of ##(x^2-1)^m## when differentiating.
  • Some participants suggest that the proof for the normalization condition of Legendre polynomials follows a similar reasoning to the orthogonality proof, involving integration by parts and handling constants carefully.
  • Concerns are raised about the correctness of certain steps in the derivation, particularly regarding the treatment of derivatives and the resulting integrals.

Areas of Agreement / Disagreement

Participants generally agree that integration by parts is a crucial technique for deriving the orthonormality condition, but there is no consensus on the specific steps or assumptions that should be made during the process. Multiple competing views and approaches remain, with some participants advocating for different definitions and methods.

Contextual Notes

Limitations include unresolved mathematical steps and dependencies on specific definitions of Legendre polynomials. The discussion reflects varying levels of comfort with integration techniques and the handling of boundary conditions.

  • #31
I see :) I was just keeping the leading term. When I think about it I was being a bit reckless. I appreciate your initial solution, very nice. Thank you for your help!
 

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