Coefficients of a Fourier-Bessel series

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Discussion Overview

The discussion revolves around the coefficients of a Fourier-Bessel series, specifically focusing on the orthogonality relations of Bessel functions and the evaluation of integrals involving these functions. The scope includes theoretical aspects and mathematical reasoning related to Bessel functions.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant states the orthogonality relation for Bessel functions and seeks clarification on deriving the second integral result involving the square of Bessel functions.
  • Another participant suggests that a paper may provide insights into the evaluation of the integral related to Bessel functions.
  • A third participant references a specific integral result involving Bessel functions and asks for a general formula for Bessel functions of different orders.
  • One participant proposes using integration by parts and certain relations of Bessel functions to tackle the integral evaluation.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the methods for evaluating the integrals, and multiple approaches and references are suggested without agreement on a definitive solution.

Contextual Notes

Some assumptions regarding the properties of Bessel functions and the specific conditions under which the integrals are evaluated may be implicit in the discussion.

ebernardes
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When finding the coefficients of a Fourier-Bessel series, the Bessel functions satisfies, for [itex]k_1[/itex]and [itex]k_2[/itex] both zeroes of [itex]J_n(t)[/itex], the orthogonality relation given by:
$$\int_0^1 J_n(k_1r)J_n(k_2r)rdr = 0, (k_1≠k_2)$$
and for [itex]k_1 = k_2 = k[/itex]:

$$\int_0^1 J_n^2(kr)rdr = \frac12J_n^{'2}(k)$$

I understand how to get the first result since the Bessel's equation can be interpreted as a Sturm-Liouville problem, but how can I show the second one?
 
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This paper might offer a clue:
 

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SteamKing said:
This paper might offer a clue:

But how exactly i can evaluate the integral and get the result given by: [tex]I = \frac{R^2}{\alpha_m^2 - \alpha_n^2}[\alpha_mJ_0(\alpha_n)J_1(\alpha_m) - \alpha_nJ_0(\alpha_m)J_1(\alpha_n)][/tex] or another more general formula for Bessel functions of different order?
 
I believe an integration by parts is called for, using certain relations of Bessel functions to get over the tricky bits:

http://home.comcast.net/~rmorelli146/U3150/Bessel.pdf
 
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