How Do You Solve Bessel Function Integrals?

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Discussion Overview

The discussion revolves around solving an integral involving Bessel functions of the first kind, specifically the integral \(\int_{0}^{R} J_{m-1}(ax) J_{m+1}(ax) x \, dx\), where \(J_{m-1}\) and \(J_{m+1}\) are Bessel functions and \(a\) is a constant. The scope includes theoretical exploration and potential simplification techniques related to Bessel functions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant seeks guidance on solving the integral involving Bessel functions.
  • Another participant suggests that there may be an identity relating successive Bessel functions, which could simplify the integral.
  • A third participant mentions the orthogonality of Bessel functions as a potential area of relevance for the integral.
  • There is a repeated suggestion to explore identities that relate \(J_{m+1}\) to \(J_m\) to aid in simplification.
  • A participant indicates they have solved the integral after considering the suggestions provided.

Areas of Agreement / Disagreement

Participants generally agree on the potential usefulness of identities and orthogonality in simplifying the integral, but there is no consensus on a specific method or identity to apply. The discussion remains open-ended regarding the best approach to solving the integral.

Contextual Notes

Some assumptions about the properties of Bessel functions and their identities are present, but these are not fully explored or resolved in the discussion.

jayryu
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hello,everyone
i want to know how to solve this bessel function integrals:

\int_{0}^{R} J_m-1(ax)*J_m+1 (ax)*x dx
where J_m-1 and J_m+1 is the Bessel function of first kind, and a is a constant.

thanks.
 
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Is this what you meant to post?

\int_{0}^{R} J_{m-1}(ax)*J_{m+1} (ax)*x \ dx

I am not an expert on Bessel functions, but isn't there an identity that you can use to simplify this expression? Something like

J_{m+1} = Some \ function \ of \ J_m

In other words, each successive Bessel function can be defined in terms of its predecessor. For example,

J1 = some function of J0,
J2 = some function of J1,
J3 = some function of J2,
J4 = some function of J3,
etc.

If you can find this identity, you should be able to simplify your integral.
 
Perhaps you will find what you are looking for reading about the orthogonality of the Bessel functions. If you don't already know about that, try looking at:

http://www.hit.ac.il/ac/files/shk_b/Differential.Equations/Orthogonality_of_Bessel_functions.htm
 
Last edited by a moderator:
LCKurtz said:
Perhaps you will find what you are looking for reading about the orthogonality of the Bessel functions. If you don't already know about that, try looking at:

http://www.hit.ac.il/ac/files/shk_b/Differential.Equations/Orthogonality_of_Bessel_functions.htm

thank you,i'll try that!
 
Last edited by a moderator:
DuncanM said:
Is this what you meant to post?

\int_{0}^{R} J_{m-1}(ax)*J_{m+1} (ax)*x \ dx

I am not an expert on Bessel functions, but isn't there an identity that you can use to simplify this expression? Something like

J_{m+1} = Some \ function \ of \ J_m

In other words, each successive Bessel function can be defined in terms of its predecessor. For example,

J1 = some function of J0,
J2 = some function of J1,
J3 = some function of J2,
J4 = some function of J3,
etc.

If you can find this identity, you should be able to simplify your integral.

yes,it is.thanks for your suggestions.i have solved it.:smile:
 

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