Bessel Functions and Shifted Integral Limits: How Are They Related?

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Discussion Overview

The discussion revolves around the relationship between Bessel functions of the first kind and their definitions when integral limits are shifted. Participants explore whether the expressions with different limits yield the same results and the implications of this on the properties of Bessel functions.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant defines the nth order Bessel function of the first kind and poses a question about the relationship between the standard integral limits and shifted limits.
  • Another participant argues that the two functions are different based on numerical integration results from MathCAD, although they do not provide a formal proof.
  • A later reply asserts that the two functions are equal and references a proof, although the details of this proof are not provided in the discussion.
  • One participant expresses gratitude for the proof and mentions having verified the equality using MathCAD, seeking a citation for the proof provided.
  • Another participant confirms that the proof is their own and states that it does not require citation as the calculus involved is classical.
  • There is a question about the equivalence of different notations for Bessel functions used in MathCAD, indicating some uncertainty about terminology.

Areas of Agreement / Disagreement

Participants express differing views on whether the two expressions are equal. While one participant asserts they are equal, another participant provides numerical evidence suggesting they are not, leading to an unresolved debate.

Contextual Notes

The discussion includes references to numerical methods and personal verification, but lacks formal mathematical proofs or detailed derivations to support the claims made. The implications of the shifted limits on the properties of Bessel functions remain unclear.

Who May Find This Useful

This discussion may be of interest to those studying Bessel functions, numerical integration techniques, or exploring the properties of mathematical functions in applied contexts.

dfrenette
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A nth order bessel function of the first kind is defined as:

Jn(B)=(1/2pi)*integral(exp(jBsin(x)-jnx))dx

where the integral limits are -pi to pi

I have an expression that is the exact same as above, but the limits are shifted by 90 degrees; from -pi/2 to 3pi/2

My question is how does this new expression relate to Bessel functions? My first thought was that the two function are equal since the integral limits are over one period. But I am not sure.
 
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I think they are different. I can not offer a mathematical proof, but using MathCAD function for Jn and its numerical integration, I obtained different numbers.
 
My question is how does this new expression relate to Bessel functions? My first thought was that the two function are equal since the integral limits are over one period. But I am not sure.
You are right. The two functions are equal.
A more tedious proof is given in the joint page :
 

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Super,
Thanks for the proof!

I did set up a little mathcad file (attached) that shows the two implementations, proving to myself that indeed they are equal, but this proof will come in handy.

Where did you get it from so I can cite it?

Thanks again,

Darren
 

Attachments

JJacquelin said:
You are right. The two functions are equal.
A more tedious proof is given in the joint page :
Nice proof. I stand corrected.

The Bessel function I tried in MathCAD is: Jn(m, x) which returns Jm(x). Is this the same thing?
 
Where did you get it from so I can cite it?
It's written by myself. You can copy it. No need to cite an author : the calculus is rather classical.
 
Perfect. Thanks again.
 

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