Can You Solve This Bessel Function Equation Analytically?

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Discussion Overview

The discussion revolves around the analytical solution of a Bessel function equation involving the first order Bessel function, J_{1}. Participants explore the possibility of finding exact or approximate solutions, as well as methods to simplify expressions derived from the equation.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Viet presents the equation (a+b)*J_{1}[x(a+b)]-(a-b)*J_{1}[x(a-b)]=c and inquires about the possibility of an analytical solution.
  • Some participants express skepticism about the feasibility of finding an analytical solution, suggesting that an approximate solution may be more realistic.
  • There is a discussion about the conditions under which analytical approximate solutions can be derived, particularly emphasizing the importance of knowing the parameter ranges.
  • One participant mentions using the Multiplication theorem for Bessel functions but encounters difficulties simplifying the expression (b-1)^n-(b+1)^n.
  • Another participant seeks to simplify (b-1)^n-(b+1)^n using series expansion and asks for alternative series that could facilitate this simplification.
  • There is a clarification regarding the form of the expression (b-1)^n-(b+1)^n and its relation to a function f that depends on b, with examples provided to illustrate the approach.
  • A later reply indicates that simplification may only be possible for n<3, while for n>2, the relationship becomes more complex and dependent on both b and n.

Areas of Agreement / Disagreement

Participants express differing views on the possibility of finding analytical solutions, with some leaning towards approximate methods. The discussion remains unresolved regarding the simplification of the expression and the conditions under which solutions can be derived.

Contextual Notes

Participants note that the ability to derive analytical solutions may depend on the specific values of parameters a and b, and the discussion includes unresolved mathematical steps related to series expansions.

vvthuy
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Hi,

I need to solve one problem like this:

(a+b)*J_{1}[x(a+b)]-(a-b)*J_{1}[x(a-b)]=c

J_{1} denotes the first order Bessel function. Do you think that it is possible to solve this function in an analytical way?

Thanks,

Viet.
 
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vvthuy said:
Hi,

I need to solve one problem like this:

(a+b)*J_{1}[x(a+b)]-(a-b)*J_{1}[x(a-b)]=c

J_{1} denotes the first order Bessel function. Do you think that it is possible to solve this function in an analytical way?

Thanks,

Viet.

Unfortunately not, I think.
 
Thanks for your reply. An approximate solution is also expected.
 
I found an way to modify the above bessel function using Multiplication theorem but I was stuck again at the following step
(b-1)^n-(b+1)^n

Do you know whether I can simplify this using series?
 
vvthuy said:
Thanks for your reply. An approximate solution is also expected.

Generally, analytical approximate solutions are formulas which depend on the range of the parameters values. If nothing is known about the range of the numerical values of the parameters (a, b), probably it is impossible to say if such a formula can be derived.
 
vvthuy said:
I found an way to modify the above bessel function using Multiplication theorem but I was stuck again at the following step
(b-1)^n-(b+1)^n

Do you know whether I can simplify this using series?

The finite series development is :
 

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Thank JJacquelin's comments and the equation. Do you know any other series which allow us to simplify (b-1)^n-(b+1)^n to the form of ()^n?
 
vvthuy said:
Thank JJacquelin's comments and the equation. Do you know any other series which allow us to simplify (b-1)^n-(b+1)^n to the form of ()^n?

What do you mean (?)^n ?
I cannot understand your question.
 
I meant, I tried to get the following form by expansion the left hand side of equation and then combine terms to get the right hand side

(b-1)^n-(b+1)^n =(f)^n

where f depends on b.

for example

(x-1)^2-(x+1)^2 =-[4sqrt(x)]^2
 
  • #10
vvthuy said:
I meant, I tried to get the following form by expansion the left hand side of equation and then combine terms to get the right hand side

(b-1)^n-(b+1)^n =(f)^n

where f depends on b.

for example

(x-1)^2-(x+1)^2 =-[4sqrt(x)]^2

You can only do that in case of n<3 because, in this case, the number of terms of the series development (as shown in my preceeding post) is reduced to one.
If n>2, it is impossible to find a function f which do not depends of n.
(b-1)^n-(b+1)^n =(f(b,n))^n
 

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