Showing That the Modified Bessel Function of the First Kind is a Solution

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Discussion Overview

The discussion revolves around demonstrating that the modified Bessel function of the first kind, I_v(x), is a solution to the modified Bessel equation. Participants are engaged in mathematical reasoning and verification of their calculations related to the equation.

Discussion Character

  • Mathematical reasoning

Main Points Raised

  • One participant presents their work on differentiating the modified Bessel function and substituting it into the modified Bessel equation, expressing skepticism about their end result.
  • A subsequent post clarifies the actual left-hand side of the equation, indicating it involves terms multiplied by (x/2)^(2k+v) within a summation.
  • Another participant questions the validity of the second term when k=0, noting that it leads to an undefined expression due to the factorial of -1.
  • A later reply acknowledges a mistake in changing the index, which resulted in an incorrect denominator, but mentions obtaining a series that converged to 0.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the correctness of their calculations and the implications of undefined terms, indicating that multiple views on the validity of the steps remain unresolved.

Contextual Notes

Participants note issues related to the convergence of series and the handling of undefined terms, but do not resolve these concerns.

womfalcs3
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Hello,

I am in the process of showing that the modified Bessel function, I_v(x), is a solution to the modified Bessel equation,

x^2*y''+x*y'-(x^2+v^2)*y=0

I have differentiated the MBF twice and plugged it into show that the left hand side is in fact 0.

After a good amount of work, I've come to the following left hand side:

10shj0o.jpg


Where sigma=v.


Is that right? The math seems straight forward, and I only did one change of index that looks correct to me. I'm skeptical about the end result though.
 
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Sorry, the actual left hand side I have are those two terms inside the sum multiplied by (x/2)^2k+v.

All inside the sum.
 
womfalcs3 said:
Hello,


10shj0o.jpg


Is that right? The math seems straight forward, and I only did one change of index that looks correct to me. I'm skeptical about the end result though.

Not sure either. But the second term is undefined when k=0 , i.e. (-1)! = Γ(0) is undefined. Or do we assume the second term to be zero?
 
matematikawan said:
Not sure either. But the second term is undefined when k=0 , i.e. (-1)! = Γ(0) is undefined. Or do we assume the second term to be zero?

Thank you for the response.

I just realized I made a mistake by changing the index, resulting in that denomintor. I eventually obtained a series that converged to 0.

Thank you again.
 

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