Removing a Singularity for a Second Order ODE

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Discussion Overview

The discussion revolves around solving a second-order ordinary differential equation (ODE) with a singularity at a boundary condition. Participants explore methods to address the singularity and satisfy given boundary conditions, particularly focusing on the Bessel function solutions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses difficulty in removing the singularity at the boundary condition y'(0)=0 and seeks advice.
  • Another participant suggests that for nonzero x, the equation can be simplified, and any solution of the simplified equation is valid for the original equation.
  • A different participant notes the presence of a regular singular point at x=0 and proposes looking for a solution in the form of a power series.
  • One participant identifies the equation as a Bessel ODE and discusses the implications of the boundary conditions on the constants in the solution.
  • Another participant shares an expression for the Bessel function and mentions challenges in meeting the boundary conditions, questioning the validity of certain manipulations of k.
  • A later reply introduces a series solution involving the roots of the Bessel function and suggests a method to satisfy the boundary conditions through specific coefficients.

Areas of Agreement / Disagreement

Participants do not reach a consensus on how to effectively remove the singularity or satisfy the boundary conditions. Multiple competing views and approaches are presented without resolution.

Contextual Notes

Participants express uncertainty regarding the implications of the boundary conditions on the solutions and the validity of certain manipulations involving the parameter k. The discussion reflects various assumptions about the nature of the singularity and the behavior of the Bessel functions.

Who May Find This Useful

Readers interested in differential equations, particularly those involving singularities and Bessel functions, may find the discussion relevant.

DrChops
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I was given the following equation to solve:

x^2*y'' + x*y' + k^2*x^2*y = 0
B.C. y'(0)=0, y(1)=0

where k is just some constant.

I am having a hard time removing the singularity created by the boundary condition at y' and not aware of a method how. Any advice would be greatly appreciated.
 
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For x nonzero, you can obviously simplify the equation. When x is zero, there simply is no information from the DE. So any solution of the simplified equation is a valid solution for the original.
Please show your working so far.
 
Not sure what you mean by removing the singularity. You have a regular singular point at ##x=0##. Have you looked for a solution of the form$$
y=\sum_{n=0}^\infty x^{n+r}\hbox{?}$$
 
Hi !

it is a Bessel ODE:
y = c1*J0(k*x) +c2*Y0(k*x)
The condition y'(0)=0 implies c2=0, hence y(x) = c1*J0(k*x)
J(k)=0 only in case of some particular values of k.
So, generally, the condition y(1)=0 implies c1=0, hence y(x)=0 in general.
But, y(x)=c1*J0(k*x) in case of some particular values of k.
 
Thanks for all the help so far.
I'm just trying to express the Bessel function in a way that satisfies the boundary conditions. So far I have written it out to:
1- 1/4*k^2*x^2 + (.25*k^2*x^2)^2/4 - (1/4*k^2*x^2)^3/
36 + (.25*x^2*k^2)^4/24^2

Using equation 78 off this link http://mathworld.wolfram.com/BesselFunctionoftheFirstKind.html
My problem is that I can't get it to meet the boundary conditions. If I could take out the 1 and set "k" equal to about 5.3, it fits... but I think that's cheating.
 
Does this help:
Let ri be the ith +ve root of J1(x). So it also satisfies J0'(x) = 0.
Consider Y(x) = Ʃ aiJ0(rix)
This satisfies Y'(1) = 0.
If we can find ai s.t. Ʃairi2 = k2Ʃ ai then I believe Y satisfies the original equation, and Y'(0) = Ʃ airiJ0'(0) = 0
 

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