Applying Boundary Conditions in Homogeneous ODE Problems

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SUMMARY

The discussion focuses on solving a homogeneous ordinary differential equation (ODE) of the form {u}''(x) + 2{u}'(x) + λu(x) = 0 with boundary conditions u(0) = u(1) = 0. The participants explore the implications of different values of λ, specifically λ < 1, λ = 1, and λ > 1, and how to apply boundary conditions to determine the eigenvalues and eigenfunctions. The general solution involves hyperbolic functions, leading to the conclusion that C must equal 0 when applying the first boundary condition, while D remains undetermined until the second boundary condition is applied.

PREREQUISITES
  • Understanding of homogeneous ordinary differential equations (ODEs)
  • Familiarity with boundary value problems and eigenvalue problems
  • Knowledge of hyperbolic functions, specifically sinh and cosh
  • Ability to manipulate exponential functions and apply boundary conditions
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  • Study the application of boundary conditions in solving ODEs
  • Learn about eigenvalue problems in the context of Sturm-Liouville theory
  • Explore the properties and applications of hyperbolic functions in differential equations
  • Investigate the implications of different parameter values (λ) on the solutions of ODEs
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Mathematicians, physicists, and engineering students involved in solving differential equations, particularly those focusing on boundary value problems and eigenvalue analysis.

  • #31
Fantastic. Didn't see that at all. Thanks very much!

For \lambda=1 \Rightarrow u(x)=e^{-x}[Ax+B]
So u(0)=0 \Rightarrow B=0 and u(1)=0 \Rightarrow A=0 and therefore u(x)=0

For \lambda&gt;1 \Rightarrow u(x)=e^{-x}[A\cos (\sqrt{\lambda-1})x+B\sin (\sqrt{\lambda-1})x]
So u(0)=0 \Rightarrow A=0 and u(1)=0 \Rightarrow either B=0 or \sin (\sqrt{\lambda-1})=0 \Rightarrow (\sqrt{\lambda-1})=n\pi

So the eigenvalues are \lambda =1+\pi^{2}n^{2}
And the eigenfunctions are u(x)=Be^{-x}\sin (n\pi x)

All correct?
 
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  • #32
Yes, it looks correct:smile:

ehild
 
  • #33
Great. Thanks so much for all your help!
I'm pleased to put this one to bed and come out having cleared some things up.
Cheers!
 

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