Rudin Ch 5, #29: Uniqueness Theorem for Systems of ODEs

  • Thread starter Quantumpencil
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In summary, the conversation discusses exercise 28 which involves considering a system of equations and deriving a uniqueness theorem for solutions of a given equation. The equation involves g_{j} and f as continuous real functions and is subject to initial conditions. The thread also includes a request to lock the thread and a link to the actual topic for help.
  • #1
Quantumpencil
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Homework Statement



Specialize exercise 28 by considering the system

[tex]\y'= y_{j+1} j=(1,...,k-1)
y'_{k}= f(x)-\sum g_{j}(x)y_{j} where the summation runs from j=1 to j=k, and g_{j} and f are continuous real functions on [a,b], and derive a uniqueness theorem for solutions of the equation

y^{k}+g_{k}(x)y^{k-1}+...+g_{2}y'+g_{1}(x)y = f(x)

subject to initial conditions

y(a)=c_{1}, y'(a)= c_{2}, y^{k-1}(a) = c_{k}.[\tex]



Homework Equations





The Attempt at a Solution


 
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  • #2
Hi Quantumpencil! :smile:

(you use the wrong slash: :wink:)
Quantumpencil said:
Specialize exercise 28 by considering the system

[tex]y'= y_{j+1}, j=(1,...,k-1),\ y'_{k}= f(x)-\sum g_{j}(x)y_{j}[/tex] where the summation runs from j=1 to j=k, and g_{j} and f are continuous real functions on [a,b], and derive a uniqueness theorem for solutions of the equation

[tex]y^{k}+g_{k}(x)y^{k-1}+...+g_{2}y'+g_{1}(x)y = f(x)[/tex]

subject to initial conditions

[tex]y(a)=c_{1}, y'(a)= c_{2}, y^{k-1}(a) = c_{k}[/tex]

Show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:
 
  • #3
yeah, so I didn't realize I made this thread; it's incomplete. Could I get it locked?

The actual thread I need help on is further-down and contains the good tech + information about how I think the solution will work out.

https://www.physicsforums.com/showthread.php?t=297047

This is the link to the actual topic.
 
Last edited:

1. What is the Uniqueness Theorem for Systems of ODEs?

The Uniqueness Theorem for Systems of ODEs states that for a system of differential equations with initial conditions, if the coefficients and the initial conditions are continuous functions, then there exists a unique solution to the system of equations in a certain interval.

2. How does the Uniqueness Theorem for Systems of ODEs differ from the Uniqueness Theorem for single ODEs?

The Uniqueness Theorem for Systems of ODEs applies to a system of equations, while the Uniqueness Theorem for single ODEs applies to a single equation. The main difference is that a system of equations has multiple dependent variables, while a single equation has only one dependent variable.

3. What is the importance of the continuity requirement in the Uniqueness Theorem for Systems of ODEs?

The continuity requirement ensures that the solution to the system of equations is well-behaved and does not have any sudden changes or discontinuities. This is important because it guarantees that the solution is unique and can be determined by the initial conditions.

4. Can the Uniqueness Theorem for Systems of ODEs be applied to non-linear systems?

Yes, the Uniqueness Theorem for Systems of ODEs can be applied to non-linear systems as long as the coefficients and initial conditions are continuous functions. However, the existence of a unique solution may be more difficult to prove in non-linear systems.

5. Are there any limitations to the Uniqueness Theorem for Systems of ODEs?

The Uniqueness Theorem for Systems of ODEs is only applicable to a certain interval where the initial conditions are specified. It also assumes that the coefficients and initial conditions are continuous functions. Additionally, the theorem only guarantees the existence of a unique solution, but it does not provide a method for finding the solution.

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