ODE Existence/Uniqueness Intervals

In summary, for the given function f(x,y) = e^(- (y-x)^2), a unique solution exists for intervals x∈[0,t*] on the rectangle B = [0,a]x[-b,b], where t* = b/(max|f(x,y)|). To find the maximum value of f(x,y), one can substitute p = y-x and find the maximum value of e^(-p^2).
  • #1
middleramen

Homework Statement



Obtain intervals x∈[0,α] for the existence of a unique solution

dy/dx = f(x,y) = e^-(y-x)^2; y(0) = 0

on the rectangle B = [0,a]x[-b,b]

Homework Equations


The Attempt at a Solution



Since both dy/dx and it's partial derivative of y are both continuous, a unique solution exists. Thus an interval for existence for t is [0,t*], where t* = b/(max|f(x,y)|).

I'm not sure how to determine max|f(x,y)|.

Any help is appreciated.
 
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  • #2
f(x,y) = e^(- (y-x)^2), correct? In that case, it seems to me that it would be easier to temporarily define a new variable, say, p = y-x, and substitute that in. From there, it's easy to find the maximum value of e^(-p^2).
 

What is the definition of existence/uniqueness intervals for ODEs?

The existence/uniqueness interval for an ordinary differential equation (ODE) refers to the interval of values for the independent variable over which the solution to the ODE is guaranteed to exist and be unique. This interval is determined by the initial conditions and the properties of the ODE itself.

What is the importance of existence/uniqueness intervals in ODEs?

The existence/uniqueness interval is important because it ensures the well-posedness of the ODE. This means that there is a unique solution that can be determined using the given initial conditions. Without this interval, the solution to the ODE may not exist or may not be unique.

How can one determine the existence/uniqueness interval for a given ODE?

The existence/uniqueness interval for a given ODE can be determined by analyzing the coefficients and properties of the ODE. In some cases, it may also be necessary to use specific theorems and techniques, such as the Cauchy-Lipschitz theorem, to determine this interval.

What happens if the initial conditions fall outside of the existence/uniqueness interval?

If the initial conditions fall outside of the existence/uniqueness interval, then the solution to the ODE may not exist or may not be unique. In this case, it may be necessary to redefine the initial conditions or analyze the ODE further to determine a different existence/uniqueness interval.

Are there any limitations to the concept of existence/uniqueness intervals for ODEs?

Yes, there are limitations to the concept of existence/uniqueness intervals for ODEs. In some cases, the interval may not exist or may be infinite, making it difficult to determine the solution to the ODE. Additionally, this concept only applies to first-order ODEs and may not be applicable to higher-order ODEs.

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