Determining Cauchy principal value of divergent integrals

In summary, the conversation discusses the difficulty of finding examples or problems in books that demonstrate how to find Cauchy principal values of divergent integrals. The person is specifically looking for examples of finding principal values of integrals involving sine and cosine functions. They mention that most examples only show how to find principal values of convergent integrals, where the contribution of the arc on the contour goes to zero, and the principal value equals the value of the integral. They eventually figure out the solutions to their problems and offer to share them with others.
  • #1
saybrook1
101
4

Homework Statement


So I've found a ton of examples that show you how to find cauchy principal values of convergent integrals because it is just equal to the value of that integral and you prove that the semi-circle contribution goes to zero. However, I need to find some Cauchy principal values of divergent integrals and I can't find any examples or even problems in any books that have these. Perhaps I'm just looking in the wrong place I'm not sure. If anyone could point me in the direction of any examples where principal values are found of divergent integrals that would be amazing, thank you.

Homework Equations


[tex]P.V. \int^{\infty}_{-\infty}\frac{sin2xdx}{x+4}[/tex]
[tex]P.V.\int^{\infty}_{-\infty}\frac{cos2xdx}{x^{2}-16}[/tex]

The Attempt at a Solution


I've gone through many examples but they just prove that the contribution of the arc on the contour goes to zero and so the principal value equals the value of the convergent integral. Any examples resembling my problems would be great.[/B]
 
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  • #2
Figured them out, if anyone wants the solutions let me know.
 

1. What is the Cauchy principal value of a divergent integral?

The Cauchy principal value of a divergent integral is a method of assigning a value to an integral that would otherwise be undefined due to divergence. It is defined as the limit of the integral as the limits of integration approach the point of divergence.

2. How do you determine the Cauchy principal value of a divergent integral?

To determine the Cauchy principal value of a divergent integral, you first need to rewrite the integral as a difference of two integrals. Then, take the limit of each integral as the limits of integration approach the point of divergence. Finally, take the difference of these two limits to obtain the Cauchy principal value.

3. Why is it necessary to use the Cauchy principal value for divergent integrals?

Divergent integrals have no defined value, and therefore cannot be solved using traditional integration methods. The Cauchy principal value allows us to assign a meaningful value to these integrals and use them in calculations and applications.

4. Can the Cauchy principal value of a divergent integral be negative?

Yes, the Cauchy principal value of a divergent integral can be negative. This occurs when the original integral has a positive and negative divergent part, and the Cauchy principal value is the difference between these two divergent parts.

5. Are there any limitations to using the Cauchy principal value for divergent integrals?

Yes, there are limitations to using the Cauchy principal value for divergent integrals. It can only be applied to integrals that can be rewritten as a difference of two integrals, and it may not always give a unique or satisfactory solution to the original integral.

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