Lippmann-Schwinger equation

  • Thread starter Manojg
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Hi,

I have a simple question.
I am looking at Sakurai's "Modern Quantum Physics, Revised edition" on page 382 where he tries to integrate the Lippmann-Schwinger equation. From equation 7.1.15 to 7.1.16, he converted from Cartesian to spherical coordinate system. After integration over [tex]\phi[/tex] and [tex] cos\theta[/tex], he changed the integration over "q" (which is radius in spherical system) from "0 to +infinity" to "-infinity to +infinity".

One can't change radius from -infinity to +infinity in spherical coordinate, right? Then, how did he get that equation?

Thanks.
 

Answers and Replies

  • #2
Bill_K
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I don't have the book, but sure you can do that if the integrand is even. Doesn't mean there is anything physical about negative r, it's just a formal way of evaluating the integral. Maybe what comes next is a contour integration in the complex r plane?
 

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