Integral of form e^(x)/(x^2+a^2)

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Homework Help Overview

The original poster is working on converting a single-dimension wavefunction to its momentum representation, focusing on a specific integral involving an exponential function divided by a quadratic expression.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster has attempted integration by parts and trigonometric substitution but is struggling with the resulting expressions. Some participants suggest using complex integration and the residue theorem, while others reflect on the prerequisites of Fourier analysis in relation to complex analysis.

Discussion Status

The discussion is ongoing, with various approaches being explored. Some participants have offered guidance on methods involving complex analysis, while the original poster expresses a need to revisit foundational concepts.

Contextual Notes

The original poster notes a significant gap in their knowledge of complex analysis, having not used it since their course five years ago. This context may influence their ability to engage with the suggested methods effectively.

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Homework Statement


I'm working on converting a single-dimension wavefunction to its momentum representation. Here is the integral I am stuck with (I've pulled out some constants):
\int\limits_{-\infty}^{\infty}\frac{e^{\frac{-ipx}{\hbar}}}{x^2+a^2}\textrm{d}x


Homework Equations


Integration by parts, x = atanθ, e^iθ = cosθ + isinθ


The Attempt at a Solution


I've tried integrating by parts, but the problem is I always get something nasty multiplied by an exponential and I can't seem to make them get along. I've also tried Euler's formula, but that doesn't seem to help me either (I end up with something like cos(tanθ)dθ after trying to make a trig substitution to get the 1/(x^2 + a^2) part to behave.
Any ideas?
 
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Use the methods of complex integration and the residue theorem by taking a semi-circular contour depending on the sign of p.
 
Apparently, where I come from, rumor has it that you can't study Fourier analysis* without going through complex analysis before.

*and its applications to physical sciences.
 
I'm a grad student in ECE and it's been about 5 years since I took a complex analysis course. Unfortunately, I didn't use any of it after the class, so I'm more than a little rusty. Time to whip out some old textbooks and start digging.
Thanks!
 

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