Integral from 0 to ∞ with singularity at x=0

RedSonja
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Here's an integral that is currently giving me grey hairs:

\int_0^{\infty} \frac{1}{x} \exp(i \frac{k}{x}(a-c \cos(\theta + wx))) dx

I've tried different approaches like contour integration around x=0 and replacing the exponential by its Taylor sum to have:

\int_0^{\infty} \sum_{n=0}^{\infty} \frac{1}{x^{n+1}\;n!} (i k (a-c \cos(\theta + wx)))^n dx

I can do the integrals of the even terms by \int_0^{\infty} = \frac{1}{2}\int_{-\infty}^{\infty} and residues, but I don't know how to handle the odd terms.

Going to sum-extremes I've rewritten the integral to a form where I only need to do integrals of the type

\int_0^{\infty} \frac{1}{x^{n+1}} e^{imwx} dx

with m a positive or negative integer, but even here I'm stuck. Please help!
 
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Maybe this is a stupid question, but is the integration over the real axis?
 
rollingstein said:
Maybe this is a stupid question, but is the integration over the real axis?

Yes, x is real. But since the integrand goes to zero for x\rightarrow \infty the direction of integration in the complex plane shouldn't alter the integral...
 
Hmm.
Is it possible that the latter of the three integrals is simply the gamma-function?
 
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