Hi all, I'm stuck with proving the last step of (2.51) in Peskin and Schroeder:(adsbygoogle = window.adsbygoogle || []).push({});

$$\begin{align} D(x-y) &= \frac{1}{4\pi^2}\int^\infty_m dE \sqrt{E^2 - m^2}e^{-iEt}\\

& \approx_{t \to \infty}\ \ e^{-imt}\end{align}$$

I've read on another post that the solution is to use the method of stationary phase, but I do not see how this applies, as [itex]E[/itex] is not a rapidly oscillating function...?

Thoughts appreciated,

Ianhoolihan

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# Integration question in Peskin and Schroeder

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