Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Integration question in Peskin and Schroeder

  1. Aug 3, 2012 #1
    Hi all, I'm stuck with proving the last step of (2.51) in Peskin and Schroeder:
    $$\begin{align} D(x-y) &= \frac{1}{4\pi^2}\int^\infty_m dE \sqrt{E^2 - m^2}e^{-iEt}\\
    & \approx_{t \to \infty}\ \ e^{-imt}\end{align}$$

    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,

  2. jcsd
  3. Aug 4, 2012 #2


    User Avatar
    Science Advisor

  4. Aug 4, 2012 #3
    Thanks strangerep,

    The thread I referred to was https://www.physicsforums.com/showthread.php?t=424778.

    Your post does make it clearer, in that it stems from a limit of the exact solution (Bessel function). I will look through the details soon.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook