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May 12, 2021 at 15:40 comment added QFT addict. Where you from @ Buraian
May 12, 2021 at 15:31 vote accept QFT addict.
May 12, 2021 at 14:23 comment added Brian Nice to see another user from Kerela :)
May 12, 2021 at 14:16 answer added Vladimir Kalitvianski timeline score: 0
May 12, 2021 at 14:04 answer added QFT addict. timeline score: 1
May 10, 2021 at 18:41 comment added QFT addict. I made a small edit and make the question as Feynman propagator's particular case such that $x^0>y^0$, could you please tell now how the virtual particles associated with the above propagator be off-shell? @ Zack
May 10, 2021 at 18:35 history edited QFT addict. CC BY-SA 4.0
added 9 characters in body
May 9, 2021 at 21:42 comment added QFT addict. Please refer Eq 2.50 and 2.58 of Peskin and Shroeder@ Zack
May 9, 2021 at 21:29 comment added Zack It's because you incorrectly evaluated the contour integral. Recall from Jordan's lemma that you must close integrals of the form $f(z) e^{i k z}$ in the upper-half plane, while you must close integrals of the form $f(z) e^{-i k z}$ in the lower-half plane. For you, this mean that you pick up a pole with residue $+E_{\vec{p}}$ or $-E_{\vec{p}}$ depending on whether $x^0 - y^0$ is positive or negative. The details are readily available in any QFT textbook -- I recommend chapter 2 of Peskin and Schroeder.
May 9, 2021 at 21:12 comment added QFT addict. Could you please write, between which step the integration has an error? if need I can add more steps in between the integrals. @ Peter Kravchuk
May 9, 2021 at 20:49 comment added Peter Kravchuk The two functions are clearly different: while the first integral solves the wave equation $(\partial^2+m^2)\Delta_F(x-y)\propto\delta(x-y)$, the second solves $(\partial^2+m^2)\Delta_F(x-y)=0$. (Because $a\times 1/a=1$ and $a\times \delta(a)=0$.)
May 9, 2021 at 20:32 history edited Qmechanic CC BY-SA 4.0
edited body; edited tags
May 9, 2021 at 20:01 comment added QFT addict. Where it is?@Zack
May 9, 2021 at 20:00 comment added Zack Oops, I made a typo -- I meant to say that your integration is INcorrect!
May 9, 2021 at 19:58 comment added QFT addict. Yeah, It's the matter of flipping the contour in the upper and lower half-planes, the real question here is regarding the virtual particles and it's Mass shell connections, could you give some comments regarding this? @Zack
May 9, 2021 at 19:45 comment added Zack Your integration of the Feynman propagator is correct -- you've implicitly assumed that $x^0 > y^0$.
May 9, 2021 at 18:51 history asked QFT addict. CC BY-SA 4.0