Ok - so essentially the Feynman propogator is a Green function solved for a point source - i.e a delta function in 3 dims.(adsbygoogle = window.adsbygoogle || []).push({});

My question is more mathematical.

When you solve for the Green Function you assume

(id-m)G(x,x') = delta(x-x') (roughly)

Then solving this going through the standard process (Fourier Transforming RHS, performing integral etc) you come up with the Green function aka the Feynman propogator.

Now my question is this:

What is the original justification (for ALL Green function proplems actually) that the RHS is a delta function?? Why/How do you assume this and what is the physics meaning??

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# Origin of Feynman Propogator.

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