Concerning green's function with the same time and spatial argument(i.e. ##G_0(x,t;x,t)##, mostly in QFT), I have the following question(adsbygoogle = window.adsbygoogle || []).push({});

1. Is green's function well defined at this point?

2. if green's function is well defined at this point, is it continuous here?

3. In quantum many body theory, I am instructed to view ##G_0(x,t;x,t)## as ##G_0(x,t;x,t+0^+)## in feynman diagrams. Why is this so?

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# Green's function with same time and spatial arguments

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