# Feynman diagram and uncertainty

I have been introduced to the Feynman diagrams in QFT after following Wick-Dyson tedious formalism.

Two things are unclear, though, about the Feynman shortcut to compute scattering amplitudes.

What are the horizontal and vertical axes in these diagrams? Are they $x$ and $t$ respectively or $x$ and $y$?

If yes then we are drawing a particle with an exact momentun $p$.

But doesn't this violate the uncertainty principle since we are assuming exactly measured $x$ and $p$?

• At each vertex of Feynman diagrams momentum conservation is ensured by Dirac delta function. – Mass Dec 6 '16 at 17:37
• I mean consider an external leg in the Feynman diagram. Are both momentum and position exactly measured? – user56963 Dec 6 '16 at 17:39
• Normally, the external legs represent momentum states of the particles, so their position is undetermined. As @AccidentalFourierTransform points out in their answer, position on a Feynman diagram does not represent position or time. The graph connections are what matter - not the locations of the nodes. – apdnu Dec 6 '16 at 20:42