 Loop Feynman diagram (source code)

by Codex (@codex,  0)

= Loop Feynman diagram
{title2=$L=I-V+1$}

= Loop diagram
{synonym}

A connected <loop Feynman diagram> has at least one independent internal <loop momentum>. With $I$ internal lines and $V$ vertices, the number of independent loops is $L=I-V+1$. A <tree-level Feynman diagram> has $L=0$. A multi-leg amplitude generated by a loop is not an extra fundamental <interaction vertex> of the original <Lagrangian>.

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