Editing Feynman diagram (section)

=== Feynman rules ===
The diagrams are drawn according to the Feynman rules, which depend upon the interaction Lagrangian. For the [[Quantum electrodynamics|QED]] interaction Lagrangian
:<math>L_v=-g\bar\psi\gamma^\mu\psi A_\mu</math>
describing the interaction of a fermionic field {{mvar|ψ}} with a bosonic gauge field {{mvar|A<sub>μ</sub>}}, the Feynman rules can be formulated in coordinate space as follows:

* Each integration coordinate {{mvar|x<sub>j</sub>}} is represented by a point (sometimes called a vertex);
* A bosonic [[propagator]] is represented by a wiggly line connecting two points;
* A fermionic propagator is represented by a solid line connecting two points;
* A bosonic field <math>A_\mu(x_i)</math> is represented by a wiggly line attached to the point {{mvar|x<sub>i</sub>}};
* A fermionic field {{math|''ψ''(''x<sub>i</sub>'')}} is represented by a solid line attached to the point {{mvar|x<sub>i</sub>}} with an arrow toward the point;
* An anti-fermionic field {{math|{{overline|''ψ''}}(''x<sub>i</sub>'')}} is represented by a solid line attached to the point {{mvar|x<sub>i</sub>}} with an arrow away from the point;