Feynman Diagrams Loop Regulator

physicsquantum field theoryFeynman diagramsloop correctionspropagatorsquantum fluctuationsregulator insertioncetztikz

Two Feynman diagrams showing loop corrections to a propagator. Each diagram contains a loop with momentum q₀ and two external lines with coupling g. The loops include mass terms m₁², m₂² and width terms γ₁², γ₂². The diagrams differ in the position of the regulator insertion (cross marker) which appears at the bottom vertex in the first diagram and at the top in the second.