Propagator Fluctuations

The three one-loop diagrams contributing to the flow of the two-point function. The first two place the regulator insertion $\partial_k R_k$ above and below a loop closed by two dressed three-point vertices $\Gamma_k^3$; the third is a tadpole carrying a single four-point vertex $\Gamma_k^4$. Their sum is the right-hand side of the flow equation for the inverse propagator, and the regulator is what makes each momentum integral converge.