One-loop diagrams and vacuum stability in λφ4 theory

Abstract The relation between the stability analysis and the perturbative expansion for spontaneously broken λφ 4 theory is discussed. The stationarity conditions for the gaussian effective potential are shown to imply a simple one-loop resummation in the shifted theory, where the low energy effective coupling constant is O(λ 2 ) rather than λ, a value which refers to the interaction strength at the cutoff scale.