The principle of minimal sensitivity applied to a new perturbative scheme in quantum field theory

A recently proposed perturbative method for solving a self-interacting scalar phi4 field theory consists of writing the interaction as gphi2(1+phi) and expanding in powers of δ. The method contains an ambiguity in so far as one could modify the interaction Lagrangian by a factor λ(1-phi). The truncated expansion depends on the unphysical parameter, whereas the exact result does not. The authors exploit this ambiguity by assigning to λ the value for which the truncated result is stationary, thus minimizing its sensitivity to λ. The technique is applied to field theories in zero- and one-dimensional space-times and gives improved accuracy as compared to fixed λ