AVERAGE ACTION FOR MODELS WITH FERMIONS

The average action is a new tool for investigating spontaneous symmetry breaking in elementary particle theory and statistical mechanics beyond the validity of standard perturbation theory. The aim of this work is to provide techniques for an investigation of models with fermions and scalars by means of the average potential. In the phase with spontaneous symmetry breaking, the inner region of the average potential becomes flat as the averaging extends over infinite volume and the average potential becomes flat as the averaging extends over infinite volume and the average potential approaches the convex effective potential. Fermion fluctuations in this region necessitate a calculation of the fermion determinant in a spin wave background. We also compute the fermionic contribution to the wave function renormalization in the scalar kinetic term.