The Derivative Expansion of the Effective Action and the Renormalization Group Equation

The perturbative evaluation of the effective action can be expanded in powers of derivatives of the external field. We apply the renormalization group equation to the term in the effective action that is second order in the derivatives of the external field and all orders in a constant external field, considering both massless scalar ${\varphi }_4^4$ model and massless scalar electrodynamics. A so-called on shell'' renormalization scheme permits one to express this kinetic term’’ for the scalar field entirely in terms of the renormalization group functions appropriate for this scheme. These renormalization group functions can be related to those associated with minimal subtraction.