Action Ward Identity and the Stueckelberg-Petermann renormalization group

A fresh look at the renormalization group (in the sense of Stueckelberg-Petermann) from the point of view of algebraic quantum field theory is given, and it is shown that a consistent definition of local algebras of observables and of interacting fields in renormalized perturbative quantum field theory can be given in terms of retarded products. The dependence on the Lagrangian enters this construction only through the classical action. This amounts to the commutativity of retarded products with derivatives, a property named Action Ward Identity by Stora.