Introduction to the Functional Renormalization Group

The renormalization group (RG) has nowadays achieved the status of a meta-theory, which is a theory about theories. The theory of the RG consists of a set of concepts and methods which can be used to understand phenomena in many different fields of physics, ranging from quantum field theory over classical statistical mechanics to nonequilibrium phenomena. RG methods are particularly useful to understand phenomena where—uctuations involving many different length or time scales lead to the em...