Keller G. , Kopper Ch.
Renormalizability Proof for QED based on Flow Equations
(109K, TeX)

ABSTRACT.  We prove the perturbative renormalizability 
of Euclidean $QED_4$ using flow equations, i.e. with the aid of 
the Wilson renormalization group adapted to perturbation theory.
As compared to $\Phi^4_4$ the additional difficulty to overcome
is that the regularization violates gauge invariance. We prove that
there exists a class of renormalization conditions such that the 
renormalized Green functions satisfy the QED Ward identities 
and such that they are infrared finite at nonexceptional momenta. 
We give bounds on the
singular behaviour at exceptional momenta (due to the massless
photon) and comment on the adaptation to the case when the fermions
are also massless.