Conformal invariance in gauge theories. I. Quantum electrodynamics

The present cycle of studies is based on the assumption that gauge fields transform in accordance with nonprincipal representations of the conformal group. As a consequence, it is shown that the conformally invariant two-point functions have nontrivial transverse parts. Conformal quantum electrodynamics is considered in this, the first paper. A nondegenerate conformally invariant Lagrangian of the free electromagnetic field is constructed, and the validity of canonical quantization is verified. The physical subspace is distinguished in an invariant manner. The inclusion of an interaction with an external current is discussed.