Chiral symmetry in perturbative QCD

We prove that the chiral symmetry of quantum chromodynamics with massless quarks is unbroken in perturbation theory. Dimensional regularization with γ5 = i γ0 γ1 γ2 γ3 is used. The ratio of the vector and axial vector renormalization constants is shown to be independent of the renormalization mass. The general results are explicitly verified to fourth order in g, the QCD coupling constant. (orig.)