Weak and electromagnetic contributions to quark masses

We study the lowest-order electromagnetic and weak contributions to quark masses in quantum chromodynamics. We review the arguments that these quantities are ultraviolet divergent in perturbation theory. A suggestion due to Brodsky, Schmidt, and de Teramond, based on a study of the Dyson equation for the quark self-energy, that electroweak corrections are controlled by low-energy physics if the number of quark flavors is greater than 10, is investigated. The meaning of the electromagnetic mass shift defined by these authors is clarified. In models possessing natural relations among quark masses and spontaneous symmetry breakdown the prescription of these authors is shown to lead to the same results as those of conventional analyses. In particular, corrections to these relations remain sensitive to the symmetry-violating scale for any number of quark flavors