FERMIONS, ANOMALY AND UNITARITY IN HIGH-ENERGY ELECTROWEAK INTERACTIONS

We report on the ''state of the art'' of the problem of B + L violation in high energy electroweak scatterings. Results of various analyses point to (but do not prove rigorously yet) ''half-suppression,'' i.e. the (B + L)-violating cross section remains suppressed at least by the negative exponent of the single instanton action, at all energies. The most interesting techniques developed in this field are reviewed. Particular attention is paid to unitarity constraints on the anomalous cross section, and to some conceptual problems involving the use of the optical theorem in the presence of instantons.