FERMIONS, ANOMALY AND UNITARITY IN HIGH-ENERGY ELECTROWEAK INTERACTIONS

We report on the ''state of the art'' of the problem of B + L violatio n 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. Th e most interesting techniques developed in this field are reviewed. Pa rticular attention is paid to unitarity constraints on the anomalous c ross section, and to some conceptual problems involving the use of the optical theorem in the presence of instantons.