Singular defects with fractional topological charge in σ models and gauge theories

Abstract

A novel class of self-dual solutions in σ models and gauge theories is considered. The contribution of the corresponding fluctuations to the chiral condensate is calculated. We discuss the few tightly connected problems, such as the U(1) problem, the θ dependence and the chiral symmetry breaking within a framework of this approach. Arguments in favour of significance of the configurations with fractional topological charge are given.