  Anomalous quantisation of instantons allows non-trivial (anti) self-dual
configurations to exist for pure U(2) gauge theory in four-dimensional
Euclidean space-time and to be used as ground state of the model. Six left
fermions together with six right fermions and one complex scalar doublet
describe the largest possible vacuum. This structure is just enough to
represent the leptons and Higgs boson in the Standard Model.
