In gauge theory, Higgs fields are responsible for spontaneous symmetry
breaking. In classical gauge theory on a principal bundle P, a symmetry
breaking is defined as the reduction of a structure group of this principal
bundle to a subgroup H of exact symmetries. This reduction takes place iff
there exists a global section of the quotient bundle P/H. It is a classical
Higgs field. A metric gravitational field exemplifies such a Higgs field. We
summarize the basic facts on the reduction in principal bundles and geometry of
Higgs fields. Our goal is the particular covariant differential in the presence
of a Higgs field.Comment: 11 page