  Starting with a review of the thermal fluctuations in superconductors, the
Gaussian Effective Potential is shown to be a powerful variational tool for the
study of the breaking of symmetry in gauge theories. A novel re-derivation of
the massive expansion for QCD is presented, showing its variational nature and
its origin from the Gaussian potential that also provides a variational proof
for chiral symmetry breaking and dynamical generation of a gluon mass.
