  Condensation energy in a superconductor cannot be precisely defined if
mean-field theory fails to hold. This implies that in the case of high
temperature superconductors, discussions of quantitative measures of
condensation energy must be scrutinized carefully, because the normal state is
anomalous and the applicability of a mean-field description can be questioned.
A related issue discussed here is the precise meaning of a superconducting
transition driven by kinetic as opposed to one driven by potential energy; we
argue that this is a semantic question.
