Essence of the vacuum quark condensate
  We show that the chiral-limit vacuum quark condensate is qualitatively
equivalent to the pseudoscalar meson leptonic decay constant in the sense that
they are both obtained as the chiral-limit value of well-defined
gauge-invariant hadron-to-vacuum transition amplitudes that possess a spectral
representation in terms of the current-quark mass. Thus, whereas it might
sometimes be convenient to imagine otherwise, neither is essentially a constant
mass-scale that fills all spacetime. This means, in particular, that the quark
condensate can be understood as a property of hadrons themselves, which is
expressed, for example, in their Bethe-Salpeter or light-front wavefunctions.
