The quark condensate is calculated within the world-line effective-action
formalism, by using for the Wilson loop an ansatz provided by the stochastic
vacuum model. Starting with the relation between the quark and the gluon
condensates in the heavy-quark limit, we diminish the current quark mass down
to the value of the inverse vacuum correlation length, finding in this way a
64%-decrease in the absolute value of the quark condensate. In particular, we
find that the conventional formula for the heavy-quark condensate cannot be
applied to the c-quark, and that the corrections to this formula can reach 23%
even in the case of the b-quark. We also demonstrate that, for an exponential
parametrization of the two-point correlation function of gluonic field
strengths, the quark condensate does not depend on the non-confining
non-perturbative interactions of the stochastic background Yang-Mills fields.Comment: 12 pages, 2 figures, to appear in Eur. Phys. J.
