Meson-loop contributions to the quark condensate from the instanton vacuum

We investigate the quark condensate of the QCD vacuum within the instanton vacuum model. We calculate the meson-loop contributions to the dynamical quark mass and quark condensate to $\mathcal{O}(1\mathrm{/}{N}_c)$-, $\mathcal{O}(m\mathrm{/}{N}_c)$-, and ${\cal O}((m\ln m) /N_c)$-order corrections. We find that the meson (especially pion) loops provide substantial contributions to the dynamical quark mass and as a result to the quark condensate. The results indicate that the $1\mathrm{/}{N}_c$ corrections should be reconsidered in the systematical way. The present results are consistent with those from chiral perturbation theory.