Deriving the quark condensate within a finite Fermi system from the   generating functional of chiral perturbation theory
  The generating functional of heavy baryon chiral perturbation theory at order O(Q^2) in the mean field approximation (with a pseudoscalar source coupling which is consistent with the PCAC-Ward identities on the current quark level) has been exploited to derive Migdal's in--medium pion propagator. It is shown that the prediction for the density dependence of the quark condensate obtained on the composite hadron level by embedding PCAC within the framework of Migdal's approach to finite Fermi systems is identical to that resulting from QCD. 
Mariana Kirchbach (Uni Mainz) and Andreas Wirzba (TH Darmstadt)