QUARK CONDENSATE IN NUCLEAR-MATTER

The quark condensate in nuclear matter is calculated with allowance fo r the pion field generated by one- and two-pion exchanges between nucl eons of the matter. The dependence of the condensate on the matter den sity rho is found. It is shown that, at very low densities, nonlinear terms are proportional to rho(2) and that they enhance the tendency to the restoration of chiral symmetry. At higher densities, the nonlinea r terms change sign, so that the in-medium interaction hinders the res toration of chiral symmetry according to the rule rho(4/3). The magnit ude of the condensate at equilibrium density is also calculated. The r ole of multinucleon effects is analyzed.