NUCLEON SIGMA TERM AND IN-MEDIUM QUARK CONDENSATE IN THE MODIFIED Quark–MESON COUPLING MODEL

We evaluate the nucleon sigma term and in-medium quark condensate in the modified quark–meson coupling model which features a density-dependent bag constant. We obtain a nucleon sigma term consistent with its empirical value, which requires a significant reduction of the bag constant in the nuclear medium similar to those found in the previous works. The resulting in-medium quark condensate at low densities agrees well with the model-independent linear order result. At higher densities, the magnitude of the in-medium quark condensate tends to increase, indicating no tendency towards chiral symmetry restoration.