Auxiliary Field Meson Model at Finite Temperature and Density
  Starting from many quark interactions, we construct a nonlinear sigma-omega model at finite temperature and density. The mesons are introduced as auxiliary fields. Effective quark-meson couplings are strongly related to effective meson masses, since they are derived simultaneously from the original many quark interactions. In this model, even if the effective omega-meson mass decreases due to the partial chiral restoration, the equation of state (EOS) of nuclear matter can become soft. 
H. Kouno, T. Sakaguchi, K. Kashiwa, M. Hamada, H. Tokudome, M.   Matsuzaki and M. Yahiro