Some features of hot and dense gas of quarks which are considered as the
quasi-particles of the model Hamiltonian with four-fermion interaction are
studied. Being adapted to the Nambu-Jona-Lasinio model this approach allows us
to accommodate a phase transition similar to the nuclear liquid-gas one at the
proper scale. It allows us to argue an existence of the mixed phase of vacuum
and baryonic matter (even at zero temperature) as a plausible scenario of
chiral symmetry (partial) restoration.Comment: 9 pages, 4 figures, RevTex version with some improvements and new
reference