A quark meson coupling model with density- and temperature- dependent quark masses

Based on the quark mass density-and temperature-dependent model we suggest a model for nuclear matter where the meson field is introduced to be directly coupled to the quarks. The dynamic formation of the nucleon bag, the saturation properties of nuclear matter as well as equation of state for this model are studies. Relativistic calculation of infinite nuclear matter as well as neutron matter plays an important role in nuclear physics. The quantum hadrodynamics(QHD) models 1 based on baryon and meson degress of freedom form a reasonable starting point for the study of bulk as well as single-particle properties of nuclei. However, quantum chromodynamics(QCD) is believed to be essential in the study of nuclear phenomena from the quark structure of nucleon. It is also popular to describe nucleon, hyperon or strangelet in terms of bag models. The quark mass density-and temperature-dependent model(QMDTD) is an extension of the original quark mass density-dependent model(QMDD) 2. While the latter can almost reproduce the properties of quark matter obtained by the MIT bag model 3 , but it meets many difficulties when we extend this model to finite temperature 4. Based on Frieberg-Lee soliton bag models 5 , it is recognized that the bag constant B decreases with increasing temperature. It becomes zero and the nontopological solition solution dissappears at the phase transition point T c. This dynamic deconfinement mechanism is incorporated in the QMDTD model by introducing an ansatz B = B(T) = B 0 [1 − a(T /T c) + b(T /T c) 2 ], where B 0 is the vacuum energy density inside the bag at zero temperature , T c = 170M eV is the critical temperature of quark deconfinement phase transition, and a, b are two