Properties of quark matter within the self-consistent quasi-particle model

The baryon number density serves as a key macroscopic parameter that governs the thermodynamic properties of cold quark matter. In this work, we employ the improved quasi-particle model to investigate the ground-state thermodynamic behavior of QCD matter. After obtaining a meaningful partition function, we proceed to compute the pressure and energy density of quark matter at zero temperature. We therefore study the dependence of the speed of sound on baryon number density and find that the speed of sound approaches 1/3 in the high baryon number density regime. In addition, we calculate the energy per baryon as a function of the baryon number density. It is found that the pressure is nearly zero at the minimum of the energy per baryon for both 2-flavor and (2+1)-flavor cold quark matter, which agrees with the theoretical prediction on thermodynamic consistency in quark matter by Xia et al. (Phys. Rev. D 89, 105027 (2014)).