Thermodynamics of strange quark matter with the density-dependent bag constant

Abstract

The thermodynamics of strange quark matter with density dependent bag constant are studied selfconsistently in the framework of the general ensemble theory and the MIT bag model. In our treatment, an additional term is found in the expression of pressure. With the additional term, the zero pressure locates exactly at the lowest energy state, indicating that our treatment is a self-consistently thermodynamic treatment. The self-consistent equations of state of strange quark matter in both the normal and color-flavor-locked phase are derived. They are both softer than the inconsistent ones. Strange stars in both the normal and color-flavor locked phase have smaller masses and radii in our treatment. It is also interesting to find that the energy density at a star surface in our treatment is much higher than that in the inconsistent treatment for both phases. Consequently, the surface properties and the corresponding observational properties of strange stars in our treatment are different from those in the inconsistent treatment.