Strange quark stars within the Nambu-Jona-Lasinio model - art. no. 043005

We investigate the properties of charge-neutral beta -equilibrium cold quar k matter within the Nambu-Jona-Lasinio model. The calculations are carried out for different ratios of coupling constants characterizing the vector an d scalar 4-fermion interaction xi =G(v)/G(s). It is shown that for xi <0.4 matter is self-bound and for <xi><0.65 it has a first order phase transitio n of the liquid-gas type. The Gibbs conditions in the mixed phase are appli ed for the case of two chemical potentials associated with the baryon numbe r and electric charge. The characteristics of the quark stars are calculate d for <xi>=0, 0.5, and 1. It is found that the phase transition leads to a strong density variation at the surface of these stars. For xi = 1 the prop erties of quark stars show behaviors typical for neutron stars. At xi great er than or similar to 0.4 the stars near to the maximum mass have a large a dmixture of strange quarks in their interiors.