Equation Of State From Hadronic Matter To Quark Matter In Neutron Stars

Neutron stars are excellent laboratories for studying high density matter in Quan-tum Chromodynamics(QCD).The structure of these stars as described by the Tolman-Oppenheimer-Volkoff(TOV)equation is directly related to the underlying equation of state.QCD equations of state are soft at nB?2n0 but must be stiff at nB>5n0.At low baryon density of nB?2n0,we apply the purely hadronic equation of state which is consistent with neutron stars of radii<13km and at high density nB?5n0 we apply the quark equation of state which must be stiff to support the two solar mass of neutron stars.In between the low and high density regions contain matter which cannot be described by using a purely hadronic or quark matter equation of state.In constructing the equation of state used in this paper,the low and high density equa-tions of state are interpolated while requiring that the interpolated equation of state must be thermodynamically well-defined and causal.Then we get a new constraint on quark equa-tion of state by considering the consistency with symmetric nuclear matter.We investigate the behavior of beta-equilibrated matter-QCD matter with respect to electromagnetic interaction and symmetric nuclear matter-QCD matter without electromagnetic interac-tion at low and high densities.We find out that at low density,both symmetric nuclear matter and beta-equilibrated matter have different equations of state but at high density,they approach the same quark matter equation of state.This indicates that in neutron star interiors,QCD matter with or without electromagnetic interaction makes no difference at high densities.